In children, duodenal fistulas are often formed against the background of foreign bodies of the gastrointestinal tract (nails and magnetic balls), rarely congenital fistulas. A patient aged 7 years and 9 months was treated for a duodenal fistula in surgical department no. 3 of the clinical hospital of St. Petersburg State Pediatric Medical University. The patient has had repeated vomiting and loose stools since 2023, which were interpreted as an intestinal infection. An overview X-ray of the abdominal organs revealed two X-ray contrast foreign bodies, presumably batteries. In obtaining additional medical history, it was found that the child swallowed the batteries in the presence of his parents on March 3, 2024. In dynamics, after 3 days, the foreign bodies left the patient’s gastrointestinal tract naturally. A long-term, multicomponent examination showed a small-colonic fistula. Further, the EGD with X-ray navigation revealed that the small-colonic fistula was a duodenum-rim fistula. Laparoscopic separation and suturing of the duodenum-rim fistula was performed using a stitching device. After the surgical treatment, clinical improvements were noted: the child’s appetite improved, the patient gained approximately 1 kilogram in weight, the patient’s stool became decorated up to 2–3 times a day, and vomiting did not repeat. Additionally, control ultrasound of the abdominal cavity displayed no pathology. The patient was discharged in satisfactory condition under the supervision of a pediatric surgeon and gastroenterologist at her place of residence. Duodenal fistulas are diagnosed using imaging research methods. The most appropriate method is an X-ray contrast examination of the gastrointestinal tract, which can show the fistula and its extent and localization. Moreover, endoscopic fistulography is an effective diagnostic method. Surgical treatment of duodenal fistulas can be open or laparoscopic. In the current study, the duodenal fistula was probably congenital in nature. However, considering the neurological status and concomitant disease of the child, it can be assumed that the formation of a fistula was caused by ingestion of magnetic foreign bodies.