Rectosigmoid endometriosis, a rare cause of lower GI bleeding in a premenopausal woman: Case report

A 35-year-old female, Para 1 + 2 Living 1, presented with a 4-year history of chronic abdominal pain. The pain was colicky, located in the hypogastric and umbilical regions, radiating to the perianal area, and was notably worse during her menstrual cycle. Along with the pain, she experienced alternating bowel habits, characterized by episodes of loose stools followed by constipation, with the stools described as hard, goat pellet-like, and black, accompanied by a foul odor. The patient denied any associated symptoms such as nausea, vomiting, abdominal distention, or weight loss. There was no history of dyspnea, periodic cough or history of blood in sputum. She does not smoke or consume alcohol; she did not report any family history of gastrointestinal or gynecological diseases. The patient attained menarche at the age of 14 with initially regular menstrual cycles of 28 days and an average flow lasting 4 days. In recent years, her cycles became irregular, ranging from 21 to 28 days, with heavy menstrual bleeding lasting for 7 days and requiring the use of 5 fully soaked sanitary pads per day. She reported associated symptoms of anemia with usual Hb on her visits never exceeding 9 g/dl, including fatigue and paleness. Her obstetric history included one healthy 10-year-old child, along with two spontaneous miscarriages in the first month of gestation, one 8 years prior and another 2 years later. Despite her ongoing symptoms, her gynecological evaluations, including routine ultrasounds, were normal. After experiencing no improvement from gynecological consultations, the patient was referred to a gastroenterologist, who recommended a colonoscopy and abdominal CT scan afterwards. This procedure revealed a rectosigmoid polypoid mass with intact mucosa and partially obstructing the lumen measuring about 5 cm, 15–20 cm from anal verge ( Fig. 1 ), which was biopsied. The biopsy showed unspecific inflammatory changes with no epithelial dysplasia and a recommendation for re-do biopsy was raised by pathologist ( Fig. 2 ). Fig. 1 Showing a segmental non circumferential polypoid mass pressing the mucosa with luminal narrowing but no mucosal ulceration. Fig. 1 Fig. 2 Initial colonoscopy biopsy results: A(×2) & B(×40): Hematoxylin and Eosin (H/E) showing fragments of colonic mucosa surfaced by columnar and goblet cells (black arrows). Fig. 2 Showing a segmental non circumferential polypoid mass pressing the mucosa with luminal narrowing but no mucosal ulceration. Initial colonoscopy biopsy results: A(×2) & B(×40): Hematoxylin and Eosin (H/E) showing fragments of colonic mucosa surfaced by columnar and goblet cells (black arrows). The abdominal CT scan done with both IV and rectal contrast to characterize the mass also it's relationship with other organs in preparation for multidisciplinary tumor (MDT) board discussion revealed a wall thickening about 4.5 cm long partially obstructing the lumen at rectosigmoid junction with no-suspicious lymph nodes ( Fig. 3 a–c). The patient was evaluated and managed at the Department of General Surgery, together with medical gastroenterology department. Resource limitations influenced the extent of preoperative investigations such as endoscopic ultrasound and decision for definitive surgical management such as laparoscopic exploration and excisional biopsy. Fig. 3 a: CT scan abdomen axial view with rectal and IV contrast showing a mass in rectosigmoid area with wall thickening, partially obstructing the lumen with contrast passing above the lesion (arrow). b; CT scan abdomen sagittal view with rectal and IV showing the mass (arrow). c: CT scan abdomen coronal view with rectal and IV contrast showing a mass in rectosigmoid area partially obscuring the lumen (arrow). Fig. 3 a: CT scan abdomen axial view with rectal and IV contrast showing a mass in rectosigmoid area with wall thickening, partially obstructing the lumen with contrast passing above the lesion (arrow). b; CT scan abdomen sagittal view with rectal and IV showing the mass (arrow). c: CT scan abdomen coronal view with rectal and IV contrast showing a mass in rectosigmoid area partially obscuring the lumen (arrow). The findings were discussed in MDT with inconclusive pathological findings, a consensus for re-do colonoscopy and biopsy was reached which again revealed same findings, and then a decision for exploratory laparotomy with segmental excision biopsy. Patient was then re-admitted and scheduled for elective planned procedure.

C.S: Study conception, data collection and production of initial manuscript. O.H: data collection, citations and discussion. M.N: medical gastroenterologist, colonoscopy findings. C.N; clinical pathologist. A.A: proofreading and case review. A.N: manuscript revision, proofreading and supervision.

Written informed consent was obtained from the patient for the publication of this case report and the accompanying images. A copy of the written consent is available for review by the corresponding author of this journal.

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Dr. Clarence Sumbizi, resident General surgery Aga khan medical college East Africa, Contact; [email protected] +255743578102 Dr Aidan Njau, senior consultant general and laparoscopic surgeon, Aga Khan Hospital Dar es Salaam. Contacts; [email protected] +255 754 310 407.

