Extragenital and Extrapelvic Endometriosis: Literature Update and Mri Immaging Case Collection of Unusual Localizations

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It manifests in three patterns: superficial peritoneal lesions, ovarian endometriomas, and deep infiltrating endometriosis. Our aim is to remind radiologists of the possibility of atypical locations of pelvic and extrapelvic endometriosis and to illustrate their characteristics on magnetic resonance imaging. The most common site of endometriosis is the ovaries, followed by the pelvic peritoneum. Less common locations include deep subperitoneal tissues, the gastrointestinal tract, the bladder, the thorax, and subcutaneous tissues. We present three rare clinical cases: diaphragmatic endometriosis, inguinal canal endometriosis, and a case of sciatic nerve infiltration. MRI imaging provides important findings that help classify the disease and identify the extent of the lesion, thus facilitating appropriate diagnosis and treatment. Radiologists should be familiar with the MRI imaging findings of deep infiltrating endometriosis in various anatomical sites to provide information that allows for adequate pre-surgical counseling. Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction Endometriosis is a prevalent gynecologic pathology estimated to affect 10% of women [ 1 ] and is defined by the ectopic presence of endometrial tissue outside the uterine cavity with consequent recurrent intralesional bleeding and resulting fibrosis. Feldman et al. discerned three forms of pelvic endometriosis: (a) superficial peritoneal lesions; (b) ovarian endometrioma; (c) deep (or solid infiltrating) endometriosis (\), histologically identified as a lesion that extends more than 5 mm into the sub peritoneal space or involving the walls of pelvic organs and ligaments [ 1 ]. Preeminent sites for endometriotic lesions include the ovaries, pelvic peritoneum, uterosacral ligaments, and torus uterine [ 2 ]. Atypical pelvic endometriosis localizations can occur in the cervix, vagina, round ligaments, ureter, and nerves. Moreover, rare extra pelvic endometriosis implants can be localized in the upper abdomen, subphrenic fold or in the abdominal wall. While characteristic symptoms comprise secondary dysmenorrhea and cyclic or persistent pelvic pain, the diagnostic context is often non-specific, contributing to a notable diagnostic delay of up to 10 years [ 1 – 3 ]. Unusual sites of endometriosis may be associated with specific symptoms depending on different localizations [ 4 ]. Extra pelvic compartments include right bowel structures (cecum, ileum, and appendix), sigmoid colon, lumbopelvic ureter, abdominal wall as well as umbilicus, and external part of inguinal canal [ 5 ], diaphragm and this paper explores three rare endometriosis localizations, highlighting their Magnetic Resonance Imaging (MRI) and clinical features in cases involving the sciatic nerve, diaphragm and abdominal wall. 2. Endometriosis non-invasive diagnosis 2.1 role of MRI and MRI features MRI is a useful noninvasive tool used to diagnose endometriosis because of the absence of ionizing radiation, multiplanar projections, and high contrast resolution with high sensitivity for detection of hemorrhagic lesions [ 6 ]. According to the guidelines established by the European Society of Urogenital Radiology (ESUR), the paramount indication for MRI lies in the examination of deep endometriosis. ESUR further advocates for MRI utilization in cases marked by positive clinical features but negative ultrasonography (US) results, as well as in presurgical planning and as a second-line test when US proves inconclusive [ 2 – 7 ] Nowadays, imaging techniques, including MRI and transvaginal ultrasound, have reached high diagnostic accuracy in detecting endometriosis; several papers demonstrated high agreement between imaging and surgical findings [ 8 – 9 ]. This is also mentioned in the recent ESHRE guidelines [ 10 ], which highlight that surgery is no longer the gold standard method to diagnose endometriosis and imaging can be used for the diagnosis and for the consequent management of patients without the need for diagnostic surgery. The SEF (Stiftung Endometriose-Forschung; Scientific Endometriosis Foundation) published in the 2003 and 2005 the ENZIAN classification, which established a useful tool for DIE classification focused also on MRI [ 11 ]. The latest revision of the ENZIAN score 2020 proposes a new comprehensive classification system, which includes the anatomical location and the size of the different forms of endometriotic lesions, the presence of adhesions, and the degree of involvement of the adjacent organs [ 12 ]. Recent ESUR guidelines do not provide specific recommendations regarding the timing of MRI in relation to the menstrual cycle [ 7 ]. Regarding technical recommendations, the application of fat saturation is advised for enhanced precision. Chemical frequency-selective fat saturation, targeting the high signal intensity inherent to fat tissue, proves instrumental in accentuating distinctions among non-fat T1-weighted hyperintense structures, thereby amplifying the visibility of minute hemorrhagic lesions associated with endometriosis [ 2 ]. On MRI, deep pelvic endometriosis manifests as hemorrhagic cysts or plaques, exhibiting hyperintensity in T1-weighted sequences, as well as solid or fibrous lesions characterized by low signal intensity on both T1- and T2-weighted images, indicative of an infiltrating behavior. High-resolution T1 and T2-weighted images are employed for meticulous evaluation, particularly when lesions involve ligaments and the subperitoneal space (> 5mm under peritoneal sierosa). Discrimination between endometriotic tissue with hemorrhagic content and fibrosis is achievable through MRI [ 3 – 13 ]. In advanced stages, endometriosis is often associated with adhesions, appearing as spiculated bands of low to intermediate signal intensity on T1- and T2-weighted imaging. These adhesions can obscure the interfaces between organs, leading to atypical imaging characteristics such as peritoneal space obliteration, fixed fluid accumulations, and distortion or displacement of nearby organs. To enhance visualization, axial, coronal, and sagittal planes are typically used, with oblique planes aligned to the affected organs providing additional information. [ 2 ]. In conclusion, MRI is essential to giving an exhaustive DIE roadmap, necessary in preoperative decision making, particularly in cases of extra pelvic disease where transvaginal US (first line imaging) also performed by expert operators is not accurate [ 5 ]. 2.2 MRI acquisition protocol As described above endometriosis is a multifocal and systemic disease and MRI allows complete evaluation of every abdominal compartment, identifying and mapping all types of endometriosis lesions within a single study [ 5 ]. At our institution, MRI were acquired with high field-strength (3 Tesla) systems, acquisition of axial, coronal and sagittal T2-weighted images and spin-echo or gradient-echo axial T1-weighted images obtained with or without fat suppression, with a slice thickness of 3 mm. In addition, in selected and atypical cases, axial T1-weighted images were obtained after intravenous administration of a gadolinium-based contrast agent. The usefulness of intravenous gadolinium injection to characterize endometriosis is still under discussion. Incidentally, international recommendations assert that the utilization of contrast agents typically does not contribute substantially to the initial diagnostic information [ 14 ]. In our hospital, we administer contrast medium agents solely when deemed beneficial for diagnosis. Nevertheless, it is deemed mandatory in cases where malignant transformation of endometrioma is suspected, as highlighted by Schneider at al. [ 14 ]. MRI with vaginal opacification using sonographic gel is recognized as a viable option for evaluating deep pelvic endometriosis. Some papers recommended MRI with gel opacification of vagina for studying usual localization of deep infiltrating endometriosis, particularly for the added value in evaluation of recto-vaginal septum, utero-sacral ligaments and posterior vaginal fornix. [ 15 ]. It's important to note that in our recent practice, we refrain from the practice of distending the vagina with sonographic gel [ 6 ]. 3. Unusual localization of extragenital endometriosis and case reports Renal endometriosis occurs in approximately less than 1% of all cases. Flank pain, haematuria and renal mass are the most common presentations of renal endometriosis, and it is sometimes misdiagnosed as renal cell carcinoma on imaging [ 16 ]. In case of symptoms, MRI is mandatory, to clarify the extent of the lesion and the depth of lesion invasion and to plan adequate surgical treatment [ 17 – 18 ]. Patients with thoracic endometriosis (TE) usually present with the triad of pain, pneumothorax and haemoptysis [ 19 ]. CT and MRI are the primary imaging modalities used for TE. While CT lacks specificity for TE and is primarily utilized to exclude other conditions, MRI is considered superior for identifying diaphragmatic, pleural, and hemorrhagic lesions. MRI demonstrates an overall sensitivity of 83% for diagnosing these abnormalities, making it the preferred imaging technique in such cases [ 20 ]. Diaphragmatic endometriosis often refers to endometriotic implants encountered on the visceral (abdominal) side of the diaphragm and it could be associated with thoracic endometriosis; [ 21 – 22 ] diaphragmatic endometriosis could cause symptoms like cyclic or noncyclic shoulder, arm, chest, or upper quadrant abdominal pain, but it is most frequently diagnosed incidentally during a laparoscopic surgery for a coexisting pelvic endometriosis. Abdominal wall endometriosis is divided into parietal and visceral endometriosis. Parietal endometriosis lesions involve primary lesions on abdominal wall (often iatrogenic, as for scar endometriosis after caesarean section or umbilical endometriosis after laparoscopic surgery) groin and perineum [ 23 – 24 ]. The frequency of abdominal wall endometriosis has been estimated to be 0.04%-5.5%, symptoms could include a palpable mass (99%), cyclic pain (71%) and cyclic bleeding [ 25 ] Umbilical endometriosis can be categorized into two types: secondary umbilical endometriosis, which is believed to arise from iatrogenic causes at the port site following laparoscopic surgery, and primary umbilical endometriosis, which occurs spontaneously without any history of surgical procedures [ 25 – 26 ]. Notably, primary umbilical endometriosis is more commonly observed compared to the secondary form. [ 27 ]. Inguinal endometriosis is a very unusual extrapelvic site for endometriosis. The estimated incidence is < 0.1% among those having endometriosis [ 28 ]. There is an increased right-sided predilection (~ 85% of reported cases) [ 29 ]. Inguinal endometriosis can present in various forms, such as cystic lesions within the hernia sac or the canal of Nuck, as well as solid masses located in the extra-pelvic round ligament or subcutaneous tissue. It predominantly affects the right groin, likely due to the theory of menstrual blood reflux into the pelvic cavity [ 30 ]. Clinically, it is identified by the presence of a groin mass, which may be associated with pain and periodic flare-ups or, alternatively, may be painless but accompanied by cyclical menstrual symptoms. 4.1 Case 1: Upper abdomen Diaphragm localization Clinical Case We present a case of a 36-year-old woman with known fibrotic pelvic endometriosis extended to the torus, uterosacral ligaments and round ligaments; intestinal adhesions were also present. With the intention of achieving pregnancy, the patient elected to terminate estrogen-progestin therapy. In the subsequent few mounts after interrupting estrogen-progestin therapy, the patient developed dysmenorrhea and pain projected on the right shoulder during the menstrual cycle. The physicians hypothesized a recurrence of the disease therefore they decide to perform an MRI exam extended also at the upper abdomen. The suspicion of diaphragmatic localization was accurate. Indeed, T1-weighted sequences revealed a focal hyperintensity in the right diaphragmatic pillar, adjacent to the seventh hepatic segment. This finding raised suspicion of a deep endometriotic nodule, measuring approximately 9x2mm (Fig. 1 ). A diagnosis of fibrotic deep endometriosis with associated extra pelvic endometriosis plaque in the active phase was made. Discussion Diaphragmatic endometriosis (DE) involving the full thickness of the diaphragm includes 1-1.5% of patients diagnosed with endometriosis [ 31 ]. The preoperative diagnosis of deep endometriosis (DE) poses challenges attributed to a significant proportion of asymptomatic patients, the limited sensitivity of existing imaging techniques, and a lack of suspicion among clinicians [ 21 ]. Remarkably, as many as 70% of individuals with DE exhibit no discernible symptoms [ 21 ]. This uncommon condition may remain asymptomatic and is occasionally discovered incidentally [ 31 ]. Diaphragmatic endometriosis, when symptomatic, typically presents with chest pain (often pleuritic and predominantly on the right side), dyspnea, epigastric discomfort, shoulder pain, and upper abdominal pain, which frequently occurs abruptly. The pain results from irritation of the sensory branches of the C3 and C5 nerve roots. Symptom severity depends on the depth and location of the lesions and is commonly linked to cyclical hormonal changes during the menstrual cycle. [ 31 – 32 ]. Diaphragmatic endometriosis predominantly affects the right side, with lesions commonly located in the anterior or posterior diaphragm and the area behind the liver. The higher prevalence in the subphrenic region is explained by the retrograde menstruation theory, suggesting that refluxed endometrial tissue becomes trapped by the falciform ligament near the right side of the diaphragm. MRI plays a crucial role in detecting these lesions, which are primarily visualized as hyperintense nodules on fat-suppressed T1-weighted sequences. According to Rousset et al., MRI offers a sensitivity of 78–83% for identifying these abnormalities [ 33 ]. The authors suggest that a report of lesions of extrapelvic endometriosis should be characterized and described like pelvic localizations. Extrapelvic endometriosis nodules can be defined based on shape and size: Foci: Thin and superficial, less than 1 cm Nodules Solid: tri-dimensional, more than 1 cm Plaques Fibrotic: bi-dimensional, more than 3 cm Superficial Isolated: lesions less than 5 mm, without infiltration of muscularis mucosa Another important parameter to evaluate is depth of invasion which divides deep endometriosis from simple: more than 5 mm with infiltration of muscularis or full thickness with total diaphragmatic infiltration [ 21 – 34 ]. Very often MRI alone is not able to provide all this information and staging remains surgical. The management of diaphragmatic or suspected thoracic endometriosis often relies on the patient’s medical history. For asymptomatic cases of diaphragmatic endometriosis, an expectant approach is strongly recommended as the most suitable treatment option compared to other interventions. [ 35 ] For symptomatic individuals, surgical intervention is considered effective, particularly when hormonal therapies have not provided relief [36 − 22]. The variables considered choosing the set therapy are patient age, future fertility desire, symptomatic status, disease extension and location. In literature Smith et al. suggest surgery in symptomatic and infertile patients with failure of medical treatment [ 21 ]. In our case, the patient had a “focus” of deep diaphragmatic endometriosis, however without full thickness infiltration of muscle. Our patient had minor symptoms with a low risk of developing complications, more over the plaque was single and small (1cm). Our patient underwent continuous hormonal progestin-based therapy, with consequent amenorrhea; at the clinical evaluation after six months, symptoms were improved. Dysmenorrhea was no more present because of the amenorrhea status and the irradiating pain to the shoulder almost completely disappeared. 4.2 Case 2: Posterior lateral compartment sciatic nerve localization Clinical Case We present a case of a 43-year-old woman, affected by deep infiltrating pelvic endometriosis (DIE), who had a known history of ovarian endometriosis and complained right sciatic pain, which was more evident during the menstrual cycle. She performed lumbo-sacral MRI which didn’t show significant alteration of rachis such as vertebral collapses or discal hernias. In relation to the catamenial progression of the symptoms the physician supposed an atypical localization of endometriosis, the patient underwent transvaginal ultrasound (TVUS) evaluation that showed bilateral endometriomas and a plaque of deep endometriosis in the posterior compartment. The lesions described at TVUS didn’t explain completely the symptoms, so she also underwent a pelvic MRI to better evaluate all pelvic compartment. The MRI examination recorded findings at the right ischial foramen, within the iliac obturator vascular-nervous bundle. It revealed a nodular region with spiculated margins measuring 25 mm in diameter, exhibiting non-homogeneous intensity. This variability was attributed to the presence of small hyperintense areas on T1-weighted imaging, indicative of hemorrhagic content (Fig. 2 ). This finding in the suspicion of active DIE plaque also appears to be related to the root of the ischial nerve. We conclude the MR report describing a condition of endometriosis affecting both intra-pelvic median and posterior compartment and extra-pelvic lateral compartment involving right sciatic nerve near the homolateral sciatic foramen. Our patient underwent surgical laparoscopic approach with the excision of the posterior DIE and nerve sparing surgery to remove the sciatic nodule; histological findings confirmed sciatic nerve endometriosis. The symptoms were resolved after surgical treatment and the patient started continuous progestin-based hormonal treatment to avoid disease relapse. Discussion The sciatic nerve, the largest somatic nerve in the human body, was first linked to cyclical sciatica in a case reported by Head et al. in 1962 [ 37 ]. The exact mechanism behind the sciatic localization of endometrial cells remains unclear. One theory suggests migration of endometrial cells from pelvic endometriotic lesions, while other hypotheses propose mechanisms such as hematogenous spread, coelomic metaplasia, or embryonic cell remnants [ 37 – 39 ]. Additionally, Possover et al. introduced a "neurologic hypothesis" in 2007, describing a case of isolated sciatic nerve endometriosis with no detectable pelvic endometriotic lesions [ 40 ]. The most frequent site of sciatic nerve involvement in endometriosis is near the greater sciatic foramen, with the right sciatic nerve being more commonly affected than the left. [ 41 ]. Cyclical bleeding into adjacent tissues leads to inflammation, fibrosis and scarring, which exacerbate nerve compression over time. The diagnosis of sciatic nerve endometriosis is based on clinical symptoms and imaging studies, with histopathological examination providing definitive confirmation. Key clinical indicators include sciatica that follows a cyclical pattern related to menstruation. As the condition progresses, pain-free intervals shorten, and the pain becomes persistent, though it continues to worsen during menstruation. MRI is the preferred imaging modality for detecting sciatic endometriosis, offering a sensitivity of 90% and a specificity of 98% [ 42 ]. The appearance of endometriotic lesions varies with the stage of hemorrhage, typically showing high signal intensity on T1-weighted images and a combination of high and low signal intensities on T2-weighted images. Importantly, the absence of pelvic endometriosis does not rule out sciatic nerve involvement [ 43 ]. Surgical treatment depends on the extent of the disease. If only the pelvic portion of the sciatic nerve is affected, a skilled gynecologist can perform a laparoscopic or robotic procedure [ 44 ]. when the extra-pelvic portion or both pelvic and extra-pelvic parts of the nerve are involved, a trans-gluteal surgical approach is required. In such cases, a multidisciplinary team comprising neurosurgeons and orthopedic specialists is essential. [ 45 ]. In conclusion, sciatic nerve endometriosis should be considered in patients presenting with sciatica exhibiting a cyclical pattern. MRI serves as the optimal imaging modality to support the clinical diagnosis. Treatment requires the involvement of a multidisciplinary surgical team with a thorough understanding of retroperitoneal neuroanatomy. The choice of surgical approach, whether laparoscopic or trans-gluteal, should be carefully planned prior to the procedure. Early diagnosis, timely intervention, and comprehensive post-operative physiotherapy can significantly enhance recovery outcomes for these patients. 