Posteriorly situated retroperitoneal colon: A study using CT and MRI

Abstract

In a patient with symptoms attributable to lumbar spine disease, computed tomography (CT) demonstrated the descending colon lying in an exceptionally posteromedial position. The colon, within the retroperitoneal fat, passed between the psoas major and quadratus lumborum muscles, thereby abutting the normal left L4 ventral ramus lateral to the L5 pedicle. Although it remains debatable whether this curious anatomical arrangement was responsible for this patient's symptoms, the case prompted us to see how often the colon was situated so posteromedially. Among 33 consecutive patients whose abdominal CT images were analyzed, this close anatomical relationship was seen in only one patient; it was not seen in any of 50 randomly selected patients undergoing magnetic resonance imaging (MRI) of the lumbar spine. As judged by CT measurements, the average position of the most posteromedial portion of the descending colon lies 5 mm anterolateral to a plane joining the anterolateral margins of the psoas major, quadratus lumborum, and iliacus muscles and 54 mm from the ventral ramus. 0 1993 Wiley-Liss, Inc.