Comparison of two drainage parameters on diuretic renogram in predicting the fate of prenatally detected pelvi-ureteric junction-like obstruction.

INTRODUCTION

In infants with suspected pelviureteric junction (PUJ) like obstruction, we compared the drainage patterns suggested by t 1/2 and normalized residual activity (NORA) to determine which parameter can differentiate obstructive from nonobstructive dilatation and thus predict the need for surgery.

MATERIALS AND METHODS

Infants presenting with prenatally detected PUJ-like obstruction from January 2014 to March 2020 were evaluated with ultrasonography. Diuretic renogram was performed using Tc99m ethylene dicysteine using the F0 protocol. Subjects with a differential renal function >40% were included in the study. The t ½ values were noted. NORA was calculated by dividing the tracer values at 60 min with the values at 2 min. The infants were followed using ultrasonography. Renogram was repeated if there was increase in hydronephrosis or after 6 months if hydronephrosis did not regress. The follow-up was continued till a decision for pyeloplasty was made or the hydronephrosis regressed. Pyeloplasty was advised if differential function dropped to below 40%.

RESULTS

34 patients met the inclusion criteria. NORA and t ½ had very poor concordance in defining the drainage pattern. t ½ values did not correlate with the need for surgery or conservative management ( ≥ 0.05). Good drainage pattern by NORA was associated with regression of hydronephrosis ( ≤ 0.001). NORA predicted obstruction more accurately.

CONCLUSION

NORA can define good drainage in a much larger subset of patients with PUJ-like obstruction who eventually do not need surgery. However, further multicenter studies are needed to confirm this.