Adult Descending Colon Duplication Mimicking Colon Cancer: A Rare Case Report

Intestinal duplication is a rare congenital anomaly characterized by the presence of a segment of intestinal tissue containing both mucosal and muscular layers adjacent to the normal alimentary tract. Intestinal duplication is most commonly diagnosed in infancy and is rarely observed in adults. Colonic duplications are particularly uncommon and may be difficult to distinguish from malignancy. Herein, we report a rare case of an adult descending colon duplication that was suspected preoperatively to be colon cancer.

A 75-year-old man with a history of surgery for prostate cancer and a left inguinal hernia was referred to our department of gastroenterological surgery. Preoperative abdominal CT revealed a circumferential mass in the descending colon. Colonoscopy revealed a circumferentially elevated lesion approximately 30 cm from the anal verge with luminal narrowing that prevented scope passage. A biopsy revealed no malignancy. Owing to intestinal stenosis caused by the mass and suspicion of malignancy, we performed a laparoscopic left hemicolectomy with D3 lymph node dissection. Intraoperatively, the mass was adhered to 4 segments of the small intestine, necessitating partial small bowel resection. Histopathological examination revealed a tubular structure on the serosal side of the native colon lined with colonic-type mucosa and possessing its own muscularis propria, continuous with the normal colonic wall. These findings were consistent with intestinal duplication. The postoperative course was uneventful, and the patient was discharged on the 13th POD. No recurrence was detected on follow-up CT at 18 months postoperatively.

Colonic duplication in adults is extremely rare and may mimic colorectal carcinoma on imaging and endoscopy. Surgical resection provides both definitive diagnosis and curative treatment.