Reduced radiation exposure with the use of an air retrograde pyelogram during fluoroscopic access for percutaneous nephrolithotomy

Introduction: Fluoroscopy with retrograde pyelogram is commonly used to obtain access for percutaneous nephrolithotomy (PNL). Our practice uses room air for retrograde identification of calyceal anatomy. Herein we explore whether an air pyelogram was associated with a decrease in radiation exposure compared with standard retrograde pyelogram. Methods: We retrospectively reviewed all PNL procedures performed at our institution over the past 2 years. Of the 260 PNL procedures performed during the study period, 96 had information on radiation dosage required for analysis. The effective dose (ED) was calculated using accepted conversion tables. Multivariable linear regression was used to determine the association between ED and the use of air pyelogram controlling for factors thought to affect radiation exposure. Results: Of the 96 PNL procedures included in the study, 60 (63%) were performed with an air retrograde pyelogram (AP) and 36 (37%) used contrast retrograde pyelogram (CP). Both groups were matched in terms of age, body mass index, stone burden, and number of access tracts. Multivariable linear regression showed significantly lower radiation exposure in the AP group than in the CP group (p = 0.001). There was no difference in fluoroscopy time between the two groups. Using an AP lowered the mean adjusted ED nearly twofold, from 7.67 (CI = 5.99-9.81) to 4.45 (CI = 3.68-5.38) mSv. Conclusions: An air retrograde pyelogram is associated with decreased radiation exposure during PNL when compared with a contrast retrograde pyelogram.