PARTIAL URETERAL OBSTRUCTION - ROLE OF RENAL RESISTIVE INDEX IN STAGES OF OBSTRUCTION AND RELEASE

Objectives. To study the changes in renal resistive index (RI) and ren al function before and after release of different grades of partial un ilateral ureteral obstructions. Methods. Ten dogs were subjected to ri ght partial ureteral obstruction. Grade 1 (mild) obstruction was appli ed to 5 dogs (group A) and grade 5 (moderate and severe) obstruction w as applied to the other 5 dogs (group B). Obstruction was maintained f or 8 weeks, followed by release of obstruction. All dogs were subjecte d to excretory urography, technetium-99m mercaptoacetyltriglycine diur etic renography with calculation of half-time drainage (T-1/2), and bi lateral renal Doppler ultrasonography before the start of the experime nt, after 8 weeks of obstruction, and every 2 weeks during the 8 weeks after release of obstruction. Results. In both groups, after inductio n of right ureteral obstruction, there was a dramatic decrease of effe ctive renal plasma flow (ERPF), increase of RI, and increase of T-1/2 Of the right kidney. Relief of obstruction was associated with normali zation of T-1/2, reversal of RI, and recovery of ERPF to near basal va lues. No correlation was found between ERPF at the end of the recovery period and the functional parameters (T-1/2, RI, or ERPF) of the obst ructed kidney before release of obstruction. Conclusions. (1) Unilater al partial ureteral obstruction produces an elevation of RI and T-1/2 and a fall in ERPF of the corresponding kidney. (2) After relief of ob struction, renal function is regained with associated reversal of RI. (3) Functional parameters (T-1/2, RI, or ERPF) of the obstructed kidne y do not predict the recovery of ERPF after release of obstruction. (4 ) Rapid reversal of a previously elevated RI is an early indicator of recoverability of renal function after relief of ureteral obstruction. (C) 1997, Elsevier Science Inc. All rights reserved.