Radiologic anatomy of the superior mesenteric vein and branching patterns of the first jejunal trunk: evaluation using multi-detector row CT venography.

The purpose of this study was to describe radiologic anatomy of the superior mesenteric vein (SMV) and to evaluate branching patterns of the first jejunal trunk on axial CT images and multi-detector row CT (MDCT) venography in adults. Two hundred and twenty consecutive patients who underwent abdominal CT examinations were enrolled in this study. Appearance of the SMV, branching patterns of the first jejunal trunk, and drainage site of the inferior mesenteric vein (IMV) were assessed on axial CT images and MDCT venography. The SMV and first jejunal trunk were identified in all patients. A single trunk of the SMV was present in 95% (210/220) and absent in 5% (10/220). First jejunal trunk crossed dorsal to the superior mesenteric artery (SMA) towards the left abdomen in 64% (141/220) and first jejunal trunk crossed ventral to the SMA in 19% (41/220). First jejunal trunk crossed dorsal to the SMA and abruptly turned towards the right abdomen in 17% (38/220). Among these 38 patients, biliary-enteric bypass surgery (n = 9) and large hematoma in left abdomen (n = 1) were present. The IMV was identified in 213 patients and was observed to drain into splenic vein in 112 patients (53%), SMV in 67 (31%), splenoportal confluence in 26 (12%), and first jejunal trunk in 8 (4%). In conclusion, the first jejunal trunk, abruptly turning toward the right abdomen, may be an anatomic variant or indirect finding of biliary-enteric anastomosis. The IMV may drain into the first jejunal trunk as well as splenic vein, splenoportal confluence, and SMV.