Pelvic splenosis implanted in Douglas pouch mimics pseudo-endometriosis symptoms: a case report study

The entire process of data collection and publication was supervised by the Ethics Committee of the University. Written consent was also obtained from the patient. Other identification details remained confidential. This case report described the referral and subsequent hospital admission of a 43-year-old married woman. The patient contained two children with a history of two cesarean sections (the last cesarean section was conducted in 2020). During second cesarean section, an incidental mass was detected in the retrouterine cavity. This abnormal finding was ignored by the patient due to the absence of pain. The patient also had an accident (in 1987 at the age of 5 years) with acute splenic injury and extensive splenic rupture followed by splenectomy. In January 2025, following acute pelvic pain during the last month, the patient was referred to the medical center with symptoms of hypomenorrhea and dysmenorrhea. After initial medical assessments, the patient was referred to the imaging and laboratory centers for further evaluation. Using transvaginal Doppler ultrasonography technique (Fig. 1 A–C), two non-solid masses with smooth surfaces (Fig. 1 A and B), multiple septation, and hyper-vascularization (Fig. 1 C) were detected in the cul-de-sac pouch (Fig. 2 B). The dimensions and location of the masses were detected as follows (Fig. 2 A and C); a large mass (implanted in the right side at the junction between bilateral uterosacral ligament and posterior wall of cervix, with dimensions of 64.86 × 37.08 mm) and a small mass (located at the left side of posterior wall of cervix with dimensions of 36.90 × 46.41 mm). Both masses were implanted in cul-de-sac pouch. Serological assays also showed normal levels of CA125 (~31 U/mL), αFP (~8 ng/mL), and CEA (~3.2 μg/L) demonstrating a lack of any tumors or fetus. Uterine evaluations also approved anatomical dimensions with normal endometrial structure. Figure 1. Transvaginal ultrasonography and color Doppler sonography techniques. Post-uterine masses (A, B) in cul-de-sac pouch with high rates of vascularization (C). Yellow arrows indicate the size of masses (A: 64.86 × 37.08 mm and B: 36.90 × 46.41 mm) and the yellow dotted line represents the span of splenosis. Figure 2. Photographs of excised tissues containing splenosis and internal reproductive organs. The splenosis fragments were implanted in Douglas pouch. (A) Anterior view of uterus and cervix post-surgery, (B) superior view of Douglas pouch prior to surgery, and (C) posterior view uterus and cervix post-surgery. Black, yellow, blue, red, and green arrows respectively indicate the fallopian tube, uterus, cervix, posterior part of the uterus, and Douglas pouch. White dotted lines represent the span of splenosis fragments. Transvaginal ultrasonography and color Doppler sonography techniques. Post-uterine masses (A, B) in cul-de-sac pouch with high rates of vascularization (C). Yellow arrows indicate the size of masses (A: 64.86 × 37.08 mm and B: 36.90 × 46.41 mm) and the yellow dotted line represents the span of splenosis. Photographs of excised tissues containing splenosis and internal reproductive organs. The splenosis fragments were implanted in Douglas pouch. (A) Anterior view of uterus and cervix post-surgery, (B) superior view of Douglas pouch prior to surgery, and (C) posterior view uterus and cervix post-surgery. Black, yellow, blue, red, and green arrows respectively indicate the fallopian tube, uterus, cervix, posterior part of the uterus, and Douglas pouch. White dotted lines represent the span of splenosis fragments. Based on the suggestion of the healthcare team, an exploratory laparotomy was performed (under general anesthesia). Retrouterine pouch was exposed and the proliferated masses were detected (Fig. 2 B). Two distinct brown masses with smooth and uniform surfaces were firmly attached to the posterior wall of the uterus and parametrium (Fig. 2 A and C). The structure of mass was well-defined and non-encapsulated. Due to high adhesion to the uterus, total hysterectomy along with bilateral salpingo-oophorectomy were performed as suggested therapeutic surgical procedures (Fig. 2 A and C). A cut of the specimen was provided and fixed in formalin for further histopathological evaluations. The specimen was stained using the H&E technique and pathological evaluation was performed. In this section, distinct red and white pulps, separated by a marginal zone, were clearly detected. In red pulp, cords of Billroth and venous sinuses were found microscopically. Lymphoid follicles and marginal zones along with lymphocyte aggregations were also found in histological sections. Finally, the mass with non-anatomical macroscopic features (including no splenic capsule and hilum) along with microscopic characteristics was diagnosed as an implanted spleen (Fig. 3 ). Thus, splenosis was detected and the patient with stable health features was discharged from the hospital. Two months’ patient follow-up showed no abnormal changes. Figure 3. Histopathological sections of splenosis following tissue excision. Yellow, Black, and red arrows, respectively, indicate red pulp, white pulp, and marginal zone. (A) 40× magnification of splenosis section with the focus on white and red pulp and (B) 100× magnification of tissue representing the lymphocyte aggregations. Histopathological sections of splenosis following tissue excision. Yellow, Black, and red arrows, respectively, indicate red pulp, white pulp, and marginal zone. (A) 40× magnification of splenosis section with the focus on white and red pulp and (B) 100× magnification of tissue representing the lymphocyte aggregations.

