With two to three weeks of obstruction, marked ureteral dilatation develops in the presence of relatively low intraluminal pressures. The low pressure and increasing dimensions primarily reflect alterations in intrarenal hemodynamics and the viscoelasticity of the ureteral wall, respectively. Associated with these changes, the ureteral muscle hypertrophies, and this is accompanied by an increase ability to contract, as evidenced by an increase in contractile force and stress. Despite muscle hypertrophy and increased contractility, the dilated ureter is less able to generate the contractile intraluminal pressure waves that are required for urine transport. This paradoxical decrease in intraluminal pressure with increasing contractile force and diameter is explained by the Laplace relationship which also provides a rationale for ureteral tapering. Ureteral tapering by decreasing diameter allows the obstructed ureter's ability to generate contractile forces to be translated into higher contractile intraluminal pressures which provide for more efficient urine transport.