Evaluation of supernumerary kidney with fusion using magnetic resonance image.

Urogenital anomalies are frequent and correspond to 33% of all congenital anomalies (1). Horseshoe kidney and renal crossed ectopy with fusion are the most frequent renal anomalies (2). Supernumerary kidney is the rarest renal anomaly and it can be encapsulated or totally apart from the original kidney or connected to it by a sheath of connective tissue. Usually the supernumerary kidney is located caudally to the kidney of the same side and is associated with bifid ureter or more infrequently a double ureter (2,3). There are several reports of supernumerary kidney with fusion (2) but this is the first one described in the literature evaluated with magnetic resonance image. A female patient of 27 years old presented with left flank pain 3 days duration, dysuria and fever (100oF). Physical exam of abdomen was inconclusive and ultrasound suggested left duplication of the renal pelvis. Urine exam suggested urinary infection. After the administration of sedatives and antibiotics the patient was submitted to magnetic resonance image (MRI) of abdomen and pelvis (1.5T system GE Signa Excite). T1 and T2 weighted preand post-gadolinium enhancement were obtained. MRI showed a left moety fused to the upper pole of the supernumerary kidney (Figure-1). The supernumerary kidney showed a defect of rotation and had no dilation of the collecting system. The MRI also showed the presence of individual ureters (Figure-2). After the clinical treatment, the patient got better and was discharged. There are several theories to explain the occurrence of a supernumerary kidney: a) bifurcation of the ureteral bud with independent penetration of the buds in the metanephrogenic blastema that develop and divide in two kidneys; b) two independent ureteral buds that penetrate the metanephrogenic blastema that divides in two and c) fragmentation of the metanephrogenic blastema due to linear infarcts (3). The supernumerary Evaluation of supernumerary kidney with fusion using magnetic resonance image _______________________________________________