eP249 - Large Bowel Obstruction: Malignancy vs Endometriosis, Which Is the Culprit?

Purpose/Background: The differential diagnosis for large bowel obstruction (LBO) is broad, ranging from benign to malignant causes, and less commonly can include other organ systems. Endometriosis is an unusual cause of LBO that mimics common clinical and radiographic findings of colorectal cancer. The differential diagnosis for a patient presenting with a LBO needs to remain broad with subsequent workup thorough to evaluate for all potential causes, including alternative diagnoses, even with an initial high suspicion of malignancy.Methods/Interventions: We present a 37-year-old female with a history of diverticulitis who presented with abdominal pain, loose stools, blood per rectum, and recent 50-pound weight loss. A CT abdomen/pelvis was performed demonstrating an obstructing mass in the sigmoid colon. Subsequent colonoscopy was unsuccessful at traversing the luminal obstruction. Biopsies returned as colonic mucosa with patchy edema, fibrosis, glandular distortion, and mild mixed inflammation. A high suspicion for colonic malignancy remained, and given the concern for impending obstruction, the patient was taken to the operating room for laparoscopic sigmoidectomy. Intraoperative findings were consistent with tissue changes expected for colon cancer. Unexpectedly, final pathology returned as endometriosis with associated inflammatory mucosal changes, negative for dysplasia and malignancy.Results/Outcomes: The lack of evidence of Endometriosis, from initial workup through intraoperative resection, led to a surprising discovery of endometrial tissue on pathology. Our patient had no prior episodes of endometriosis, characteristic “power burn” lesions were not present, and there was no extraluminal involvement. In hindsight, initial findings of fibrosis without malignancy on colonoscopy biopsy may have alluded to the diagnosis of deep bowel endometriosis secondary to repeated tissue injury and repair, as opposed to colon cancer. Additionally, radiographic adjuncts including MRI imaging may have been useful in identifying rectal wall thickening, commonly seen in bowel endometriosis, which would have aided in identifying the lesion-to-anal-verge distance (LAVD) for surgical planning of the rectosigmoid endometriotic lesion.Conclusion/

Discussion: Bowel endometriosis is a viable differential diagnosis in the setting of large bowel obstruction and should be included to allow for improved patient outcomes with appropriate preoperative medical and radiographic workup, especially in the case of women of child-bearing age. In our patient, colon resection was inevitable due to the obstructive nature of endometriosis, but in different situations, medical management, additional CT/MRI imaging, shaving, or disc excision may be more appropriate.Sagittal CT Scan Persistent focal mucosal thickening of the distal-mid sigmoid colon with subtle adjacent inflammatory changes