Sigmoid endometriosis is a rare but important cause of gastrointestinal symptoms in women, especially those with a history of gynecological disorders. This case highlights the importance of considering endometriosis in the differential diagnosis for women with chronic abdominal pain and cyclic gastrointestinal symptoms. Colonoscopy, imaging, and histopathological evaluation are key components in diagnosing this condition. Surgical resection, particularly laparoscopic resection, offers an effective treatment option, providing relief from symptoms and improving quality of life. Early diagnosis and individualized treatment strategies are essential to achieving the best possible outcomes for patients with sigmoid endometriosis.

Sigmoid endometriosis is rare and frequently misdiagnosed. Our patient experienced a 4-year history of symptoms that were initially overlooked. This highlights the critical role of thorough history-taking and symptom pattern recognition [ 15 ]. While gynecologic evaluations were normal, multidisciplinary assessment led to appropriate imaging and biopsy attempts. Imaging plays a critical role in the evaluation of suspected bowel endometriosis. Transvaginal ultrasound, endoscopic ultrasound and magnetic resonance imaging, particularly when performed by experienced operators, are reliable modalities for detecting deep infiltrating endometriosis, including involvement of the rectosigmoid colon [ 16 , 17 ]. Colonoscopy, although valuable in excluding malignancy, has a limited role in diagnosing endometriosis, as lesions are typically submucosal or serosal and may not be visible from the mucosal surface. Mucosal biopsies frequently yield nonspecific findings unless there is transmural involvement [ 18 ]. Histopathological evaluation is critical to distinguish between malignant and benign conditions, with endometriosis often requiring full-thickness excision through surgical resection, typically showing inflammatory changes and the presence of endometrial glands and stroma [ 11 ]. The initial colonoscopy in our patient revealed a polypoid mass, from which the mucosal biopsy was taken, showing only nonspecific inflammatory changes. A contrast-enhanced CT scan further demonstrated a partially obstructing lesion at the rectosigmoid junction. Given the inconclusive histopathology and persistent symptoms, the case was discussed in a multidisciplinary tumor board. Collaboration among general surgeons, gynecologists, gastroenterologists, radiologists, pathologists, and clinical oncologists was essential in reaching a consensus to proceed with exploratory laparotomy and segmental resection as discussed by Wolthuis et al. [ 8 ]. CT of the chest and brain MRI were not performed due to limited resources and low clinical suspicion for distant metastases given benign nature of initial CT scan and colonoscopy. Immunohistochemical staining for estrogen and progesterone receptors could not be performed due to lack of availability and insufficient tissue sample. Despite the mass size, deeper biopsy was not attempted due to its submucosal location and the associated risk of bowel perforation. The management of sigmoid endometriosis is often surgical, particularly in cases where the patient experiences significant symptoms such as chronic pain, bowel obstruction, or infertility. Surgical options include laparoscopic resection of the affected portion of the colon, which provides the advantage of reduced recovery time and fewer complications compared to open surgery [ 13 ]. Hormonal therapy, such as oral contraceptives, GnRH agonists, or progestins, can be used as an adjunct to surgery or as a primary treatment for smaller lesions or patients who are not candidates for surgery. Hormonal therapy works by suppressing ovarian function and reducing the growth of ectopic endometrial tissue [ 13 ]. In our case, surgical resection was chosen over hormonal therapy due to persistent symptoms, inconclusive biopsy results, and potential for obstruction. This approach aligns with the literature recommending surgery in symptomatic or obstructive bowel disease [ 13 ]. All in all, CT scan, endoscopic ultrasound, MRI, and colonoscopy can help guide the surgical decision-making process, while biopsy remains the gold standard for confirming the diagnosis [ 11 ]. However, in many cases, as was in ours, biopsies are limited to mucosal samples due to the high risk of perforation associated with attempting full-thickness biopsy during colonoscopy. Given the nature of endometriosis and its typical involvement of the deeper bowel layers, mucosal biopsies are unlikely to detect the disease. As a result, excisional biopsy through surgical resection remains the most reliable method for definitive diagnosis. Surgical resection can significantly improve quality of life by alleviating symptoms of pain and gastrointestinal disturbances. Nevertheless, recurrence is common, and patients may require further treatment, including hormonal therapy, to manage residual disease or prevent recurrence [ 12 ]. Our patient's diagnostic journey mirrors the challenges documented in published literature where sigmoid endometriosis mimics malignancy. For instance, the presentation as a large, stenotic lesion created a diagnostic dilemma with colorectal cancer, a recurring theme reported by authors like Dimoulios et al. [ 10 ]. Bong et al. [ 15 ] specifically discuss these “diagnostic ambiguities,” which arise because the disease is primarily submucosal, making superficial biopsies non-diagnostic [ 9 , 18 ]. Consequently, as in cases of bowel obstruction reported by Long-Zhi et al. [ 19 ], our management pathway was driven towards surgery. This case is therefore consistent with the body of evidence showing that when faced with an obstructing mass and inconclusive endoscopic findings, surgical resection becomes the necessary definitive diagnostic and therapeutic procedure.

