Incidence of posterolateral and retrorenal colon in supine and prone position in percutaneous nephrolithotomy

Colon injury is a distressing complication during percutaneous nephrolithotomy (PCNL). Posterolateral colon (PLC) and retrorenal colon (RRC) are known to be the risk factors of colonic injury during PCNL. We evaluated the incidence of PLC and RRC in both supine and prone position of patients who underwent PCNL in our institution, and determined the risk factors of PLC and RRC through a review of computed tomography (CT) scan. To define PLC and RRC, we divided kidney into anterior, anterolateral, posterolateral and retrorenal zone by drawing three parallel lines in the CT scan. Among a total of 102 patients, PLC and RRC were identified in 16 (15.7%) cases in supine, and 25 (24.5%) cases in the prone position. PLC and RRC were most frequently present in the upper and lower pole of the left kidney in prone position compared to supine (p value less than 0.001). Risk factors of PLC and RRC in the prone position were old age (over 68), lower body mass index (BMI), and thinner perirenal fat layer. Therefore, an initial percutaneous puncture in PCNL needs to be carefully accessed to those patients with such high risks of colon injury.