Endometriosis of the vermiform appendix: a rare cause of acute abdomen in women – case report and review of literature

Isolated appendicular endometriosis (AE) is a very rare diagnosis, representing less than 1% of extra-pelvic endometriosis[]. Endometriosis is the presence of functional endometrial tissue located outside the lining of the uterine cavity[]. HIGHLIGHTS Appendicular endometriosis mimicking appendicitis is very rare. It has been reported only 44 times in the literature from 1975 to 2021. It is one of the causes of acute and chronic recurrent pelvic pain, associated with a reduced quality of life, which improves after appendectomy. Case presentation: We present a rare case of isolated appendicular endometriosis in a 19-year-old female, proven by histopathological examination, together with a short review of the literature. Appendicular endometriosis is associated with higher rates of perforation and abscess formation, and appendectomy should be considered if the appendix appears abnormal and is sent for histopathological examination. It is a common disorder affecting 10% of women of reproductive age. Isolated (AE) has been reported only 44 times in the literature[]. Acute appendicitis (AA), on the other hand, is the most common surgical cause of acute abdominal pain. AE is a rare finding[]. Isolated AE is usually asymptomatic, although one-third may experience cyclic right iliac fossa pain[]. Endometriosis is an estrogen-dependent disease defined by the presence of endometrium-like epithelium and/or stroma outside the endometrium and myometrium. Common sites are the ovaries, fallopian tubes, pelvic peritoneum, and uterosacral ligaments, whereas the atypical sites of endometriosis include the gastrointestinal tract, urinary tract, soft tissues, and chest[]. Implantation in the GIT is rare, with isolated AE occurring in less than 1%[]. The case We present a rare case of isolated AE in a 19-year-old female, proven by histopathological examination, together with a short review of the literature (2018 ICD-10-CM Diagnosis Code N80). AE mimicking appendicitis is very rare. It is one of the causes of acute and chronic recurrent pelvic pain, associated with reduced quality of life, which improves after appendectomy[]. Definitive diagnosis is established by laparoscopy and histopathological examination of the removed appendix[,]. Endometriosis is usually associated with primary infertility. Acute appendicitis accounts for 75% of cases of acute abdomen in pregnancy. If a lady gets pregnant, appendicitis due to endometriosis in pregnancy is estimated to occur in only 3–8 per 10 000 deliveries[]. A 19-year-old female, recently married (2 months ago), experienced sudden diffuse abdominal pain of 1-day duration associated with nausea and anorexia. The pain became localized to the right lower quadrant after 24 hours. It was not responding to simple analgesics. There was no medical or surgical past history of significance. The patient reported having spasmodic dysmenorrhea but did not seek medical attention as she thought it was normal for her age. Examination The patient was hemodynamically stable and afebrile. There was localized tenderness and rebound tenderness at the right iliac fossa and a positive psoas sign. LABS/RAD HB 12.5 g/dL, HCT 40.8%, WBC 9.9 thousand/cmm, PLT 301 thousand/cmm, CRP 1.7 mg/dL, and beta HCG 2.39 mIU/mL. Abdominal ultrasound was normal. It showed no radiological signs of appendicitis. Management Patient was admitted to the hospital for observation, but due to persistent signs and symptoms, she was offered a laparoscopic appendicectomy as the symptoms were typical and showed no improvement with analgesia. After informed consent, the patient underwent a laparoscopic appendectomy. She had an uneventful postoperative period and was discharged in stable condition the next day. Intraoperative and postoperative findings Drumstick appearance or club-shaped appendix with an enlarged but intact end (Fig. 1), mild pelvic non-hemorrhagic reaction – free fluid in Douglas pouch. Both ovaries looked normal, with the normal position and shape of the uterus. There were no obvious endometriotic lesions. Laparoscopic appendectomy was carried out in the usual way by dividing the mesoappendix using Ligasure©, then ligation of the stump by endoloop and amputation of the appendix with delivery of the specimen through a retrieval bag. It was sent for histopathological examination, especially due to its abnormal appearance. The patient had an uneventful postoperative recovery and was discharged on the first postoperative day. Later, in the follow-up, she reported the disappearance of spasmodic dysmenorrhea, and no further treatment was needed. Pathology report Histopathological report showed endometriosis of the wall of the vermiform appendix with associated acute suppurative appendicitis, as shown in Figure 2. The specimen showed congested blood vessels; the mucosa showed ulceration and shedding, and the submucosa showed hyperplasia of the lymphoid follicles. There were no neuroendocrine tumors. Cut sections showed narrowing of the appendix lumen (Fig. 3).

