Whitaker revisited.

Perfusion studies of the upper urinary tract have been associated (in our hands) with poor reproducibility during repeated studies carried out at the same sitting. In an attempt to overcome this, a fundamental modification of the Whitaker technique has been devised whereby, instead of measuring renal pelvis pressure during constant flow infusion, the flow rate has been measured during constant pressure infusion. The 2 techniques have been compared in a study carried out in normal ureters in anaesthetised dogs. The modified technique not only dispenses with the sophisticated equipment required for this test, but gives results which are more reproducible. In addition, it was noted that the modified technique allowed greater flow rates for given pressure measurements than was possible with the standard Whitaker test. It is thought that these findings are related to the effects of motor-driven syringe pumps, difficulty in data interpretation in some cases with Whitaker's test, and the stretch response of ureteric smooth muscle which may be excessively stimulated during the Whitaker test.