Interposition of the colon between the kidney and the psoas muscle: a normal anatomic variation studied by CT.

The position of the bowel in the pararenal space was examined in relation to the kidney and the psoas muscle in 1203 abdominal computed tomographic (CT) examinations. The ascending colon was found between the lower kidney pole and the psoas muscle in 1.7% and the descending colon in 0.7% of the patients. This variation appeared more frequently in women, young adults, and individuals with less intrabdominal fat. Lateral displacement of the lower kidney pole was observed in 40% of the patients with this normal variation. These findings may be of value when interpreting urographic and abdominal CT examinations.