4.3 Case 3: Anterior lateral compartment abdominal wall and inguinal endometriosis Clinical Case A 44-year-old patient presented with heavy menstrual periods. The patient had experienced two spontaneous pregnancies and deliveries and presented with a current medical history of systemic lupus erythematosus under treatment. At the first clinical evaluation she complained of dysmenorrhea (Visual Assessment Score, VAS 9), dyspareunia (VAS 7), with no dyschezia or dysuria. She also complained of severe pain (VAS 10) in the right inguinal region, during menstrual phase. She had never taken hormonal treatments. Because of these invalidating symptoms she underwent transvaginal ultrasound evaluation (TVS) which showed a globose uterus presenting fibromatosis and direct signs of adenomyosis; a hypoechoic nodule of 10x9x4 mm in size at the level of the torus uteri and an analogous nodule of 15x8x9 mm in size in the posterior vaginal fornix were detected. Ovaries were regular. In the right inguinal region, a painful hypoechoic nodule of 39x14 mm in size, with irregular margins, moderately vascularized at color-Doppler US, was observed. All these findings led to the suspicion of pelvic DIE. The probability of an extrapelvic endometriosis, as inguinal endometriosis localization, was high and an indication to carry out an MR exam was given. She was referred to dedicated radiologist to perform MR. The MR exam was performed with T1 fat saturation and T2 sequences in axial, coronal and sagittal planes without contrast medium agent (Fig. 3 ). MRI showed an ovoid mass localized in the anterior abdominal wall which infiltrated the edge of the rectus abdominis muscle and extended to the wall of right inguinal canal with probable involvement of the pubic nerve as hypothesized from clinical symptoms. The MR images, according with US, were compatible with a localization of endometrial glands as a glandular-cystic plaque, due to typical MRI features. Contrast medium agent was not used. Based on the absence of previous surgery, clinical symptoms, US and MRI features, our diagnostic hypothesis was endometriosis of the canal of Nuck (Fig. 4 ). After diagnosis, the patient started a continuous progestin-based hormonal treatment for 12 months, inducing amenorrhea, with improvement of dysmenorrhea but with persistence of dyspareunia and inguinal pain. Due to the persistence of symptoms the patient underwent laparoscopy to remove DIE and groin incision to remove inguinal endometriosis. At the follow-up evaluation symptoms were reduced (dysmenorrhea VAS 5, dyspareunia VAS 4, and absent inguinal pain). Discussion Endometriosis of the inguinal region may involve inguinal hernia sac, canal of Nuck, uterine round ligament (RLUs) and subcutaneous tissue [ 46 – 47 ]. Inguinal endometriosis (from the labia majora to the abdominal wall) is a very unusual extrapelvic site for endometriosis, with incidence < 0.1% [ 48 ]. Incomplete obliteration of the canal of Nuck is known as a patent processus vaginalis and can result in either an inguinal hernia or a hydrocele in female children. It can provide a pathway for superficial inguinal endometriosis [ 49 ]. RLUs have an intrapelvic and an extrapelvic portion where the extrapelvic one is the distal part of the ligament in the canal of Nuck [ 2 ]. Endometriosis from RLUs may advance through the inguinal ring into the inguinal canal, and this may be an anatomical pathway for endometrial implants to the superficial inguinal soft tissues [ 50 ]. Symptoms of endometriosis of the intrapelvic portion of the RLUs are nonspecific, usually referred as pain localized in the lower abdomen [ 2 ]. Our patient had severe groin pain during menstrual cycle, associated with superficial swelling at the right inguinal level. On sonographic imaging our patient had a solid (hypoechoic) nodule, with irregular margins, moderately vascularized on color doppler. Nevertheless, the sonographic appearance of inguinal endometriosis is not typical, varying between a predominantly solid, a cystic or combined mass [ 50 ]. When extra-pelvic endometriosis is suspected the integration of US and MRI, like in our case, is the best approach in the diagnostic workup [ 2 ],[ 5 ], [ 50 ]. Differential diagnosis includes abdominal wall masses, such as hernias, lipomas, sebaceous cysts hematomas, and malignant tumors [ 51 ]. Our patients underwent first line medical treatment and subsequently surgery. As suggested by Delkalitsis et al, while other treatment modalities like hormonal suppressive therapy remain to be evaluated, surgical treatment consists of excision of the mass from the canal of Nuck and subcutaneous lesions is the better choice in case of severe symptoms [ 50 ]. 4. Conclusion The diagnostic role of MR in endometriosis is evolving, necessitating radiologists to possess a meaningful understanding of the several clinical and imaging manifestations associated with both typical and atypical localizations. This becomes particularly crucial when assessing patients with clinical suspicion of DIE. Radiologists must diligently explore, document, and stratify the disease across a spectrum of locations in endometriosis patients. Accurate diagnosis holds paramount significance for steering appropriate patient management. While laparoscopy remains the benchmark for endometriosis diagnosis, certain diagnostic challenges exist, such as the potential oversight of nodules concealed by adhesions and subperitoneal disease. Successful treatment strategies encompass hormonal-based therapies including combined oral contraceptives (COC), progesterone agents, alongside lesion removal with radical surgery. In instances where surgery is indicated, MRI serves as a valuable tool, providing a comprehensive roadmap. This facilitates effective presurgical counseling and empowers the surgeon in the meticulous eradication of all endometriotic implants. The integration of MRI into the diagnostic and therapeutic framework enhances precision and contributes significantly to the overall management of endometriosis. Declarations Informed consent The patient(s), or their next of kin, or their legal representative(s) signed: - written informed consent for the performance of contrast-enhanced MRI. - written informed consent to the use of images for research purposes and scientific description (attached below). The privacy of the patient has been assured in all materials. Written informed consent forms from the patient(s) and/or their legal representative(s)/guardian(s) are preserved in our department archive (U.O.C. Diagnostic Imaging, PTV Policlinico “Tor Vergata” University, Viale Oxford 81, 00133, Rome, Italy) Ethics The need for ethical approval was waived off by the ethical committee “CET Lazio Area 2” of Roma Tor Vergata University because our study is a case series, and we iconographically describe images acquired during routine MRI examinations. As the study relies on standard clinical practice, it does not require approval from the ethics committee. Author Contribution All authors contributed equally to the work. The tasks were divided as follows:F.R, F.M and C.R wrote the main manuscript text under the supervision of R.M and V.F, radiologists with over 10 years of experience in diagnostic imaging of the female pelvis.C.P.R. Conducted multiple ongoing reviews of the manuscript with particular attention to scientific terminology and English language.M.L prepared figures 1-4 and Article layoutF.G and G.M conducted the final review Data Availability As per the Ministerial Decree of February 14, 1997, all MRI images of the reported cases will be stored in the digital archive of our polyclinic for 10 years.The clinical data collected will be gathered by the Research Center and processed there. The Data Protection Officer for the healthcare company can be contacted upon reasonable request.The informed consents will be archived in the archive of our polyclinic as per Law No. 219 of December 22, 2017 References Feldman MK, VanBuren WM, Barnard H, Taffel MT, Kho RM. Systematic interpretation and structured reporting for pelvic magnetic resonance imaging studies in patients with endometriosis: value added for improved patient care. Abdom Radiol (NY). 2020;45(6):1608–1622. doi: 10.1007/s00261-019-02182-1 . 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Diagnosis and Treatment of Catamenial Pneumothorax: A Systematic Review. J. Minim. Invasive Gynecol. 2020, 27, 48–53. Andres MP, Arcoverde FVL, Souza CCC, Fernandes LFC, Abrão MS, Kho RM. Extrapelvic Endometriosis: A Systematic Review. J Minim Invasive Gynecol. 