The spleen is a vital organ in immune and hematologic systems with compact aggregations of lymphocytes. An accessory spleen, or splenule, is a small nodule of splenic tissue separate from the main spleen, occurring in about 10% of the population [ 1 ] . Besides, the term “Splenosis” refers to autotransplantation and implantation of displaced fragments of spleen following acute trauma and rupture. Splenosis nodules lack a capsule and vascular hilum, often implanting on well-vascularized surfaces in pelvic space, generally Cul-de-sac [ 2 ] . According to the specific regions of implanted splenosis and the associated anatomical relations, the referred pains appear leading to misdiagnosis of the pathology [ 3 ] . In the present case report study, the authors aimed to report a misdiagnosed pseudo-endometriosis in a woman with pelvic splenosis due to the presence of anatomical relations of implanted splenosis with internal reproductive organs. The conducted surgical procedure was proposed as the proper treatment in this regard. HIGHLIGHTS Pelvic splenosis is a benign condition characterized by heterotopic intrapelvic autotransplantation of splenic tissue. Displaced splenic fragments are typically formed following traumatic rupture. The presence of pelvic splenosis and progression into the uterus and ovaries can potentially mimic pseudo-endometriosis symptoms. Splenectomy for abnormal pelvic splenosis is proposed for the associated cases. Pelvic splenosis is a benign condition characterized by heterotopic intrapelvic autotransplantation of splenic tissue. Displaced splenic fragments are typically formed following traumatic rupture. The presence of pelvic splenosis and progression into the uterus and ovaries can potentially mimic pseudo-endometriosis symptoms. Splenectomy for abnormal pelvic splenosis is proposed for the associated cases. Pelvic splenosis is a benign condition characterized by heterotopic intrapelvic autotransplantation of splenic tissue. Displaced splenic fragments are typically formed following traumatic rupture. The presence of pelvic splenosis and progression into the uterus and ovaries can potentially mimic pseudo-endometriosis symptoms. Splenectomy for abnormal pelvic splenosis is proposed for the associated cases.