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Endometriosis is a gynecological condition affecting approximately 10 % of reproductive-age women [ 1 , 2 ]. While typically involving the ovaries and pelvic peritoneum, bowel endometriosis, particularly involving the sigmoid colon, is rare and diagnostically challenging due to its nonspecific symptoms mimicking gastrointestinal disorders [ 3 ]. The most accepted theory is retrograde menstruation, though others include coelomic metaplasia and immune dysregulation. These mechanisms may explain the ectopic implantation of endometrial tissue on the bowel [ 4 , 5 ]. The clinical presentation of sigmoid endometriosis can be quite insidious. It typically manifests as cyclic abdominal pain associated with the menstrual cycle, accompanied by altered bowel habits, including diarrhea or constipation [ 6 ]. However, the symptoms are often non-specific, leading to misdiagnosis or delayed diagnosis. These symptoms are frequently dismissed as being related to other, more common gastrointestinal or gynecological conditions [ 7 ]. This diagnostic challenge is further compounded by the fact that traditional imaging methods, including ultrasound or CT scans, may fail to detect endometrial lesions on the colon or rectum, making endoscopy and colonoscopy essential for diagnosis [ 8 , 9 ]. Sigmoid endometriosis poses significant challenges in both diagnosis and management. Given that it mimics many gastrointestinal diseases, clinicians often overlook it in favor of more common diagnoses [ 10 ]. The lack of specific markers for endometriosis also contributes to its underdiagnosis. While gynecological evaluations often yield normal results in these patients, the presence of rectal involvement can be identified through imaging techniques like colonoscopy, which allows for direct visualization and biopsy. Histopathological examination of tissue samples remains the gold standard for confirming the diagnosis, often revealing inflammatory changes with endometrial glands and stroma consistent with endometriosis [ 11 ]. A key challenge in managing sigmoid endometriosis is the need for a multidisciplinary approach. The involvement of gynecologists, gastroenterologists, and surgeons is crucial to ensure comprehensive care and to rule out other potential causes of symptoms [ 12 ]. The treatment typically involves surgical resection of the affected tissue. In some cases, hormonal therapies such as oral contraceptives or GnRH agonists may be used adjunctively to control disease progression or in patients with contraindications to surgery [ 13 ]. The management of endometriosis-related gastrointestinal symptoms, however, remains complex, and surgical intervention is often required to alleviate pain, treat bowel obstruction, and improve overall quality of life. We present a case of sigmoid endometriosis highlighting the importance of a multidisciplinary approach, bringing together a team of general surgeons, gynecologists, pathologists, radiologists, gastroenterologists and clinical oncologists. This paper has been reported in line with the revised SCARE 2025 criteria [ 14 ].

CT scan computed tomography scan ERAS Enhanced recovery after surgery GnRH Gonadotropin Releasing Hormone IBD Inflammatory bowel disease IBS Inflammatory bowel syndrome MDT Multidisciplinary team MRI magnetic resonance imaging USS Ultrasound computed tomography scan Enhanced recovery after surgery Gonadotropin Releasing Hormone Inflammatory bowel disease Inflammatory bowel syndrome Multidisciplinary team magnetic resonance imaging Ultrasound

The authors declare that they have no competing interests.

Intra operative findings were a hard irregular mass at rectosigmoid junction 4 cm by 5 cm chocolate like ulcerative mass on the serosal side, but the rest of the intestine was healthy and no suspicious regional lymph nodes or other similar lesions upon further exploration, segmental resection was done with end-to-end stapled anastomosis ( Fig. 4 , Fig. 5 ). Fig. 4 Intra operative image showing a tumor with ulcerated serosal side “chocolate” like lesion. Fig. 4 Fig. 5 Showing surgical specimen after segmental excision. Fig. 5 Intra operative image showing a tumor with ulcerated serosal side “chocolate” like lesion. Showing surgical specimen after segmental excision. Post operative care was uneventful, according to ERAS protocol for colorectal surgeries, and patient was immediately ambulated within 24 h of surgery. She started oral sips 24 h operatively; she was discharged after 72 h with normal bowel habits. The final tissue diagnosis came to be colonic endometriosis ( Fig. 6 ) post operative follow up was done with both gynecologist and general surgeon. Fig. 6 a: Showing final excision biopsy results: C (×2): H/E sections show colon mucosa layer (blue arrows) surfaced by columnar and goblet cells, while at the deep muscularis propria layer showing nests of endometrial glands and stroma. D(×4) and E(×10): H/E sections shows nests of endometrial glands and stroma embedded within muscular layer of the colon. b: D: Gross image of the resected colon. E; Cut section of the resected colon showing a whitish lesion at the wall forming a polypoid mass (arrow) partially obstructing the lumen. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Fig. 6 a: Showing final excision biopsy results: C (×2): H/E sections show colon mucosa layer (blue arrows) surfaced by columnar and goblet cells, while at the deep muscularis propria layer showing nests of endometrial glands and stroma. D(×4) and E(×10): H/E sections shows nests of endometrial glands and stroma embedded within muscular layer of the colon. b: D: Gross image of the resected colon. E; Cut section of the resected colon showing a whitish lesion at the wall forming a polypoid mass (arrow) partially obstructing the lumen. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)