Diagnosis of adult midgut malrotation in CT: sign of absent retromesenteric duodenum reliable.

objectivesTo compare the incidence of absent retromesenteric duodenum with other radiological signs and to assess its diagnostic significance for midgut malrotation in adults.

methodsThis IRB-approved retrospective single-center study involved adult patients who underwent abdominal CT scans. Patients were screened for the presence of the absent retromesenteric duodenum sign. Signs observed included the position of the duodenal-jejunal junction (DJJ) and jejunum within the abdomen, the relationship between the superior mesenteric artery (SMA) and superior mesenteric vein (SMV), the locations of the ascending colon, cecum, and appendix, and the presence of intestinal volvulus.

resultsA total of 5594 patients were included. Seven patients exhibited the sign of absent retromesenteric duodenum. Four of these patients were identified as those diagnosed with midgut malrotation in the past five years. The common features observed in all 11 patients were: the horizontal segment of the duodenum did not traverse behind the SMA but instead curved rightwards and forwards adjacent to it; the DJJ and jejunum were positioned in the right abdomen; the SMV was anterior to the SMA. In 7 patients (7/11), the ascending colon, cecum, and appendix were located in the left abdomen. 5 patients (5/11) showed a high cecum position, and 2 patients (2/11) exhibited a pelvic appendix.

conclusionThe absent retromesenteric duodenum sign in CT diagnosis of adult midgut malrotation has proven to be more reliable. CRITICAL RELEVANCE STATEMENT: Radiologists should routinely identify the course of the duodenum horizontal segment in CT images, to prevent misdiagnosis of adult midgut malrotation. KEY POINTS: CT is suitable for the diagnosis of adult midgut malrotation. Absent retromesenteric duodenum for diagnosing adult midgut malrotation is more reliable than other signs. Diagnostic CT criteria for adult midgut malrotation need updating.