1525 Atypical Presentation of Colon Cancer: Colon-Vaginal Fistula

Abstract

INTRODUCTION: A fistula is an abnormal communication between two epithelialized surfaces. Colovaginal fistulas usually present with stool or flatus per vagina, foul-smelling vaginitis resistant to treatment, previous hysterectomy, and history of diverticulitis. In this case report, we present colon cancer as a possible new risk factor for colo-vaginal fistula. CASE DESCRIPTION/METHODS: 53 years old female with a past medical history of external hemorrhoids and GERD presented to the emergency department (ED) for evaluation of right lower quadrant abdominal pain for over a month associated with passing fecal material through her vagina for the past 2 days. The patient also reported having loose stools approximately 2 weeks prior to ED visit. She also reported decreased appetite, lightheadedness, 60 lb weight loss since last year, and significant rectal bleeding with straining which she attributed to hemorrhoids. She reported having an unremarkable colonoscopy 10 years prior to presentation. She denied any history of diverticulosis, ulcerative colitis, Chron's disease, radiation therapy, or family history of cancer. However, she did have a history of hysterectomy for the treatment of endometriosis 15 years ago. On arrival, she was found to have a hemoglobin of 5.4 g/dl. Physical exam was significant for pale mucous membranes, tachycardia, and fecal material in the vaginal canal. CT scan showed a ring-enhancing fluid collection interspersed between the vaginal cuff, and sigmoid colonic bowel loop, a colovaginal fistula between the vaginal cuff and the sigmoid colon, and wall thickening of the sigmoid colon measuring up to 1.5 cm. Colonoscopy showed a large friable obstructive mass seen at 20 cm from the anal verge. Biopsies of the sigmoid mass showed invasive, moderately differentiated adenocarcinoma. DISCUSSION: This patient has a history of total abdominal hysterectomy which is a known risk factor for the development of fistula; however, the hysterectomy was done 15 years before the appearance of the fistula, suggesting that the surgical procedure was not the primary cause of the development of the fistula. Inflammatory bowel disease and infectious process were ruled out by colonoscopic and histologic findings. From this case, we can learn that colon cancer can mimic other conditions such as Crohn's disease or complicated infectious process, therefore colon cancer should be part of the differential diagnosis of colo-vaginal fistulas and peri-colonic abscesses.