RESUMEN
OBJECTIVES: To study the methods of prediction of recoverability of renal function after the treatment of adult patients with unilateral obstructive uropathy and a normal contralateral kidney. METHODS: This prospective study included 91 consecutive adult patients with the diagnosis of unilateral obstructive uropathy and a normal contralateral kidney. All patients had a nonequivocal cause of obstruction that was successfully relieved after treatment. All patients underwent plain abdominal x-ray, gray-scale ultrasonography, Doppler ultrasonography, excretory urography, and technetium-99m-diethylenetriamine pentaacetic acid radioisotope renography before and after treatment. Patients were seen regularly at 3, 6, and 12 months for a mean duration of 13 +/- 6 months (range 6 to 36). At each visit, ultrasonography and renography were performed, and excretory urography was performed at least once during follow-up. Several renographic and ultrasound parameters were studied before and after treatment to evaluate their value in predicting the recoverability of renal function. The difference between the selective renographic glomerular filtration rate (GFR) of the ipsilateral kidney before treatment and its mean value after treatment was considered as the reference variable to which all other variables were compared. All prognostic parameters were evaluated by both univariate and multivariate analyses. RESULTS: On univariate analysis, the factors that significantly affected the recoverability of renal function after the relief of obstruction included preoperative renographic GFR, renal perfusion, parenchymal thickness, parenchymal echogenicity, corticomedullary differentiation, reduction of the renal resistive index of the corresponding kidney, and compensatory hypertrophy of the contralateral normal kidney. However, using multivariate analysis, only the preoperative selective renographic GFR and renal perfusion of the corresponding kidney sustained their statistical significance as independent factors affecting renal functional recovery. A preoperative GFR value of 10 mL/min/1.73 m2 was estimated as the cutoff point that can determine the best prediction of stabilization or improvement of renal function after the relief of obstruction. CONCLUSIONS: Preoperative renographic clearance and perfusion of the corresponding kidney were the only predictors of recoverability of unilateral renal obstruction. Kidneys with a renographic GFR of less than 10 mL/min/1.73 m2 were irreversibly damaged. Improvement or stabilization of function can be expected after relief of obstruction of kidneys with a renographic GFR of 10 mL/min/1.73 m2 or greater.