Ultrasound Guidance to Assist Percutaneous Nephrolithotomy Reduces Radiation Exposure in Obese Patients.
OBJECTIVE
To evaluate the impact of body mass index (BMI) on perioperative outcomes and radiation exposure for ultrasound (US)-guided percutaneous nephrolithotomy (PCNL).


METHODS
Data were prospectively collected for consecutive patients who underwent PCNL at the University of California, San Francisco, from July 2013 to November 2015. Patients were divided into 3 groups according to their BMI: <25 (normal weight), 25-29.9 (overweight), and >30 (obese) kg/m2. Perioperative outcomes were compared between patients who underwent US-guided vs fluoroscopy-guided PCNL.


RESULTS
One hundred thirty-five patients were enrolled; 93 cases were performed under US and 42 under fluoroscopic guidance. US successfully guided renal access in 76.9% of normal weight, 79.0% of overweight, and 45.7% of obese patients (P < .05). Mean fluoroscopic screening time and radiation exposure dose were reduced for US compared to fluoroscopy cases across all BMI categories (P < .05). As BMI increased, radiation exposure dose rose disproportionately faster compared to screening time (P < .001). No significant differences among the BMI groups were found with regard to complication rate, hospital stay, and stone-free status.


CONCLUSIONS
US-guided PCNL may be more difficult in obese patients, but with its use, the overweight and obese experience the largest absolute reduction in radiation exposure. Because these patients are inherently at greater risk for radiation exposure compared to normal weight patients, they may benefit the most from adoption of US for PCNL.
Department of Urology, University of California, San Francisco, San Francisco, CA; Division of Urology, Faculty of Medicine, King Chulalongkorn Memorial Hospital, Chulalongkorn University, The Thai Red Cross Society, Bangkok, Thailand.
Manint
M
Usawachintachit
Department of Urology, University of California, San Francisco, San Francisco, CA.
Selma
S
Masic
Department of Urology, University of California, San Francisco, San Francisco, CA.
Helena C
HC
Chang
Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA.
Isabel E
IE
Allen
Department of Urology, University of California, San Francisco, San Francisco, CA. Electronic address: Tom.Chi@ucsf.edu.
Thomas
T
Chi
D015992:Body Mass Index; D005260:Female; D005471:Fluoroscopy / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D007669:Kidney Calculi / Q000150:complications / Q000175:diagnosis / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D000074642:Nephrolithotomy, Percutaneous / Q000379:methods*; D009765:Obesity / Q000150:complications*; D011446:Prospective Studies; D000069079:Radiation Exposure; D011832:Radiation Injuries / Q000517:prevention & control*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D016896:Treatment Outcome; D014463:Ultrasonography / Q000379:methods*