Relative renal function does not improve after relieving chronic renal obstruction

Abstract

Study Type - Therapy (case series) Level of Evidence 4. What's known on the subject? and What does the study add? Technetium-99m MAG3 renography can be used to quantify relative renal function (RRF). Deterioration of renal function occurs with chronic obstruction. Small studies have previously shown that RRF is not improved in adult patients after pyeloplasty. Some studies have suggested that patients with higher preoperative RRF are more likely to improve. To our knowledge, these data represent the largest review of cases related to this subject. This study verifies past studies' assertions that RRF does not improve after relief of chronic renal obstruction. Using multivariable analysis, we identify lower age and lower preoperative RRF as predictors of >7% improvement in RRF. These data suggest that the aim of relieving obstruction should be to maintain RRF and alleviate symptoms, but not to seek improvement in overall renal function. To determine the change in relative renal function (RRF) after relief of chronic obstruction in adults. We retrospectively identified 85 adult patients who underwent scintigraphic diuretic renography before and after an intervention to relieve chronic unilateral renal obstruction. Patients were stratified into groups of low (<20%), medium (20-40%) and high (>40%) preoperative RRF in the obstructed kidney. Each group was assessed for change in RRF after relief of obstruction. We performed multivariable logistic regression analysis to determine whether age and pre-procedural RRF predicted a >7% improvement in RRF, controlling for medical comorbidities and type of obstruction. The mean (sd) patient age was 43.6 (16.8) years and 66% of patients were female. The mean (sd) pre- and postoperative RRF values were not significantly different (37.6 [12.3] % vs 38.4 [13.6] %; P = 0.31). Patients stratified by low, medium and high preoperative function showed no significant change in postoperative RRF (P = 0.53, 0.39 and 0.77, respectively). In multivariable logistic regression analysis, younger age (odds ratio [OR] 0.90, 95% confidence interval [CI] 0.83-0.98) and lower preoperative RRF (OR 0.90, 95% CI 0.83-0.97) predicted improvement in RRF of >7%, after adjustment. RRF does not significantly increase after relief of chronic obstruction. The goals of relieving chronic renal obstruction should be to maintain renal function and relieve symptoms, but not to regain renal function.