We present a rare case of isolated appendiceal endometriosis. Endometriosis is the presence of functional endometrial tissue located outside the lining of the uterine cavity[]. Common sites of endometriosis are the ovaries, fallopian tubes, pelvic peritoneum, and uterosacral ligaments (also known as the “pelvic” site), whereas the atypical sites of endometriosis include the gastrointestinal tract, urinary tract, soft tissues, and chest (alternatively referred to as the “extra-pelvic” site)[]. It is a well-known cause of chronic pelvic pain and infertility in females. Endometriosis of the appendix is rare and may present with acute or chronic abdominal pain[]. AE mimicking appendicitis is very rare. It has been reported only 44 times in the literature from 1975 to 2021. Endometriosis in the appendix was first reported by von Rokitansky in 1860[]. The definitive diagnosis is usually established following the histopathological examination of the appendix[,]. Laparoscopy is the procedure of choice for the diagnosis and surgical treatment of endometriosis of the appendix[]. In our case, there was an isolated AE. Our patient actually reported relief from spasmodic dysmenorrhea and chronic pelvic pain despite not having other sites of endometriosis, except the isolated appendicular focus. We think that AE is associated with chronic and recurrent pelvic pain, higher rates of perforated appendicitis, and abscess formation, and the condition should be considered and treated promptly. If, during laparoscopy, the appendix appears abnormal, it should be removed and sent for histopathological examination. The pathophysiology of endometriosis is not well-elucidated[]. The most widely accepted theories are enumerated in Table 1. Table 1 Theories proposed for the etiology of endometriosis[]. | Theory | Mechanism proposed | |---|---| | Retrograde menstruation | Retrograde menstruation permits implantation of endometrial glands and stroma into the peritoneal cavity. | | Coelomic metaplasia theory | Endometriosis can develop in all celomic wall derivatives because of a metaplastic phenomenon. | | Hematogenous lymphatic spread theory | Dissemination of endometrial cells takes place by lymphatic or hematogenous vessels. | | Stem cell recruitment theory | Endometrial and/or hematopoietic stem cells could differentiate into endometriotic tissue at different anatomical sites. | | Embryogenic theory | Persistence of residual embryonic cells of Wolffian or Müllerian ducts may develop into endometriotic lesions in response to estrogen. | It was suggested that, due to the high prevalence of endometriosis of the appendix in women with endometriosis, an incidental appendectomy at the time of surgery may serve as both a preventive and therapeutic measure. Appendectomy was performed if the appendix appeared to be abnormal and showed appendiceal adhesions, rigidity, hyperemia, congestion, induration, or implants of endometriosis. In general, the treatment strategies for endometriosis are determined individually, depending on the desire for children and the stage of the disease. Endometriosis treatments include supportive care, medication, and surgery. On the other hand, acute appendicitis is the most common diagnosis in young women presenting with acute right lliac fossa (RIF) pain at the emergency department. It is estimated that appendiceal endometriosis occurs in about 3% of women who undergo appendectomy for RIF pain. This percentage increases to 12% after detailed histopathological examination of the removed appendix. Acute appendicitis generally requires prompt surgery, which is the gold standard treatment, and no consensus has been reached on the role of non-operative management.[] Involvement of the appendix may present as appendicitis, mucocele of the appendix, or an appendicular mass that may mimic a neoplasm. Perforation of the appendix may occur, especially during the first two trimesters of pregnancy[]. There were two issues to be addressed in cases of AE. First is the prevalence of endometriosis of the appendix as an incidental finding in gynecological surgery. Second is the safety of appendectomy in women operated on for endometriosis (incidental or opportunistic appendectomy). In several published series, the incidence of AE ranged from 1% to 44%. This percentage rose to 75% to 80% after detailed histological examination of the removed appendices, with 89% relief of chronic pelvic pain after 1 year follow-up[]. Concerning the safety of appendectomy at the time of surgery for endometriosis, a few researchers have advocated for elective appendectomies in women with chronic pelvic pain. Appendectomy at the time of primary gynecologic surgery is safe and does not increase the risks of the procedure. Additionally, several studies have shown that appendectomy does not significantly increase operating