The retrorenal colon on computed tomography: a normal variant.

In a review of 200 patients, the position of the colon in relation to the posterior aspect of the kidneys on CT was studied. A small part of the colon was found in the left retrorenal position in 1.0% of the patients. An illustrative case report of an unusual colonic variation in which the colon coursed directly behind the kidneys is described. The anatomy of the retroperitoneal fascia and the significance of the retrorenal colon are discussed.