2020;27(2):373–389. Emre A, Akbulut S, Yilmaz M, Bozdag Z. Laparoscopic trocar port site endometriosis: a case report and brief literature review. Int Surg. 2012;97(2):135–139 Hirata T, Koga K, Osuga Y. Extra-pelvic endometriosis: A review. Reprod Med Biol. 2020;19(4):323–333. doi: 10.1002/rmb2.12340 . PMID: 33071634; PMCID: PMC7542014. Horton JD, DeZee KJ, Ahnfeldt EP, Wagner M. Abdominal wall endometriosis: a surgeon's perspective and review of 445 cases. Am J Surg. 2008;196(2):207–212. Hirata T, Koga K, Kitade M, et al. A national survey of umbilical endometriosis in Japan. J Minim Invasive Gynecol. 2020;27(1):80–87. Sun Z, Zhu L, Lang J. A Rare Extrapelvic Endometriosis: Inguinal Endometriosis. J Reprod Med. 2010;55(1–2):62–6. Yang D, Kim H, Ryu J, Lim J, Kim G. Sonographic Findings of Inguinal Endometriosis. J Ultrasound Med. 2010;29(1):105–10. doi: 10.7863/jum.2010.29.1.105 Li SH, Sun HZ, Li WH, Wang SZ. Inguinal endometriosis: Ten case reports and review of literature. World J Clin Cases. 2021;9(36):11406–11418. doi: 10.12998/wjcc.v9.i36.11406 . PMID: 35071572; PMCID: PMC8717526. Kaveh M, Tahermanesh K, Mehdizadeh Kashi A, Tajbakhsh B, Mansouri GH, Sadegi K. Endometriosis of Diaphragm: A Case Report. Int J Fertil Steril. 2018;12(3):263–266. doi: 10.22074/ijfs.2018.5379 . Epub 2018 Jun 20. PMID: 29935074; PMCID: PMC6018178. Basama F. Widespread intraperitoneal and diaphragmatic endometriosis presenting with frequent bowel motions and chronic shoulder tip pain. Journal of Obstetrics and Gynaecology 24:931–932 Rousset P, Gregory J, Rousset-Jablonski C, Hugon-Rodin J, Regnard JF, Chapron C, Coste J, Golfier F, Revel MP. MR diagnosis of diaphragmatic endometriosis. Eur Radiol. 2016;26(11):3968–3977. doi: 10.1007/s00330-016-4226-5. Epub 2016 Feb 12. PMID: 26868500. Ceccaroni M, Roviglione G, Giampaolino P, Clarizia R, Bruni F, Ruffo G, et al. 2013. Laparoscopic surgical treatment of diaphragmatic endometriosis: a 7-year single-institution retrospective review. Surgical Endoscopy 27:625–632 Falcone T, Lebovic DI. Clinical management of endometriosis. Obstet Gynecol. 2011; 118(3): 691–705. Nezhat C, Seidman DS, Nezhat F, Nezhat C. Laparoscopic surgical management of diaphragmatic endometriosis. Fertil Steril. 1998; 69(6): 1048–1055 Head W.B., Welch J.S., Mussey E., Espinosa R.E. Cyclic sciatica: report of a case with introduction of a new surgical sign. JAMA. 1962;180:521–524. Dhote R., Tudoret L., Bachmeyer C., Lagmann P., Christoforov B. Cyclic sciatica: a manifestation of compression of the sciatic nerve by endometriosis: a case report. Spine. 1996;21:2277–2279. Vercellini P., Chapron C., Fedele L., Frontino G., Zaina B., Crosignani P.G. Evidence for asymmetric distribution of sciatic nerve endometriosis. Obstet. Gynecol. 2003;102(2):383–387. doi: 10.1016/s0029-7844(03)00532-5 . (PMID: 12907116) Possover M., Chiantera V. Isolated infiltrative endometriosis of the sciatic nerve: a report of three patients. Fertil. Steril. 2007;87(417):e17–e19. Possover M. Five-year follow-up after laparoscopic large nerve resection for deep infiltrating sciatic nerve endometriosis. J. Minim. Invasive Gynecol. 2017;24:822–826. Gaeta M., Minutoli F., Mileto A., et al. Nuck canal endometriosis: MR imaging findings and clinical features. Abdom. Imaging. 2010;35:737–741. Saar T.D., Pacquée S., Conrad D.H., Sarofim M., De Rosnay P., Rosen D., Cario G., Chou D. Endometriosis involving the sciatic nerve: a case report of isolated endometriosis of the sciatic nerve and review of the literature. Gynecol. Minim. Invas. Ther. 2018;7(2):81 Roman H., Seyer-Hansen M., Dennis T., Merlot B. Excision of deep endometriosis nodules of the sciatic nerve in 10 steps. J. Minim. Invasive Gynecol. 2021;28(10):1685–1686. doi: 10.1016/j.jmig.2021.05.019 . Epub 2021 Jun 4. PMID: 34091045. Yanchun L., Yunhe Z., Meng X., Shuqin C., Qingtang Z., Shuzhong Y. Removal of an endometrioma passing through the left greater sciatic foramen using a concomitant laparoscopic and transgluteal approach: case report. BMC Womens Health. 2019;19(1):95. doi: 10.1186/s12905-019-0796-0 . PMID: 31299947; PMCID: PMC6624926. Prodromidou A, Pandraklakis A, Rodolakis A, Thomakos N. Endometriosis of the Canal of Nuck: A Systematic Review of the Literature. Diagnostics (Basel). 2020;11(1):3. doi: 10.3390/diagnostics11010003 . PMID: 33375037; PMCID: PMC7821999. Kiyak G., Ergul E., Sarıkaya S., Yazgan A. Endometriosis of the groin hernia sac: Report of a case and review of the literature. Hernia J. Hernias Abdom. Wall Surg. 2010;14:215–217. doi: 10.1007/s10029-009-0532-z . Sun Z, Zhu L, Lang J. A Rare Extrapelvic Endometriosis: Inguinal Endometriosis. J Reprod Med. 2010;55(1–2):62–6. Gaillard F, Sheikh Y, Elfeky M, et al. Canal of Nuck. Reference article, Radiopaedia.org (Accessed on 23 Mar 2024) https://doi.org/10.53347/rID-11091 Dalkalitsis A, Salta S, Tsakiridis I, Dagklis T, Kalogiannidis I, Mamopoulos A, Daniilidis A, Athanasiadis A, Navrozoglou I, Paschopoulos M, Vatopoulou A, Kosmas I. Inguinal endometriosis: A systematic review. Taiwan J Obstet Gynecol. 2022;61(1):24–33. doi: 10.1016/j.tjog.2021.11.007. PMID: 35181041 Gui B, Valentini AL, Ninivaggi V, Miccò M, Zecchi V, Grimaldi PP, Cambi F, Guido M, Bonomo L. Shining light in a dark landscape: MRI evaluation of unusual localization of endometriosis. Diagn Interv Radiol. 2017 Jul-Aug;23(4):272–281. doi: 10.5152/dir.2017.16364 . PMID: 28703103; PMCID: PMC5508950. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 10 Mar, 2025 Reviews received at journal 05 Feb, 2025 Reviewers agreed at journal 03 Feb, 2025 Reviews received at journal 26 Jan, 2025 Reviewers agreed at journal 14 Jan, 2025 Reviewers agreed at journal 14 Jan, 2025 Reviews received at journal 09 Jan, 2025 Reviewers agreed at journal 08 Jan, 2025 Reviewers invited by journal 08 Jan, 2025 Editor assigned by journal 01 Jan, 2025 Submission checks completed at journal 31 Dec, 2024 First submitted to journal 06 Dec, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5595138","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Case Report","associatedPublications":[],"authors":[{"id":396323504,"identity":"241ae7d1-809f-4b64-8cf6-593c3b204476","order_by":0,"name":"Rosaria Meucci","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Rosaria","middleName":"","lastName":"Meucci","suffix":""},{"id":396323506,"identity":"9d584ae4-08bf-475d-8c96-f2c4a91f6e8f","order_by":1,"name":"Francesco Garaci","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Francesco","middleName":"","lastName":"Garaci","suffix":""},{"id":396323507,"identity":"2aae44da-23bf-489d-b7dd-f23e92218235","order_by":2,"name":"Valeria Fiaschetti","email":"data:image/png;base64,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","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":true,"prefix":"","firstName":"Valeria","middleName":"","lastName":"Fiaschetti","suffix":""},{"id":396323509,"identity":"8494e16c-6a2b-4b20-9496-75ce86e310c3","order_by":3,"name":"Francesca Montesanto","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Francesca","middleName":"","lastName":"Montesanto","suffix":""},{"id":396323510,"identity":"69e77c76-d4e5-4324-9fa5-000f99324eab","order_by":4,"name":"Flavia Rufi","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Flavia","middleName":"","lastName":"Rufi","suffix":""},{"id":396323511,"identity":"45fb1d97-7dd9-4037-abcd-1cf3b1628cd6","order_by":5,"name":"Mario Laudazi","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Mario","middleName":"","lastName":"Laudazi","suffix":""},{"id":396323512,"identity":"386872ad-ecf7-40eb-8d3f-cccfff4c5654","order_by":6,"name":"Colleen Patricia Ryan","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Colleen","middleName":"Patricia","lastName":"Ryan","suffix":""},{"id":396323516,"identity":"48c688be-fef0-4f90-9510-298d5befa322","order_by":7,"name":"Consuelo Russo","email":"","orcid":"","institution":"Agostino Gemelli University Polyclinic","correspondingAuthor":false,"prefix":"","firstName":"Consuelo","middleName":"","lastName":"Russo","suffix":""},{"id":396323517,"identity":"224643af-fdc6-41dc-a21c-acca8ba69599","order_by":8,"name":"Guglielmo Manenti","email":"","orcid":"","institution":"University of Rome Tor Vergata","correspondingAuthor":false,"prefix":"","firstName":"Guglielmo","middleName":"","lastName":"Manenti","suffix":""}],"badges":[],"createdAt":"2024-12-06 16:38:36","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5595138/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5595138/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":72796497,"identity":"e96707ee-08f0-453c-82eb-c9243983b033","added_by":"auto","created_at":"2025-01-02 09:03:34","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":273442,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eDiaphragm localization\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea-b: T1FS sequences coronal and axial plane of upper abdomen shows hyperintense linear area at the level of the right diaphragmatic pillar (dtm approximately 9mm); alteration compatible with active haemorrhagic endometriotic plaque.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-5595138/v1/05451230140e8106e9262d19.png"},{"id":72796498,"identity":"54aed3c2-3100-4956-b67c-211d2aaecacd","added_by":"auto","created_at":"2025-01-02 09:03:34","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":944083,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eSciatic nerve localization\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea-b\u003c/em\u003e\u003cem\u003e\u003cstrong\u003e:\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e axial T1FSw and T2w sequences, c: coronal T2w sequences.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMR images show an endometriosis plaque infiltrating ischiatic nerve, hyperintense on T1w sequences, compatible with an active localization of extra-pelvic endometriosis in pelvic posterior lateral compartment.