Low dose computed tomography-Kidney Ureter Bladder Follow Up in Post Retrograde Intrarenal Surgery Patients for Stone Clearance

Abstract

Introduction: To evaluate stone free rate (SFR) with low dose computed tomography-Kidney Ureter Bladder (CT-KUB) after retrograde intrarenal surgery (RIRS) and compare the relation of stone clearance with stone volume and Hounsfield Unit (HU). Materials and

Methods: The prospective observational study was conducted in Bir Hospital from January 2019 to January 2020 . A total of 42 patient with renal stone up to 20 mm size included. Lithotripsy was performed using Holmium laser utilizing High frequency Low Power Energy (HiFr- LoPE). Stone clearance was reassessed using low dose CT KUB at 1 month who were stone free on X-ray and ultrasound scan at 2 weeks. Patients were categorized as complete stone free, clinically insignificant Residual Fragment (CIRF) <4 mm and CIRF > 4 mm.

Results: The mean stone volume and HU were 553.37±338.10 and 1063.5±378.07 respectively. Complete SFR was 59% and 35.7% with stone volume <500 and 500-1000 mm3 (P<0.05) respectively. Similarly, Complete SFR was 66.67% and 33.34% with HU<500 and >1500 (P<0.05) respectively. We achieved complete stone clearance in 18 patients (42.85%), whereas 16 patients (38.09%) had CIRF < 4mm and 8 patients (19.04%) had CIRF > 4mm.Low dose CT KUB detected stones in 57.25% patients who were considered stone free based on X-ray and USG KUB findings.

Conclusion: SFR in RIRS is high for renal stones with lower stone volume and low HU. Low dose CT KUB allows more accurate detection of residual fragments than X-ray and USG KUB during follow up of patients after RIRS.