Desoky EAE, et al. - Experts aimed to draw a comparison between the colon and the trajectory of percutaneous nephrolithotomy (PCNL) access both in prone and flank free modified supine (FFMS) positions as measured on CT. They also studied the impact of age, gender, BMI, side and previous renal surgery as influencing factors. They noted that mainly patient position influenced the distance between the colon and assumed PCNL trajectory at a puncture on the posterior axillary line. The colon appeared to be farther in FFMS position than in prone position. BMI and age significantly impacted this distance to a lesser extent.