Intussusception is uncommon in adults, with an incidence of only 0.15%, and when it does occur it is often due to organic cause such as malignancy or polyp. Endometriosis can involve the bowel, however it most commonly affects the sigmoid colon or rectum, and does not usually cause intussusception. Interestingly, very few cases of intussusception have been diagnosed preoperatively by endoscopy and even fewer cases with the lead point being endometriosis. We present a case of endometriosis causing ileocecal intussusception that was visualized by endoscopy prior to surgery. A 30 year old female presents to the ED with 1 month intermittent, inferior abdominal pain that is accompanied by bloating. She is passing gas and stool and has no fevers, chills, nausea or vomiting. She had hematochezia 6 months ago, but no blood in stool since that time and her LMP was 5 days prior. The patient's vitals are stable. Abdominal exam reveals moderate distention, normal bowel sounds, the abdomen is soft with mild tenderness in the right lower quadrant without rebound or guarding. Urine pregnancy test is negative; other labs were unremarkable. Pelvic US is negative. CT reveals concentric hyperdense rings (target sign) at the ileocecal junction with crescentic mesenteric fat (Figure 1). Endoscopy is performed revealing an erythematous, centrally opaque and ulcerated mass telescoping into the cecum at the ileocecal junction (Figure 2). The patient goes to the OR for a right hemicolectomy including terminal ileum, appendix and cecum, and an end-to-end anastomosis. On gross examination a 5.3x4.4x3.1cm white, rubbery transmural mass is found from the resected bowel involving the ileocecal wall and occluding the appendiceal orifice. Microscopic analysis reveals cecal endometriosis associated with focal transmural acute and chronic inflammation, edema and fibropurulent serositis. Two of eighteen lymph nodes have endometriosis. The patient recovers from the procedure and is discharged free of pain.Figure 1Figure 2There have been few cases of intussusception due to endometriosis, and in our literature review we were unable to find a case where the lesion was visualized on endoscopy. While imaging identified the sole lesion in our case, small lesions with can be missed. In adults, the cause for intussusception is often neoplastic and colonoscopy is a useful tool prior to surgery to examine if there are further less obvious lesions that may require the surgical plan to be modified.