ABSTRACT
Abnormal cephalad migration of the kidney is thought to occur in approximately 1 : 1000 people, with equal sex distribution, according to autopsy studies. Ectopic kidneys are found in the following locations: pelvic, iliac, crossed fused and thoracic. The ectopic kidney is often small, lobulated and abnormally rotated. In combination with abnormal vasculature, there is a higher risk of pelviureteric junction obstruction. A horseshoe kidney is the commonest renal fusion anomaly. The kidneys are joined by an isthmus which connects the lower poles in 95% of cases. Vesicoureteral reflux in the presence of horseshoe kidney has been documented in around 80%. A similar proportion of patients have associated heart, skeletal and neurological anomalies. The left kidney migrates to the right side three times more than the converse. The majority of cross renal ectopias are fused (85%), and the fusion occurs to the lower pole of the native kidney. The majority of cross-fused ectopias are asymptomatic and remain undetected.
