Rare variations in renal anatomy and blood supply: CT appearances and embryological background. A pictorial essay

Helical CT angiography is increasingly used for the evaluation of the kidne ys and the renal vessels. Knowledge of the potential variants in renal and renal vascular anatomy and of their appearances on helical CT are thus indi spensable for radiologists who perform and interpret such examinations. We report six cases of anatomic variants that we encountered in our tertiary r eferral centre over the past 5 years, during which time we have performed 4 850 helical CT angiograms, including 1432 renal artery examinations. These represent rarer anomalies in renal vascularization, most of which were asso ciated with renal malformations (horseshoe kidney with or without cortical torsion, renal malrotation, single kidney, and thoracic origin of a renal a rtery). We present the helical CT findings and discuss the possible embryol ogical mechanisms and the practical implications of these abnormalities for the radiologist.