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

This 13-year-old with Williams syndrome presented in urinary retention. After catheter bladder drainage for a few days, when the catheter was removed, he voided without problems for several weeks and then again went into urinary retention. VCUG showed a huge left bladder diverticulum and a smaller right diverticulum (Figure 1). The left diverticulum completely filled in the space between the back of the bladder and the sacrum (Figure 2). When he voided, he emptied his bladder completely and very rapidly, buy in three directions, out the urethra and into both diverticula. Neither diverticulum obstructed the urethra (Figure 3). There was no reflux. After voiding, the empty bladder (Figure 4) rapidly refilled with the contrast material from the diverticula as they emptied back into the bladder (Figure 5).

This is the phenomenon of "aberrant micturition." The bladder empties perfectly through the urethra, but it also empties in the wrong direction into the diverticula (or more commonly, into refluxing megaureters). This is the so-called megacystis-megaureter association, although in this boy, the diverticula take the place of the refluxing ureters.

Years of constant recycling of refluxed urine lead to bladder enlargement, eventual bladder wall thickening, and myogenic bladder failure. This is analagous to aortic insufficiency that leads to left ventricular enlargement, eventual left ventricular hypertrophy, and then heart failure. In the case of the heart, digitalis is helpful. In the case of the urinary bladder, a catheter rests the muscle and provides temporary improvement. The treatment, of course, is diverticulectomy. The bladder, in almost every case, returns to normal. Bladder diverticula are a common finding in patients with Williams syndrome. Other findings in Williams syndrome include hypercalcemia and aortic and other arterial stenoses.