ABSTRACT
Horseshoe kidney malformation is the most common congenital renal anomaly and has an incidence of 0.25% (1:400 live births).1 As with other fusion anomalies, it is more common in males, with a 2:1 ratio. The etiology likely involves abnormal migration of the metanephric blastema toward the midline with consequent communication and fusion of the lower poles. The tissue that connects both poles, the isthmus, is bulky and usually parenchymal. The isthmus prevents cranial migration of the mid-portion of the renal mass superior to the inferior mesenteric artery, and the kidney does not complete its normal rotation. The pelvis is positioned anteriorly and the ureters cross ventral to the isthmus.