This case report study demonstrated a patient diagnosed with splenosis with pseudo-endometriosis symptoms. The assessments showed that following spleen damage during a car accident, some splenic fragments were probably displaced in the intraperitoneal cavity and implanted in retrouterine pouch. This phenomenon caused vast angiogenesis leading to successful tissue implantation. Some decades later, splenic tissue proliferation was applied and the symptoms appeared. Due to the anatomical relations of spleen implantation site (cul-de-sac) with uterus and ovaries, pseudo-endometriosis symptoms were detected as the primary diagnosis. Following diagnostic sonographic and serological tests, tissue excision operation along with total hysterectomy and bilateral salpingo-oophorectomy was managed. Finally, the patient was discharged from the hospital with no complications. The spleen is a multifunctional abdominal organ integral to hematological filtration and immunological defense. Its anatomical position and vascular nature render it susceptible to traumatic injury, with clinical implications ranging from acute hemorrhage to compensatory mechanisms like splenosis. The spleen’s fragility arises from its capsular thinness, which has limited tensile strength against blunt force, and its high vascularity accounts for approximately 1% of cardiac output, increasing the risk of hemorrhage upon injury [ 4 ] . Additionally, disease-related enlargement, such as infectious mononucleosis [ 5 ] or hematologic malignancies, causes splenomegaly predisposing to spontaneous rupture [ 6 ] . Blunt abdominal trauma, mainly car accident, accounts for most splenic injuries. Splenosis refers to the ectopic implantation of splenic tissue following traumatic or iatrogenic rupture, occurring in 65% of splenic trauma cases [ 7 ] . This phenomenon involves the dispersal of splenic fragments that vascularize in sites such as the peritoneal cavity. Splenosis may confer residual immune function, potentially mitigating post-splenectomy infection risks. Splenectomy is required for hemodynamically unstable patients but increases lifelong susceptibility to encapsulated bacterial infections. Hemodynamically stable patients with low-grade injuries may undergo embolization or observation [ 8 ] . Pseudo-endometriosis refers to conditions that mimic endometriosis but are not caused by the ectopic growth of some other tissues such as splenic fragments. Splenosis, the autotransplantation of splenic tissue following splenic trauma or surgery, is a rare condition that can mimic endometriosis when located in atypical sites, such as the retrouterine pouch [ 9 ] . Pseudo-endometriosis can present with symptoms similar to true endometriosis due to its location and interaction with surrounding pelvic structures. These include chronic or cyclical pelvic pain, often exacerbated during menstruation, mimicking dysmenorrhea [ 3 , 10 ] . Additionally, dyspareunia is common, with deep pelvic pain during or after sexual intercourse due to irritation or inflammation in the retrouterine pouch [ 9 ] . Menstrual irregularities such as menorrhagia or spotting between periods may occur if adjacent tissues are inflamed [ 11 ] . In some cases, pseudo-endometriosis can contribute to difficulty conceiving due to pelvic adhesions or inflammation. Other symptoms include fatigue, nausea, bloating, and urinary symptoms such as dysuria, depending on the extent of tissue involvement [ 12 ] . Splenosis is often asymptomatic but can become symptomatic when located in sensitive areas like the retrouterine pouch. Symptoms include non-cyclical chronic pelvic pain due to mass effect or irritation of surrounding tissues. Pain may be mistaken for endometriosis because of its location [ 9 ] . A palpable mass in the pelvis may be detected during physical examination, and compression of adjacent organs can lead to bowel or bladder dysfunction. Although rare, splenosis may cause menstrual irregularities or mimic gastrointestinal symptoms such as constipation or diarrhea [ 9 ] . A history of splenic trauma or splenectomy is a key diagnostic clue, as splenosis results from autotransplantation of splenic tissue. The overlapping presentation of pseudo-endometriosis and splenosis with true endometriosis necessitates careful evaluation. Differential diagnoses include true endometriosis, pelvic inflammatory disease, ovarian cysts, uterine fibroids, and gastrointestinal disorders such as irritable bowel syndrome. Imaging techniques such as ultrasound and MRI are helpful in identofocation of pelvic masses but may not differentiate between endometriosis and splenosis [ 13 ] . CT scans with contrast can reveal ectopic splenic tissue based on its characteristic enhancement pattern. Laparoscopy remains the gold standard for diagnosing both conditions, allowing direct visualization and biopsy. Histopathological examination confirms splenic tissue in cases of splenosis [ 11 , 14 ] .

Ruptured spleen can mostly displace and implant in Douglas pouch, in relation to the uterus and ovaries. This case report showed that implanted spleen fragments in the vicinity of internal reproductive organs can potentially mimic endometriosis-like symptoms. This diagnostic differentiation between pelvic splenosis and pseudo-endometriosis in patients with ruptured spleen seems a critical note for clinicians.