Role of diuretic radionuclide renography in the evaluation of unilateral ureteropelvic junction obstruction after pyeloplasty

The incidence of ureteropelvic junction obstruction (UPJO) is about 1 in 1000 newborns with a left sided predominance. UPJO is the most common cause of urinary tract obstruction in children. Boys outnumber girls in a ratio of 2:1. Diuretic renography has proved to be a reliable non invasive test for assessing obstruction and differential function of the kidneys and assessing improvement after surgical intervention. Objectives: To assess the improvement in function and drainage in post operative cases of UPJO after pyeloplasty using DRR. Materials and Methods: Retrospective analysis of diuretic renograms for the past 8 years were reviewed. Among 156 patients with UPJO, 33 patients had pre and post pyeloplasty renography. Study included 13 females and 20 males in the age group range of 3 months to 56 yrs with an average age of 16.1 yrs. 23 (69.7%) patients had left side UPJO. The median time at which post pyeloplasty scintigraphy was done was 2.5 months. Scintigraphy was done as per predefined protocol using 99mTc-EC with measurement of relative function (RF) of each kidney. Diuretic was given at 10 min of study. Improvement in relative function of the diseased kidney was taken as an increase in ≥5% in relative function of that kidney post operatively, and deterioration in relative function taken as a decrease in relative function by ≥ 5% post operatively. An increase or decrease in renal function of less than 5% is considered to be a non significant change in renal function. Results: Hydronephrosis is noted in all the patients. 22 cases had evidence of obstruction at PUJ in the pre op renogram, of whom 19(86%) showed relieved obstruction post op study. Remaining 3 cases showed persistent obstruction of which 2 showed deterioration in function. 11 cases had no evidence of obstruction, underwent pyeloplasty in which 2 showed improvement in function, 2 showed deterioration and remaining stable function. Among the 33 cases only 6 (18%) patients showed improvement in relative function of diseased kidney post pyeloplasty, 7 (21%) patients showed deterioration in renal function, whereas 20 (61%) showed stable renal function in post op scan. Conclusion: Our study suggests that 99mTc-EC renal scintigraphy plays a significant role in assessment of drainage and renal function, post pyeloplasty in UPJO patients. Our study shows that in most patients, post pyeloplasty the obstruction was relieved, but majority showed no significant improvement in renal function in diseased kidney post operatively done as early as 2 months. So for follow up for improvement in function DRR should be done more than 2 months after pyeloplasty