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-5595138/v1/bf4652e45b2b3f06ed93974e.png"},{"id":72798613,"identity":"253d340f-5c84-41ac-bccf-7670dbbed946","added_by":"auto","created_at":"2025-01-02 09:11:35","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":744009,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eAbdominal wall localization\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea-b: T1FS- and T2FS -weighted axial sequences; c-d: T1FS- and T2-weighted sagittal sequences. MR images show an ovoid mass localized in the abdominis wall region which infiltrate the edge of the abdominis rectus muscle and the anterior wall of inguinal canal\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eOn T1-weighted sequence the lesion is isointense to the muscle.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eOn T2-weighted sequence the lesion shows a mixed hypointense and hyperintense cyst detectable to endometrial glands.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-5595138/v1/6dbe88196ad629ed448f5623.png"},{"id":72798614,"identity":"3c0fffb5-b9a6-4094-a809-be0de325dca2","added_by":"auto","created_at":"2025-01-02 09:11:35","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":670026,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003ecanal of Nuck localization\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ea-b: T2-weighted axial and sagittal sequences. MR images show the same lesion as figure 3 closely adherent to the right inguinal region suspicious for canal of Nuck endometriosis.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-5595138/v1/2511a9782893db65e44a490c.png"},{"id":72798930,"identity":"89d647e0-aacf-4a35-a5b7-5d07d3bc485f","added_by":"auto","created_at":"2025-01-02 09:19:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4647557,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5595138/v1/a770c40f-3f23-4840-b77c-6dc66fe9923f.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eExtragenital and Extrapelvic Endometriosis: Literature Update and Mri Immaging Case Collection of Unusual Localizations\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eEndometriosis is a prevalent gynecologic pathology estimated to affect 10% of women [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] and is defined by the ectopic presence of endometrial tissue outside the uterine cavity with consequent recurrent intralesional bleeding and resulting fibrosis. Feldman et al. discerned three forms of pelvic endometriosis: (a) superficial peritoneal lesions; (b) ovarian endometrioma; (c) deep (or solid infiltrating) endometriosis (\\), histologically identified as a lesion that extends more than 5 mm into the sub peritoneal space or involving the walls of pelvic organs and ligaments [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Preeminent sites for endometriotic lesions include the ovaries, pelvic peritoneum, uterosacral ligaments, and torus uterine [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Atypical pelvic endometriosis localizations can occur in the cervix, vagina, round ligaments, ureter, and nerves. Moreover, rare extra pelvic endometriosis implants can be localized in the upper abdomen, subphrenic fold or in the abdominal wall. While characteristic symptoms comprise secondary dysmenorrhea and cyclic or persistent pelvic pain, the diagnostic context is often non-specific, contributing to a notable diagnostic delay of up to 10 years [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Unusual sites of endometriosis may be associated with specific symptoms depending on different localizations [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eExtra pelvic compartments include right bowel structures (cecum, ileum, and appendix), sigmoid colon, lumbopelvic ureter, abdominal wall as well as umbilicus, and external part of inguinal canal [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], diaphragm and this paper explores three rare endometriosis localizations, highlighting their Magnetic Resonance Imaging (MRI) and clinical features in cases involving the sciatic nerve, diaphragm and abdominal wall.\u003c/p\u003e"},{"header":"2. Endometriosis non-invasive diagnosis","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 role of MRI and MRI features\u003c/h2\u003e \u003cp\u003eMRI is a useful noninvasive tool used to diagnose endometriosis because of the absence of ionizing radiation, multiplanar projections, and high contrast resolution with high sensitivity for detection of hemorrhagic lesions [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAccording to the guidelines established by the European Society of Urogenital Radiology (ESUR), the paramount indication for MRI lies in the examination of deep endometriosis. ESUR further advocates for MRI utilization in cases marked by positive clinical features but negative ultrasonography (US) results, as well as in presurgical planning and as a second-line test when US proves inconclusive [\u003cspan additionalcitationids=\"CR3 CR4 CR5 CR6\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eNowadays, imaging techniques, including MRI and transvaginal ultrasound, have reached high diagnostic accuracy in detecting endometriosis; several papers demonstrated high agreement between imaging and surgical findings [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This is also mentioned in the recent ESHRE guidelines [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], which highlight that surgery is no longer the gold standard method to diagnose endometriosis and imaging can be used for the diagnosis and for the consequent management of patients without the need for diagnostic surgery.\u003c/p\u003e \u003cp\u003eThe SEF (Stiftung Endometriose-Forschung; Scientific Endometriosis Foundation) published in the 2003 and 2005 the ENZIAN classification, which established a useful tool for DIE classification focused also on MRI [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The latest revision of the ENZIAN score 2020 proposes a new comprehensive classification system, which includes the anatomical location and the size of the different forms of endometriotic lesions, the presence of adhesions, and the degree of involvement of the adjacent organs [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRecent ESUR guidelines do not provide specific recommendations regarding the timing of MRI in relation to the menstrual cycle [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRegarding technical recommendations, the application of fat saturation is advised for enhanced precision. Chemical frequency-selective fat saturation, targeting the high signal intensity inherent to fat tissue, proves instrumental in accentuating distinctions among non-fat T1-weighted hyperintense structures, thereby amplifying the visibility of minute hemorrhagic lesions associated with endometriosis [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn MRI, deep pelvic endometriosis manifests as hemorrhagic cysts or plaques, exhibiting hyperintensity in T1-weighted sequences, as well as solid or fibrous lesions characterized by low signal intensity on both T1- and T2-weighted images, indicative of an infiltrating behavior. High-resolution T1 and T2-weighted images are employed for meticulous evaluation, particularly when lesions involve ligaments and the subperitoneal space (\u0026gt;\u0026thinsp;5mm under peritoneal sierosa). Discrimination between endometriotic tissue with hemorrhagic content and fibrosis is achievable through MRI [\u003cspan additionalcitationids=\"CR4 CR5 CR6 CR7 CR8 CR9 CR10 CR11 CR12\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn advanced stages, endometriosis is often associated with adhesions, appearing as spiculated bands of low to intermediate signal intensity on T1- and T2-weighted imaging. These adhesions can obscure the interfaces between organs, leading to atypical imaging characteristics such as peritoneal space obliteration, fixed fluid accumulations, and distortion or displacement of nearby organs. To enhance visualization, axial, coronal, and sagittal planes are typically used, with oblique planes aligned to the affected organs providing additional information. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn conclusion, MRI is essential to giving an exhaustive DIE roadmap, necessary in preoperative decision making, particularly in cases of extra pelvic disease where transvaginal US (first line imaging) also performed by expert operators is not accurate [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 MRI acquisition protocol\u003c/h2\u003e \u003cp\u003eAs described above endometriosis is a multifocal and systemic disease and MRI allows complete evaluation of every abdominal compartment, identifying and mapping all types of endometriosis lesions within a single study [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAt our institution, MRI were acquired with high field-strength (3 Tesla) systems, acquisition of axial, coronal and sagittal T2-weighted images and spin-echo or gradient-echo axial T1-weighted images obtained with or without fat suppression, with a slice thickness of 3 mm. In addition, in selected and atypical cases, axial T1-weighted images were obtained after intravenous administration of a gadolinium-based contrast agent. The usefulness of intravenous gadolinium injection to characterize endometriosis is still under discussion. Incidentally, international recommendations assert that the utilization of contrast agents typically does not contribute substantially to the initial diagnostic information [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In our hospital, we administer contrast medium agents solely when deemed beneficial for diagnosis. Nevertheless, it is deemed mandatory in cases where malignant transformation of endometrioma is suspected, as highlighted by Schneider at al. [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. MRI with vaginal opacification using sonographic gel is recognized as a viable option for evaluating deep pelvic endometriosis. Some papers recommended MRI with gel opacification of vagina for studying usual localization of deep infiltrating endometriosis, particularly for the added value in evaluation of recto-vaginal septum, utero-sacral ligaments and posterior vaginal fornix. