Rectosigmoid endometriosis as a diagnostic chameleon mimicking colorectal carcinoma

Abstract

Bowel endometriosis is an uncommon manifestation of endometriosis that can clinically and radiologically mimic 
colorectal malignancy. Because the disease predominantly involves the deeper layers of the bowel wall with relative sparing of the mucosa, endoscopic findings may be normal, posing a significant diagnostic challenge. A 38-year-old woman presented with abdominal distension, epigastric pain, vomiting, constipation, and loss of appetite for 3 months. Radiological imaging revealed circumferential wall thickening at the rectosigmoid junction with luminal narrowing and features suggestive of distal colonic obstruction suspicious for malignancy. Sigmoidoscopy demonstrated normal mucosa with the inability to negotiate the scope beyond the narrowing. Mucosal biopsy revealed chronic non-specific colitis. Due to persistent radiological suspicion of malignancy, surgical resection was performed. Histopathological examination demonstrated endometrial glands and stroma infiltrating the serosa, muscularis propria, and submucosa of the rectosigmoid colon, confirming the diagnosis of rectosigmoid endometriosis. Rectosigmoid endometriosis may closely mimic colorectal carcinoma on imaging, while endoscopic findings remain non-specific. Awareness of this diagnostic pitfall is essential in reproductive-age women presenting with colorectal obstruction to prevent misdiagnosis and unnecessary radical treatment.