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

This boy was three years old when he had his first urinary infection. He had fever and systemic illness. An ultrasound exam showed that the right kidney measured 7.3 cm in length and the left 6.0. This meant that the left kidney was smaller than expected. Usually the left kidney is the same size as the right or no more than 5mm larger. A voiding cystogram showed a bladder capacity of 700 ccs (predicted at this age is 150ccs). He had bilateral grade 4 reflux with a dysmorphic appearing left calyceal system (Figure 1). He had a large, smooth-walled bladder which emptied completely, although partially in the wrong direction (Figure 2). When the refluxed contrast material flowed back into the bladder, the bladder refilled again immediately with refluxed urine (Figure 3A,B). His urethra was normal. He underwent anti-reflux surgery and a recent voiding cystogram (he is now 6 years old), showed a bladder capacity of 450 ccs (the predicted capacity for a boy of this age is 240 ccs). This is an example of the so-called megacystis / megaureter association. That is , there is a large, smooth, thin-walled bladder that occures as a result of the constant recycling of refluxed urine. The bladder returns to a more normal capacity after the reflux is corrected.