Patient Radiation Exposure: Comparison between Supine and Prone Techniques for Percutaneous Nephrolithotomy. Introduction Recent advancements in PCNL for large renal calculi have included supine positioning. Metanalyses have reported decreased operating times and comparable stone-free and complication rates. 1 However, these metanalyses did not comment on the comparison between patient radiation exposure between these two techniques. There is no safe dose of radiation. An effective radiation dose as little as 10mSv may result in the development of a malignancy in 1 in 1000 individuals exposed (NRCNA, 2006). An often overlooked source of significant radiation exposure is fluoroscopy. Urological surgeons should be aware of the cumulative amount of ionizing radiation received by their patients during fluoroscopic procedures. Conclusions Despite a significant decrease in operating duration in the supine PCNL group compared to the prone group; this did not equate to decreased patient radiation exposure. In fact, it was significantly higher in the supine group. This may be partially attributable to increased stone size and BMI in this group. Radiation exposure did correlate with higher body mass index (BMI). This is replicated in studies involving prone PCNL. Other studies have shown higher BMI, greater stone burden, non-branched stones and multiple access tracts in prone PCNL result in higher effective dose rates 2. In our series, radiation exposure did not correlate with stone complexity or learning curve. Further studies are required to investigate the effective radiation dose exposed to patients in supine PCNL. Urologists must be aware of the radiation exposed to our stone patient population so that they can be fully counseled concerning risks and strategies made to minimize exposure. Results Methods 41 consecutive PCNLs (36 patients with 5 patients having a second procedure) between April 2011 to March 2012 with large renal or proximal ureteric calculi were positioned in the modified supine position. A single Consultant was involved, however there were 7 trainees performing punctures (3 Registrars, 4 Fellows) Stones were fragmented using either a lithoclast or ultrasonic lithotripter. For complex staghorn calculi, a second surgeon performed simultaneous renoureteroscopy using the Holmium:YAG laser for fragmentation. The patient demographics, stone size, operating time, cumulative radiation dose (mGy), fluoroscopy time (minutes) and clearance rates were collected prospectively. Radiation dosage was recorded in a dose report from the intraoperative C-arm. The radiation dose measured included all radiation exposure throughout the entire procedure including urethral catheter placement, percutaneous access, tract dilation, stone removal and any ureteroscopic stone treatment. These were compared to the immediate previous 41 prone cases (this group also included 36 patients with 5 patients having a second procedure) and analyzed statistically. Statistics were analyzed using Pearsons correlation test. Aim The purpose of this study is to determine whether there is decreased patient radiation exposure with the supine PCNL compared to the prone PCNL, as would be expected with shorter operating times. References 1 Wu P, Wang L, Wang K. Supine versus prone position in Percutaneous Nephrolithotomy for kidney calculi: a meta-analysis. Int Urol Nephrol. 2011; 43: Mancini J, Raymundo E, Lipkin M, et al. Factors Affecting Pateint Radiation Exposure During Percutaneous Nephrolithotomy. J Urol. 2010; 184: K. Rzetelski-West, Y. Tay, J. Gleeson, P.McCahy Department of Urology, Casey Hospital, Berwick, Victoria. Poster presentation sponsor No. 111 SupineProneP value Age (yrs) p=0.954 Operating time (mins) p=0.003* BMI Median: Range: p=0.067 Stone Size (mm) p=0.040* Length of Stay (days)2.5 p=0.914 Median cumulative radiation dosage (mGy) p=0.009* Median fluoroscopy time (minutes) Median: Range: – 23.7 p=0.984 Pearsons correlation BMI vs Radiation Exposurer=0.66p<0.0001* Complexity vs Radiation dosager=0.21p= Operation no vs Radiation timer=-0.36p= Stone size vs Radiation dosager=0.09p=0.606