Partial ureteric obstruction: a study of Doppler ultrasonography and diuretic renography in different grades and durations of obstruction.

OBJECTIVES

To study the changes in renal resistive index (RI) and renal function with time during different grades of partial unilateral ureteric obstruction, and to determine the correlation between the ultrasonographic and renographic findings.

MATERIALS AND METHODS

Ten dogs underwent right partial ureteric obstruction: grade 1 (mild) obstruction was applied in five dogs (group A) and grade 3 (moderate and severe) obstruction in the other five (group B). All dogs were assessed using excretory urography, diuretic renography with the calculation of half-time drainage (T 1/2) and bilateral renal Doppler ultrasonography before the experiment began, after one week of obstruction, and every 2 weeks during 8 weeks of obstruction.

RESULTS

In both groups, after the induction of right ureteric obstruction, there was a progressive decrease of effective renal plasma flow (ERPF) and a progressive increase of the RI of the right kidney at the end of the first and second weeks of obstruction, with an almost stable value thereafter. The decrease of ERPF and the increase of RI in the right kidney were correlated with the degree of obstruction. There was also a dramatic increase of T 1/2 of the right kidney that correlated with the degree of obstruction. Concomitantly, there was a significant compensatory increase of ERPF and a significant decrease of the RI of the left kidney in both groups. The compensatory increase in CRPF limited the loss in total ERPF in both groups. The contribution of obstructed kidney to the total ERPF was significantly reduced in both groups. At the end of the eighth week, taking all kidneys together, there was a statistically significant negative correlation between the ERPF and RI, and between ERPF and T 1/2 and a positive correlation between T 1/2 and RI.

CONCLUSIONS

Unilateral partial ureteric obstruction increased the RI and T 1/2 and decreased the ERPF of the corresponding kidney, together with a decrease of RI and an increase in ERPF of the contralateral kidney. The more severe the obstruction, the greater the increase in RI and T 1/2 and the decrease in ERPF. After the obstruction stabilized, RI and T 1/2 were positively correlated.