Prearterial reversed midgut rotation. A rare congenital anomaly.

A patient with a right-sided descending colon, left-sided ascending colon, and transverse colon in front of the superior mesenteric artery is described. We believe that this is only the second case of "prearterial" reversed midgut rotation existing with normally situated stomach and liver. The best explanation for these relationships seems to be (a) anomalous positioning of the primitive midgut-hindgut junction right of midline; (b) ensuing midgut rotation in a reversed, or clockwise, direction.