Radiation Exposure during Ureterorenoscopy and Laser Lithotripsy: An Analysis of Stone Characteristics

Stone formers often have a chronic exposure to significant quantities of ionising radiation from radiological investigations and interventions. Predicting radiation exposure would allow the clinician to quantify expected cumulative radiation and find strategies to minimise exposure. We evaluated radiation exposure during ureteroscopy and laser lithotripsy (URS + LL) for a single stone episode and correlated the results to stone characteristics.

Data was collected retrospectively for all patients undergoing URS + LL in our institution over a 1 year period. Patients with multiple stones, staghorn stones or incomplete stone clearance were excluded to simplify the analysis. Patient characteristics, fluoroscopy data and stone characteristics were recorded.

We included 302 consecutive patients in the study. The majority of stones were located in the renal calyces/pelvis (54%) with the rest located in the upper (18%), middle (13%) and lower ureter (15%). Mean stone diameter was 9.9 mm (range 4-30 mm). Mean radiation exposure time during URS + LL was 44 s (range 12-119 s) with a mean total radiation exposure of 7.5 milligray (mGy; range 1.2-29.7 mGy). Renal stones were associated with 27% higher radiation exposure compared to ureteral stones (8.3 vs. 6.7 mGy; p = 0.02). There was a positive correlation between stone diameter and radiation exposure (Spearman's correlation coefficient ρ = 0.28; p < 0.001). Stones with diameter greater than 10 mm were associated with 37% higher radiation exposure compared to smaller stones (9.1 vs. 6.6 mGy; p < 0.001).

There is a direct correlation between stone burden, as well as location, and radiation exposure during URS + LL. Clinicians should consider strategies to reduce total radiation exposure in recurrent stone formers at risk of high radiation exposure by limiting screening time, using pulsed rather than continuous fluoroscopy, management with primary URS + LL, or using ultrasound guidance.