Intestinal duplication diagnosed preoperatively with double-balloon enteroscopy: an extremely rare case report and literature review.

Gastrointestinal duplications are congenital malformations that are usually observed in pediatric patients. Diagnosis in adulthood is quite rare, and preoperative diagnosis of gastrointestinal duplication is difficult, particularly in the small intestine. We encountered an extremely rare adult case of duplication of the jejunum, which showed a stomach-like form diagnosed using double-balloon enteroscopy (DBE). The patient was an 18-year-old male who had been experiencing upper abdominal pain and vomiting repeatedly without any triggers for 3 years. Various examinations were performed, but no cause of symptoms was found. DBE revealed a narrow opening of the lumen at the upper jejunum, and the lumen was covered with mucosal folds similar to those of the stomach. Enteroclysis via DBE showed a tubular structure on the mesenteric side of the jejunum. We diagnosed a jejunal tubular duplication with ectopic gastric mucosa and underwent partial small bowel resection. The patient's abdominal symptoms resolved. From this, DBE can be a useful tool for diagnosing intestinal duplication in adults. We believe that this case and literature review will facilitate the accurate and prompt diagnosis of small intestinal duplication.