Upper urinary tract compliance: its importance in obstructive hydronephrosis.

Abstract

Improvements in diagnostic modalities over the last 15 years have meant that obstruction can now be diagnosed accurately in dilated upper tracts. However, it is no longer sufficient to diagnose obstruction in a hydronephrotic kidney; it is necessary to determine the likelihood of functional deterioration in that kidney by measuring its elastic distensibility (compliance). 111 pressure flow studies have been reviewed in an attempt to measure the compliance of each upper tract under study and to assess its clinical implications. Good compliance was seen in 64 dynamically unobstructed renal units as well as in 16 obstructed systems. These 16 obstructed systems with good compliance had less significant degrees of obstruction than a group of 31 obstructed systems with poor compliance. Obstruction with good compliance was associated with preservation of renal function as measured by diuresis renography whilst impaired function was seen in systems with obstruction and poor compliance. Systems with good compliance and obstruction may not necessarily need surgery to relieve obstruction but instead could be managed by avoiding a high fluid intake which is liable to produce a pressure rise in the kidney. Poor compliance or functional deterioration are indications for immediate relief of the obstruction.