BACKGROUND Anastomotic failure after gastroenterological surgery is usually treated by intraperitoneal drainage and a mature ductal fistula. A ductal fistula may develop into a labial fistula. Although a ductal fistula is controllable, a labial fistula is intractable. We report a case of a labial fistula that communicated with the duodenal stump after gastrectomy. This condition was successfully treated by intraluminal drainage with continuous suction (IDCS) via a rectus abdominis musculocutaneous flap (RAMF). CASE REPORT A 70-year-old male underwent distal gastrectomy with intentional lymphadenectomy because of advanced gastric cancer. Digestive reconstruction was completed by the Billroth II method. Pancreatic leakage, intraperitoneal abscess, and anastomotic failure of gastrojejunostomy occurred after surgery. The duodenal stump was ruptured at postoperative day (POD) 26, and ductal fistula associated with the duodenum was observed. Unfortunately, this ductal fistula developed into a labial fistula at POD 90, and a high output of duodenal juice was observed. Additional surgery was proposed at POD 161. The broken stump and labial fistula were covered by a pedunculated RAMF, and a dual drainage system (a combination of a Penrose drain and a 2-way tube) travelled through the RAMF. The tip position of the drainage system was located in the duodenum, and the IDCS was effectively introduced. The secondary ductal fistula finally matured through the RAMF, and was subsequently closed at POD 231. The intractable labial fistula was successfully treated, and the patient was discharged at POD 235. CONCLUSIONS A high-output labial fistula, which communicated with the duodenal stump after gastrectomy, was refractory in our patient. Effective IDCS through an RAMF was useful for replacement of the labial fistula with a secondary ductal fistula.