times[]. Pathophysiology Endometriosis of the appendix is divided into primary and secondary forms. The primary form shows histopathological evidence of endometriosis within the appendix, with no clinicopathological evidence of extra-AE. The secondary form is associated with internal and/or external endometriosis. Moreover, most patients diagnosed suffer from menstrual irregularities and uterine myomatosis. Patients with appendiceal endometriosis (AE) can be divided into four groups, according to symptoms:[,] Asymptomatic patients. Patients with classic acute appendicitis. Patients with invagination of the appendix into the cecum or cecal intussusception. Patients with atypical symptoms, including melena and intestinal perforation, as well as tumor-like tissue infiltrating surrounding structures[,]. Isolated AE is usually asymptomatic[]. The most commonly observed group consists of patients who present with appendicitis, with the condition occurring mainly during menstruation. Symptoms are caused by endometrial bleeding within the seromuscular layer, followed by edema, obstruction, and inflammation, leading to partial or complete occlusion of the appendiceal lumen[]. Sporadic cases of appendicular decidua have been reported in pregnancy, resulting in acute appendicitis during pregnancy. During pregnancy, circulating progesterone stimulates decidualization of endometrial tissue, creating a favorable environment for embryo fertilization. Two mechanisms have been described by which decidualized endometriosis produces appendicular inflammation. The first is volume expansion of endometrial tissue undergoing decidualization, causing extrinsic compression of the appendiceal lumen. The second is the presence of an intraluminal endometrial polyp. The final common pathway is increased intraluminal pressure, mucosal ischemia, bacterial proliferation, and inflammation. Altered antigenicity produces proliferation of Natural Killer cell expression, resulting in a high rate of appendicular perforation and abscess formation[]. Diagnosis and differential diagnosis Diagnostic options such as patient history, physical examination, blood tests (CA-125), colonoscopy, ultrasound, tomography, and magnetic resonance imaging may be useful for making the diagnosis of endometriosis. Definitive diagnosis is achieved through diagnostic laparoscopy and histopathological examination of the appendix. The differential diagnosis of intestinal endometriosis includes inflammatory bowel disease, diverticulitis, ileo-colonic tuberculosis, schistosomiasis, benign and malignant neoplasms, and colonic ischemia[]. Treatment Appendectomy may be considered as part of the surgical ablation of endometriosis after proper patient counseling[]. As patients with endometriosis experience a high rate of reoperation, incidental appendectomy has been shown to be beneficial in reducing pain in a subset of women with chronic pain in the right lower quadrant[,]. Laparoscopic surgery is useful in women with chronic abdominal pain, as in the present case, as it enables the entire peritoneal cavity to be explored and a definitive diagnosis to be made. Laparoscopic appendectomy is the treatment of choice in these cases. Further medical treatment by a specialized gynecologist should be considered following surgery in patients with symptomatic endometriosis[]. The work has been reported in line with the SCARE criteria[].

This is a rare case of isolated AE. Although rare, endometriosis of the appendix can present either as isolated AE or as part of pelvic endometriosis, in a single, pregnant, or even post-menopausal woman. It is a cause of lower quadrant abdominal pain that should always be considered in the differential diagnosis of young women complaining of nonspecific recurrent lower abdominal pain, especially with infertility. AE is associated with higher rates of perforated appendicitis and abscess formation, and the condition should be thought of and treated promptly. If, on laparoscopy, the appendix appears abnormal, it should be removed and sent for histopathological examination. Ethical approval Not available. The file is not available partially because of patient confidentiality rights and because this case was done while I was practicing in another country. Consent Consent was granted by the patient. Author contributions Not applicable. Sources of funding This is self-funded research. Conflicts of interest disclosure Not applicable. Research registration unique identifying number (UIN) Not applicable. Provenance and peer review Double anonymized peer reviewed. Guarantor Hany Mohamed Elbarbary. Data availability statement Not applicable.

I wish to acknowledge Prof Dr Abeer Abdelmohsen, Professor of Histopathology, Ain Shams University, for labeling the pathology slides.

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