Duplex Kidney

This infant presented with urinary tract infection. The longitudinal ultrasound image of the right kidney above shows a dilated upper pole pelvicalyceal system and a non-dilated lower pole. The appearance is consistent with duplex collecting system with obstructed upper pole moeity.
The ureter draining the lower moeity typically has a normal insertion site at the trigone. The ureter draining the upper moeity typically has an ectopic insertion distal to the VUJ (bladder, urethra, or genital tract).
The ectopic ureter is prone to obstruction and the orthotopic ureter to vesicoureteric reflux. There may be a ureterocoele associated with the ectopic ureter, as there was in this case (not shown).
Reference: Dähnert W. Radiology Review Manual 5th edition. Lippincott, Williams & Wilkins 2003
Credit: Dr Laughlin Dawes
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