Robert L. Lebowitz, M.D. Children' s Hospital, Harvard Medical School Boston, Massachusetts

Voiding cystogram showed bilateral lower pole reflux(Figure 1). The axis of each collecting system points toward the ipsilateral shoulder. The ureteropelvic junctions are medial.

This baby was found to have right hydronephrosis in utero. VCUG at two months of age showed reflux into both halves of a horseshoe kidney. The axis of each collecting system points toward the ipsilateral shoulder just as in lower pole reflux(Figure 2). However, the ureteropelvic junctions are anterior, not medial, and this is the clue that distinguishes reflux into a horseshoe kidney from reflux into the lower poles. A MAG-3 renal scan (posterior view) showed the isthmus of the horseshoe kidney(Figure3).