Summary. Stomach and duodenum ulcer occupies a leading place among the surgical diseases of the digestive organs (6–10 % of the population). Operated stomach diseases can be occurred in operated patients as a complication of resections (up to 35 % of cases), and often requires timely diagnosis and repeated invasive reconstructions of the gastrointestinal tract. The aim of the research is to present a clinical case of patient with an atypical course of the operated stomach disease and to highlight the main stages of the diagnostic and treatment algorithm. Materials and methods. Analysis of medical publications for the last 5 years, devoted to the clinic, diagnosis and treatment of the operated stomach disease, and analysis of a clinical case of a patient with a rare complication of this pathology. Results and discussion. The presented patient underwent Billroth II stomach resection for duodenum peptic ulcer in 2016. In 2021, a left chest wall fistula with suppuration appeared. According to the examination in the hospital (contrast fistulography followed by fibroesophagogastroscopy), the penetration of the stomach stump peptic ulcer into the left costal rib arch with the formation of an external gastric fistula was discover. The patient was operated on using «Laparotomy, stomach resection followed by end-to-end gastroenteroanastomosis reconstruction, Roux entero-enteroanastomosis» with simultaneous excision of the left costal rib arch fistula. In the postoperative period, the wounds healed per prima. The patient was discharged in satisfactory condition. Conclusions. The presented case is a casuistic rare complication of the operated stomach disease. Contrast fistulography followed by fibroesophagogastroscopy is useful to establish the cause of the fistula, which is an indication for repeated reconstructive surgery on the stomach stump and gastroenteroanastomosis with excision of the rib arch fistula. To prevent this complication, we recommend scheduled fibroesophagogastroscopy once a year.