Abstract
A 52-year-old female patient diagnosed with an adenocarcinoma of the sigmoid colon underwent anterior resection with direct anastomosis. Intraoperatively, we found the ileum completely retroperitonealized. Previously, the patient was asymptomatic and no congenital syndromes were diagnosed. The intraoperative finding of abnormal anatomy made the mobilization of the left hemicolon and the vessel ligation more challenging. This anatomical situation is a rare variation due to an embryonic malrotation, which occurs in about 1:500 newborns.