Percutaneous upper urinary tract dynamics in equivocal obstruction.

Percutaneous pressure flow studies in the upper urinary tract remain the definitive method of distinguishing stasis from obstruction. They are not technically difficult and the results of 2 large series show minimal, minor complication rates. The results in over 200 studies show that a clear-cut answer as to whether or not an obstruction is present is obtained in over 95% of patients, the remainder showing pressures in an equivocal range.