104 Unmasking Endometriosis: A Case of Refractory “Crohn’s Disease”

Endometriosis, defined as ectopic endometrial tissue outside the uterine cavity, involves the bowel in 5%–12% of cases. The rectosigmoid colon is most frequently affected, whereas ileal and cecal involvement are rare. Diagnostic confusion arises from clinical overlap with inflammatory bowel disease (IBD), as both can present with nonspecific symptoms such as abdominal pain, vomiting, diarrhea, and hematochezia. When endometrial lesions infiltrate the intestinal muscularis, obstructive symptoms may develop. We report a patient initially presumed to have refractory stricturing and penetrating Crohn’s ileitis, but ultimately found to have extensive small-bowel endometriosis causing obstruction and fistulization. Case Presentation: A 46-year-old woman presented with right-sided abdominal pain and partial small-bowel obstruction (SBO) at an outside community hospital. Imaging revealed terminal ileal stenosis, and she was diagnosed with presumed stricturing Crohn’s disease for which she received steroids and supportive care. Three months later, she was readmitted with recurrent SBO. Colonoscopy showed terminal ileitis, and vedolizumab was initiated. Despite advanced IBD therapy, she continued to experience obstructive symptoms. One year later, repeat colonoscopy again showed terminal ileitis, though biopsies were negative for active inflammation. Because of her ongoing symptoms, she was deemed to have failed vedolizumab. Over the following 3 years, adalimumab and ustekinumab were trialed with dose intensification, but she continued to have episodic abdominal pain, distension, and vomiting. Four years after her initial presentation, a CT enterography demonstrated persistent terminal ileal thickening, now with suspected entero-enteric fistula. Repeat colonoscopy showed submucosal nodularity at the appendiceal orifice and ileal narrowing with erythema. Ileal biopsies were negative for active inflammation or granulomas while colonic biopsies revealed mild chronic inactive colitis. She was referred to Penn State Carlino Family IBD Center for further management. Due to recurrent SBO despite multiple biologics, she underwent ileocecectomy with Kono-S anastomosis. Intraoperatively, stricturing disease was confirmed. Pathology, however, revealed extensive endometriosis infiltrating all intestinal wall layers. Immunohistochemistry was positive for PAX8, ER, and CD10, while negative for CDX2, excluding intestinal malignancy. She was referred to Gynecology for endometriosis management, and ustekinumab was discontinued.

This case highlights the diagnostic challenge of differentiating Crohn’s disease from small bowel endometriosis. Both conditions present with nonspecific gastrointestinal symptoms and can cause stricturing disease and intestinal obstruction. Endometriosis often spares the intestinal mucosa, leading to repeatedly negative colonoscopy biopsies, whereas Crohn’s classically reveal mucosal inflammation, ulceration and/or granulomas. Imaging modalities such as MRI and transvaginal sonography have utility in detecting pelvic and rectosigmoid endometriosis; however, small-bowel involvement sensitivity is limited. Definitive diagnosis is made by histopathology after surgical resection of the involved segments due to obstruction. Ileal endometriosis should be included as a differential diagnosis in women of reproductive age with recurrent SBO and treatment failure of multiple biologic agents with nondiagnostic colonoscopy biopsies. Multidisciplinary awareness and collaboration between gastroenterology, colorectal surgery, and gynecology is essential for accurate diagnosis of ileal endometriosis, and to tailor appropriate treatment plans.