FACTORS AFFECTING PATIENT RADIATION EXPOSURE DURING PRONE AND SUPINE PERCUTANEOUS NEPHROLITHOTOMY.

Purpose Radiation exposure from fluoroscopy poses risks to patients and surgeons. Percutaneous Nephrolithotomy (PCNL) has traditionally required fluoroscopy, however the use of ultrasound (US) has decreased radiation exposure. US-guidance in supine PCNL may further reduce radiation exposure. In this study we investigate patient and operative factors affecting fluoroscopy time (s), total radiation dose (mGy) and effective radiation dose (ERD) (mSv) in patients undergoing US-guided supine or prone PCNL. Methods: We performed a retrospective study of patients undergoing US-guided PCNL in prone position and supine position. Patients with multiple access tracts, pre-existing renal access or fluoroscopic renal access were excluded. Patient demographic, radiologic and operative data were collected, and compared between the two groups. Results: 99 patients were included: 45 prone (P-PCNL) and 54 supine (S-PCNL). There were no significant demographic differences between the two groups. Operative time, access location, tract length and total radiation dose (mGy) also did not differ. S-PCNL was associated with lower ERD (2.92mSv ± 0.32 vs 5.3mSv ± 0.7, p=0.0014) despite increased fluoroscopy time (86.32s ± 7.7 vs. 51.00s ± 5.1, p=0.004), and was more likely a mini-PCNL (35.2‰ vs 15.9‰, p=0.032). In multivariate analysis, supine PCNL remained associated with reduced ERD compared to prone (p=0.002), whereas BMI (p<0.001) and staghorn calculi (p<0.001) were independently associated with increased ERD.