Upper Calyx Approachability through a Lower Calyx Access: Comparison between Prone and Supine PCNL and Assessment of Anatomical Factors That May Influence It Using Three-dimensional CT Reconstructions

PURPOSE - To assess the approachability of the upper calyx through a lower calyx access in prone and supine percutaneous nephrolithotomies (PCNLs), and to employ computerized tomography (CT) to analyze anatomical factors that may influence it.

MATERIALS AND METHODS - A prospective series of 45 patients treated by PCNL were operated in prone (n=20) and supine (n=25) positions. CT-simulated access to the lower calyx and upper calyx longitudinal axes were used for measuring skin to lower calyx distance, body wall, muscular and fat thicknesses, muscle:fat thickness ratio, and the angle between the lower calyx tract and the upper calyx axis. The intraoperative approachability to the upper calyx was also evaluated.

RESULTS - The upper calyx was successfully approached in 20% of prone and 80% of supine PCNLs (p < 0.0001). The skin-lower calyx distance was 98.4 mm (65.3-128.6) in prone and 98.7 mm (60.8-150) in supine positions (p=0.99). The body wall and muscular thicknesses and the muscle:fat thickness ratio were significantly lower in the supine PCNLs compared to the prone PCNLs (p < 0.001, < 0.0005, and <0.05, respectively). The average angle between the lower and upper calyces axes was wide in the supine position [141° (90-170°)] and acute in the prone position [84° (65-110°)] (p < 0.05(E-10)).

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

J Urol. 2015 Aug 5. pii: S0022-5347(15)04510-3. doi: 10.1016/j.juro.2015.07.101. [Epub ahead of print]

Sofer M1, Giusti G2, Proietti S2, Mintz I3, Kabha M3, Matzkin H3, Aviram G4.

1 Endourology Unit.
2 Stone Center at the Department of Urology, Humanitas Clinical and Research Center, Rozzano (MI), Italy.
3 Department of Urology, Tel-Aviv University, Tel-Aviv, Israel.
4 Department of Radiology, Tel-Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv, Israel.