Factors Affecting Patient Radiation Exposure During

Percutaneous Nephrolithotomy

John G. Mancini, Eliza M. Raymundo, Michael Lipkin, Dorit Zilberman, Daniel Yong,

Lionel L. Bañez, Michael J. Miller, Glenn M. Preminger and Michael N. Ferrandino*

From the Duke University Medical Center, Durham, North Carolina
Purpose:We identified patient and stone characteristics that may contribute to increased radiation exposure during percutaneous nephrolithotomy and offer technique modifications to limit the radiation dose.Material and Methods: We reviewed the records of 96 patients who underwent percutaneous nephrolithotomy in the last 2 years. The effective radiation dosewas calculated using accepted conversion tables. We performed multivariate linear regression to determine the association of the effective radiation dose withspecific patient, stone and procedural characteristics.Results: Mean  SD patient age was 51.5  13.4 years and 62.5% of thepatients were female. Median body mass index was 32.0 9.7 kg/m2 (range16.2 to 59.6) and the median stone burden was 4 cm2. Increased body mass index (p 0.001), higher stone burden (p  0.013), stone nonbranched configuration(p  0.002) and a greater number of percutaneous access tracts(p  0.040) were significantly associated with an increased effective radiationdose. Specifically obese patients with a body mass index of 30 to 39.9 kg/m2had a more than 2-fold increase in the mean adjusted effective radiation dose and morbidly obese patients with a body mass index of 40 kg/m2 had a greater than 3-fold increase vs that in normal weight patients with a body mass index of less than 25 kg/m2 (6.49 and 9.13 mSv, respectively, vs 2.66,p 0.001). Other stone specific parameters, including site and composition,percutaneous access site and estimated blood loss were not associated with theeffective radiation dose.

Conclusions: Patients with higher body mass index, greater stone burden, nonbranched stones and multiple nephrostomy access tracts are at risk for increasedradiation exposure during percutaneous nephrolithotomy. Urologists must see alternative strategies to minimize radiation exposure, such as tighter collimationto the region of interest, judicious use of magnification and the acquisition of as few images as possible during stone removal.