Upper Calyx Approachability through a Lower Calyx Access for Prone Versus Supine Percutaneous Nephrolithotomy

Upper calyx endoscopic approachability through the lower calyx is significantly higher in supine than in prone percutaneous nephrolithotomies, possibly due to a thinner body wall, a thinner muscular layer, a lower muscle-to-fat thickness ratio and a wider angle between the lower and upper calyx axes.