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. It's important to note that in our recent practice, we refrain from the practice of distending the vagina with sonographic gel [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Unusual localization of extragenital endometriosis and case reports","content":"\u003cp\u003e \u003cb\u003eRenal endometriosis\u003c/b\u003e occurs in approximately less than 1% of all cases. Flank pain, haematuria and renal mass are the most common presentations of renal endometriosis, and it is sometimes misdiagnosed as renal cell carcinoma on imaging [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn case of symptoms, MRI is mandatory, to clarify the extent of the lesion and the depth of lesion invasion and to plan adequate surgical treatment [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePatients with \u003cb\u003ethoracic endometriosis\u003c/b\u003e (TE) usually present with the triad of pain, pneumothorax and haemoptysis [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eCT and MRI are the primary imaging modalities used for TE. While CT lacks specificity for TE and is primarily utilized to exclude other conditions, MRI is considered superior for identifying diaphragmatic, pleural, and hemorrhagic lesions. MRI demonstrates an overall sensitivity of 83% for diagnosing these abnormalities, making it the preferred imaging technique in such cases [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cb\u003eDiaphragmatic endometriosis\u003c/b\u003e often refers to endometriotic implants encountered on the visceral (abdominal) side of the diaphragm and it could be associated with thoracic endometriosis; [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] diaphragmatic endometriosis could cause symptoms like cyclic or noncyclic shoulder, arm, chest, or upper quadrant abdominal pain, but it is most frequently diagnosed incidentally during a laparoscopic surgery for a coexisting pelvic endometriosis.\u003c/p\u003e \u003cp\u003e \u003cb\u003eAbdominal wall endometriosis\u003c/b\u003e is divided into parietal and visceral endometriosis. Parietal endometriosis lesions involve primary lesions on abdominal wall (often iatrogenic, as for scar endometriosis after caesarean section or umbilical endometriosis after laparoscopic surgery) groin and perineum [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe frequency of abdominal wall endometriosis has been estimated to be 0.04%-5.5%, symptoms could include a palpable mass (99%), cyclic pain (71%) and cyclic bleeding [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eUmbilical endometriosis can be categorized into two types: secondary umbilical endometriosis, which is believed to arise from iatrogenic causes at the port site following laparoscopic surgery, and primary umbilical endometriosis, which occurs spontaneously without any history of surgical procedures [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Notably, primary umbilical endometriosis is more commonly observed compared to the secondary form. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInguinal endometriosis is a very unusual extrapelvic site for endometriosis. The estimated incidence is \u0026lt;\u0026thinsp;0.1% among those having endometriosis [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. There is an increased right-sided predilection (~\u0026thinsp;85% of reported cases) [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInguinal endometriosis can present in various forms, such as cystic lesions within the hernia sac or the canal of Nuck, as well as solid masses located in the extra-pelvic round ligament or subcutaneous tissue. It predominantly affects the right groin, likely due to the theory of menstrual blood reflux into the pelvic cavity [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Clinically, it is identified by the presence of a groin mass, which may be associated with pain and periodic flare-ups or, alternatively, may be painless but accompanied by cyclical menstrual symptoms.\u003c/p\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Case 1: Upper abdomen Diaphragm localization\u003c/h2\u003e \u003cp\u003e \u003cem\u003eClinical Case\u003c/em\u003e \u003c/p\u003e \u003cp\u003eWe present a case of a 36-year-old woman with known fibrotic pelvic endometriosis extended to the torus, uterosacral ligaments and round ligaments; intestinal adhesions were also present.\u003c/p\u003e \u003cp\u003eWith the intention of achieving pregnancy, the patient elected to terminate estrogen-progestin therapy. In the subsequent few mounts after interrupting estrogen-progestin therapy, the patient developed dysmenorrhea and pain projected on the right shoulder during the menstrual cycle. The physicians hypothesized a recurrence of the disease therefore they decide to perform an MRI exam extended also at the upper abdomen. The suspicion of diaphragmatic localization was accurate. Indeed, T1-weighted sequences revealed a focal hyperintensity in the right diaphragmatic pillar, adjacent to the seventh hepatic segment. This finding raised suspicion of a deep endometriotic nodule, measuring approximately 9x2mm (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A diagnosis of fibrotic deep endometriosis with associated extra pelvic endometriosis plaque in the active phase was made.\u003c/p\u003e \u003cp\u003e \u003cem\u003eDiscussion\u003c/em\u003e \u003c/p\u003e \u003cp\u003eDiaphragmatic endometriosis (DE) involving the full thickness of the diaphragm includes 1-1.5% of patients diagnosed with endometriosis [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The preoperative diagnosis of deep endometriosis (DE) poses challenges attributed to a significant proportion of asymptomatic patients, the limited sensitivity of existing imaging techniques, and a lack of suspicion among clinicians [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Remarkably, as many as 70% of individuals with DE exhibit no discernible symptoms [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. This uncommon condition may remain asymptomatic and is occasionally discovered incidentally [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDiaphragmatic endometriosis, when symptomatic, typically presents with chest pain (often pleuritic and predominantly on the right side), dyspnea, epigastric discomfort, shoulder pain, and upper abdominal pain, which frequently occurs abruptly. The pain results from irritation of the sensory branches of the C3 and C5 nerve roots. Symptom severity depends on the depth and location of the lesions and is commonly linked to cyclical hormonal changes during the menstrual cycle. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDiaphragmatic endometriosis predominantly affects the right side, with lesions commonly located in the anterior or posterior diaphragm and the area behind the liver. The higher prevalence in the subphrenic region is explained by the retrograde menstruation theory, suggesting that refluxed endometrial tissue becomes trapped by the falciform ligament near the right side of the diaphragm. MRI plays a crucial role in detecting these lesions, which are primarily visualized as hyperintense nodules on fat-suppressed T1-weighted sequences. According to Rousset et al., MRI offers a sensitivity of 78\u0026ndash;83% for identifying these abnormalities [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe authors suggest that a report of lesions of extrapelvic endometriosis should be characterized and described like pelvic localizations. Extrapelvic endometriosis nodules can be defined based on shape and size:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eFoci: Thin and superficial, less than 1 cm\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNodules Solid: tri-dimensional, more than 1 cm\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003ePlaques Fibrotic: bi-dimensional, more than 3 cm\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSuperficial Isolated: lesions less than 5 mm, without infiltration of muscularis mucosa\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eAnother important parameter to evaluate is depth of invasion which divides deep endometriosis from simple: more than 5 mm with infiltration of muscularis or full thickness with total diaphragmatic infiltration [\u003cspan additionalcitationids=\"CR22 CR23 CR24 CR25 CR26 CR27 CR28 CR29 CR30 CR31 CR32 CR33\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Very often MRI alone is not able to provide all this information and staging remains surgical.\u003c/p\u003e \u003cp\u003eThe management of diaphragmatic or suspected thoracic endometriosis often relies on the patient\u0026rsquo;s medical history. For asymptomatic cases of diaphragmatic endometriosis, an expectant approach is strongly recommended as the most suitable treatment option compared to other interventions. [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] For symptomatic individuals, surgical intervention is considered effective, particularly when hormonal therapies have not provided relief [36\u0026thinsp;\u0026minus;\u0026thinsp;22].\u003c/p\u003e \u003cp\u003eThe variables considered choosing the set therapy are patient age, future fertility desire, symptomatic status, disease extension and location. In literature Smith et al. suggest surgery in symptomatic and infertile patients with failure of medical treatment [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn our case, the patient had a \u0026ldquo;focus\u0026rdquo; of deep diaphragmatic endometriosis, however without full thickness infiltration of muscle. Our patient had minor symptoms with a low risk of developing complications, more over the plaque was single and small (1cm). Our patient underwent continuous hormonal progestin-based therapy, with consequent amenorrhea; at the clinical evaluation after six months, symptoms were improved. Dysmenorrhea was no more present because of the amenorrhea status and the irradiating pain to the shoulder almost completely disappeared.