A case of cancer of the ampulla of Vater accompanied by malrotation.

Intestinal malrotation is caused by a developmental anomaly of the embryonic intestine. Most cases develop in neonates, and development in adulthood is rare and difficult to diagnose before surgery. Pancreaticoduodenectomy was performed for cancer of the ampulla of Vater accompanied by incomplete fixation in a 63-year-old male patient. A branch of the superior mesenteric artery was present on the resection line and was deemed likely to cause circulatory disorder in the small intestine, and the duodenum and jejunum were covered with a membranous structure making dissection, anatomical identification, and jejunectomy difficult. Herein, we report the case with a review of the literature.