The sonographic evaluation of hydronephrosis with progressive ureteric obstruction. An experimental model.

An experimental animal model was set up to examine the interrelationship between urine flow and progressive ureteric stenosis in producing sonographically detectable hydronephrosis. In four rabbits with mild ureteric stenosis or no stenosis the renal pelvis showed little distension even with rapid diuresis. Progressively tighter ureteric stenoses resulted in progressive renal pelvic distension accentuated by diuresis. The implication is that the normal, unobstructed ureter in the rabbit is able to remove urine from the kidney as fast as it may be produced, even during conditions of maximal diuresis. Therefore, in the absence of any other factor that may contribute to overdistension of the upper urinary tract, a state of diuresis will not simulate hydronephrosis.