\u003c/p\u003e\u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Case 2: Posterior lateral compartment sciatic nerve localization\u003c/h2\u003e \u003cp\u003e \u003cem\u003eClinical Case\u003c/em\u003e \u003c/p\u003e \u003cp\u003eWe present a case of a 43-year-old woman, affected by deep infiltrating pelvic endometriosis (DIE), who had a known history of ovarian endometriosis and complained right sciatic pain, which was more evident during the menstrual cycle.\u003c/p\u003e \u003cp\u003eShe performed lumbo-sacral MRI which didn\u0026rsquo;t show significant alteration of rachis such as vertebral collapses or discal hernias.\u003c/p\u003e \u003cp\u003eIn relation to the catamenial progression of the symptoms the physician supposed an atypical localization of endometriosis, the patient underwent transvaginal ultrasound (TVUS) evaluation that showed bilateral endometriomas and a plaque of deep endometriosis in the posterior compartment. The lesions described at TVUS didn\u0026rsquo;t explain completely the symptoms, so she also underwent a pelvic MRI to better evaluate all pelvic compartment.\u003c/p\u003e \u003cp\u003eThe MRI examination recorded findings at the right ischial foramen, within the iliac obturator vascular-nervous bundle. It revealed a nodular region with spiculated margins measuring 25 mm in diameter, exhibiting non-homogeneous intensity. This variability was attributed to the presence of small hyperintense areas on T1-weighted imaging, indicative of hemorrhagic content (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThis finding in the suspicion of active DIE plaque also appears to be related to the root of the ischial nerve. We conclude the MR report describing a condition of endometriosis affecting both intra-pelvic median and posterior compartment and extra-pelvic lateral compartment involving right sciatic nerve near the homolateral sciatic foramen.\u003c/p\u003e \u003cp\u003eOur patient underwent surgical laparoscopic approach with the excision of the posterior DIE and nerve sparing surgery to remove the sciatic nodule; histological findings confirmed sciatic nerve endometriosis. The symptoms were resolved after surgical treatment and the patient started continuous progestin-based hormonal treatment to avoid disease relapse.\u003c/p\u003e \n\u003cp\u003e\u003cem\u003eDiscussion\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe sciatic nerve, the largest somatic nerve in the human body, was first linked to cyclical sciatica in a case reported by Head et al. in 1962 [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The exact mechanism behind the sciatic localization of endometrial cells remains unclear. One theory suggests migration of endometrial cells from pelvic endometriotic lesions, while other hypotheses propose mechanisms such as hematogenous spread, coelomic metaplasia, or embryonic cell remnants [\u003cspan additionalcitationids=\"CR38\" citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Additionally, Possover et al. introduced a \"neurologic hypothesis\" in 2007, describing a case of isolated sciatic nerve endometriosis with no detectable pelvic endometriotic lesions [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe most frequent site of sciatic nerve involvement in endometriosis is near the greater sciatic foramen, with the right sciatic nerve being more commonly affected than the left. [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Cyclical bleeding into adjacent tissues leads to inflammation, fibrosis and scarring, which exacerbate nerve compression over time.\u003c/p\u003e \u003cp\u003eThe diagnosis of sciatic nerve endometriosis is based on clinical symptoms and imaging studies, with histopathological examination providing definitive confirmation. Key clinical indicators include sciatica that follows a cyclical pattern related to menstruation. As the condition progresses, pain-free intervals shorten, and the pain becomes persistent, though it continues to worsen during menstruation.\u003c/p\u003e \u003cp\u003eMRI is the preferred imaging modality for detecting sciatic endometriosis, offering a sensitivity of 90% and a specificity of 98% [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The appearance of endometriotic lesions varies with the stage of hemorrhage, typically showing high signal intensity on T1-weighted images and a combination of high and low signal intensities on T2-weighted images. Importantly, the absence of pelvic endometriosis does not rule out sciatic nerve involvement [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSurgical treatment depends on the extent of the disease. If only the pelvic portion of the sciatic nerve is affected, a skilled gynecologist can perform a laparoscopic or robotic procedure [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. when the extra-pelvic portion or both pelvic and extra-pelvic parts of the nerve are involved, a trans-gluteal surgical approach is required. In such cases, a multidisciplinary team comprising neurosurgeons and orthopedic specialists is essential. [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn conclusion, sciatic nerve endometriosis should be considered in patients presenting with sciatica exhibiting a cyclical pattern. MRI serves as the optimal imaging modality to support the clinical diagnosis. Treatment requires the involvement of a multidisciplinary surgical team with a thorough understanding of retroperitoneal neuroanatomy. The choice of surgical approach, whether laparoscopic or trans-gluteal, should be carefully planned prior to the procedure. Early diagnosis, timely intervention, and comprehensive post-operative physiotherapy can significantly enhance recovery outcomes for these patients.\u003c/p\u003e\u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Case 3: Anterior lateral compartment abdominal wall and inguinal endometriosis\u003c/h2\u003e \u003cp\u003e \u003cem\u003eClinical Case\u003c/em\u003e \u003c/p\u003e \u003cp\u003eA 44-year-old patient presented with heavy menstrual periods. The patient had experienced two spontaneous pregnancies and deliveries and presented with a current medical history of systemic lupus erythematosus under treatment.\u003c/p\u003e \u003cp\u003eAt the first clinical evaluation she complained of dysmenorrhea (Visual Assessment Score, VAS 9), dyspareunia (VAS 7), with no dyschezia or dysuria. She also complained of severe pain (VAS 10) in the right inguinal region, during menstrual phase. She had never taken hormonal treatments.\u003c/p\u003e \u003cp\u003eBecause of these invalidating symptoms she underwent transvaginal ultrasound evaluation (TVS) which showed a globose uterus presenting fibromatosis and direct signs of adenomyosis; a hypoechoic nodule of 10x9x4 mm in size at the level of the torus uteri and an analogous nodule of 15x8x9 mm in size in the posterior vaginal fornix were detected. Ovaries were regular. In the right inguinal region, a painful hypoechoic nodule of 39x14 mm in size, with irregular margins, moderately vascularized at color-Doppler US, was observed.\u003c/p\u003e \u003cp\u003eAll these findings led to the suspicion of pelvic DIE. The probability of an extrapelvic endometriosis, as inguinal endometriosis localization, was high and an indication to carry out an MR exam was given. She was referred to dedicated radiologist to perform MR.\u003c/p\u003e \u003cp\u003eThe MR exam was performed with T1 fat saturation and T2 sequences in axial, coronal and sagittal planes without contrast medium agent (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). MRI showed an ovoid mass localized in the anterior abdominal wall which infiltrated the edge of the rectus abdominis muscle and extended to the wall of right inguinal canal with probable involvement of the pubic nerve as hypothesized from clinical symptoms. The MR images, according with US, were compatible with a localization of endometrial glands as a glandular-cystic plaque, due to typical MRI features. Contrast medium agent was not used.\u003c/p\u003e \u003cp\u003eBased on the absence of previous surgery, clinical symptoms, US and MRI features, our diagnostic hypothesis was endometriosis of the canal of Nuck (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eAfter diagnosis, the patient started a continuous progestin-based hormonal treatment for 12 months, inducing amenorrhea, with improvement of dysmenorrhea but with persistence of dyspareunia and inguinal pain. Due to the persistence of symptoms the patient underwent laparoscopy to remove DIE and groin incision to remove inguinal endometriosis.\u003c/p\u003e \u003cp\u003eAt the follow-up evaluation symptoms were reduced (dysmenorrhea VAS 5, dyspareunia VAS 4, and absent inguinal pain).\u003c/p\u003e \u003cp\u003e \u003cem\u003eDiscussion\u003c/em\u003e \u003c/p\u003e \u003cp\u003eEndometriosis of the inguinal region may involve inguinal hernia sac, canal of Nuck, uterine round ligament (RLUs) and subcutaneous tissue [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eInguinal endometriosis (from the labia majora to the abdominal wall) is a very unusual extrapelvic site for endometriosis, with incidence\u0026thinsp;\u0026lt;\u0026thinsp;0.1% [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. Incomplete obliteration of the canal of Nuck is known as a patent processus vaginalis and can result in either an inguinal hernia or a hydrocele in female children. It can provide a pathway for superficial inguinal endometriosis [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. RLUs have an intrapelvic and an extrapelvic portion where the extrapelvic one is the distal part of the ligament in the canal of Nuck [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Endometriosis from RLUs may advance through the inguinal ring into the inguinal canal, and this may be an anatomical pathway for endometrial implants to the superficial inguinal soft tissues [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. Symptoms of endometriosis of the intrapelvic portion of the RLUs are nonspecific, usually referred as pain localized in the lower abdomen [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Our patient had severe groin pain during menstrual cycle, associated with superficial swelling at the right inguinal level.\u003c/p\u003e \u003cp\u003eOn sonographic imaging our patient had a solid (hypoechoic) nodule, with irregular margins, moderately vascularized on color doppler. Nevertheless, the sonographic appearance of inguinal endometriosis is not typical, varying between a predominantly solid, a cystic or combined mass [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. When extra-pelvic endometriosis is suspected the integration of US and MRI, like in our case, is the best approach in the diagnostic workup [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e],[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. Differential diagnosis includes abdominal wall masses, such as hernias, lipomas, sebaceous cysts hematomas, and malignant tumors [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur patients underwent first line medical treatment and subsequently surgery. As suggested by Delkalitsis et al, while other treatment modalities like hormonal suppressive therapy remain to be evaluated, surgical treatment consists of excision of the mass from the canal of Nuck and subcutaneous lesions is the better choice in case of severe symptoms [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eThe diagnostic role of MR in endometriosis is evolving, necessitating radiologists to possess a meaningful understanding of the several clinical and imaging manifestations associated with both typical and atypical localizations. This becomes particularly crucial when assessing patients with clinical suspicion of DIE. Radiologists must diligently explore, document, and stratify the disease across a spectrum of locations in endometriosis patients. Accurate diagnosis holds paramount significance for steering appropriate patient management. While laparoscopy remains the benchmark for endometriosis diagnosis, certain diagnostic challenges exist, such as the potential oversight of nodules concealed by adhesions and subperitoneal disease.\u003c/p\u003e \u003cp\u003eSuccessful treatment strategies encompass hormonal-based therapies including combined oral contraceptives (COC), progesterone agents, alongside lesion removal with radical surgery. In instances where surgery is indicated, MRI serves as a valuable tool, providing a comprehensive roadmap. This facilitates effective presurgical counseling and empowers the surgeon in the meticulous eradication of all endometriotic implants. The integration of MRI into the diagnostic and therapeutic framework enhances precision and contributes significantly to the overall management of endometriosis.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eInformed consent\u003c/h2\u003e\n\u003cp\u003eThe patient(s), or their next of kin, or their legal representative(s) signed:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e- written informed consent for the performance of contrast-enhanced MRI.\u003c/p\u003e\n\u003cp\u003e- written informed consent to the use of images for research purposes and scientific description (attached below).\u003c/p\u003e\n\u003cp\u003eThe privacy of the patient has been assured in all materials.\u003c/p\u003e\n\u003cp\u003eWritten informed consent forms from the patient(s) and/or their legal representative(s)/guardian(s) are preserved in our department archive (U.O.C. Diagnostic Imaging, PTV Policlinico \u0026ldquo;Tor Vergata\u0026rdquo; University, Viale Oxford 81, 00133, Rome, Italy)\u003c/p\u003e\n\u003ch2\u003eEthics\u003c/h2\u003e\n\u003cp\u003eThe need for ethical approval was waived off by the ethical committee \u0026ldquo;CET Lazio Area 2\u0026rdquo; of Roma Tor Vergata University because our study is a case series, and we iconographically describe images acquired during routine MRI examinations. As the study relies on standard clinical practice, it does not require approval from the ethics committee.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eAll authors contributed equally to the work. The tasks were divided as follows:F.R, F.M and C.R wrote the main manuscript text under the supervision of R.M and V.F, radiologists with over 10 years of experience in diagnostic imaging of the female pelvis.C.P.R. Conducted multiple ongoing reviews of the manuscript with particular attention to scientific terminology and English language.M.L prepared figures 1-4 and Article layoutF.G and G.M conducted the final review\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eAs per the Ministerial Decree of February 14, 1997, all MRI images of the reported cases will be stored in the digital archive of our polyclinic for 10 years.The clinical data collected will be gathered by the Research Center and processed there. The Data Protection Officer for the healthcare company can be contacted upon reasonable request.The informed consents will be archived in the archive of our polyclinic as per Law No. 219 of December 22, 2017\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFeldman MK, VanBuren WM, Barnard H, Taffel MT, Kho RM. 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PMID: 35181041\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGui B, Valentini AL, Ninivaggi V, Micc\u0026ograve; M, Zecchi V, Grimaldi PP, Cambi F, Guido M, Bonomo L. Shining light in a dark landscape: MRI evaluation of unusual localization of endometriosis. Diagn Interv Radiol. 2017 Jul-Aug;23(4):272\u0026ndash;281. doi: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.5152/dir.2017.16364\u003c/span\u003e\u003cspan address=\"10.5152/dir.2017.16364\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. PMID: 28703103; PMCID: PMC5508950.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Medicine](https://link.springer.com/journal/44337)","snPcode":"44337","submissionUrl":"https://submission.springernature.com/new-submission/44337/3","title":"Discover Medicine","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-5595138/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5595138/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eEndometriosis affects approximately 10% of women of reproductive age and is a significant cause of pelvic pain and infertility. It manifests in three patterns: superficial peritoneal lesions, ovarian endometriomas, and deep infiltrating endometriosis. Our aim is to remind radiologists of the possibility of atypical locations of pelvic and extrapelvic endometriosis and to illustrate their characteristics on magnetic resonance imaging.\u003c/p\u003e\n\u003cp\u003eThe most common site of endometriosis is the ovaries, followed by the pelvic peritoneum. Less common locations include deep subperitoneal tissues, the gastrointestinal tract, the bladder, the thorax, and subcutaneous tissues. We present three rare clinical cases: diaphragmatic endometriosis, inguinal canal endometriosis, and a case of sciatic nerve infiltration. MRI imaging provides important findings that help classify the disease and identify the extent of the lesion, thus facilitating appropriate diagnosis and treatment. Radiologists should be familiar with the MRI imaging findings of deep infiltrating endometriosis in various anatomical sites to provide information that allows for adequate pre-surgical counseling.\u003c/p\u003e","manuscriptTitle":"Extragenital and Extrapelvic Endometriosis: Literature Update and Mri Immaging Case Collection of Unusual Localizations","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-01-02 09:03:29","doi":"10.21203/rs.3.rs-5595138/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-03-10T06:20:07+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-02-05T07:01:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"125701174863631533623631465353132741098","date":"2025-02-03T11:57:58+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-01-26T13:26:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"280640239202379011495003512321944246379","date":"2025-01-14T15:53:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"128347684417972731873239016092601187944","date":"2025-01-14T08:19:23+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-01-09T16:39:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"288103772361818986977209787242683273525","date":"2025-01-08T18:46:58+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-01-08T09:20:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-01-01T05:39:06+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-12-31T11:42:40+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Medicine","date":"2024-12-06T16:36:44+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-medicine","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Medicine](https://link.springer.com/journal/44337)","snPcode":"44337","submissionUrl":"https://submission.springernature.com/new-submission/44337/3","title":"Discover Medicine","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a355d2a0-2967-4657-9226-a7c031907767","owner":[],"postedDate":"January 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-07-12T06:53:22+00:00","versionOfRecord":[],"versionCreatedAt":"2025-01-02 09:03:29","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5595138","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5595138","identity":"rs-5595138","version":["v1"]},"buildId":"_2-kVJe1T_tPrBINL-cwx","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}