Analysis of the Skin to Calyceal Distance (SCD) to the Upper Pole Calyx Among Filipino Patients: A Guide to Upper Pole Access Percutaneous Nephrolithotomy (PCNL)

Abstract

Objective: Precise entry to the upper posterior calyx is key to a successful and safe upper pole access PCNL. The surgeon's knowledge of the average skin to calyceal distance can serve as a guide to avoid inadvertent injury to both the kidney and collateral organs during the percutaneous puncture.

Methods: The authors analyzed the radiologic images of 84 patients who underwent unenhanced 64- slice helical CT scan (Toshiba®). Skin-to-calyceal distance (SCD) to the upper posterior calyx were measured using the Vitrea® software inherent to the CT scan.

Results: The mean SCDs in non-hydronephrotic kidneys were 54.9 ± 13.7 mm and 61.4 ± 12.5 mm on the right and left, respectively while in hydronephrotic kidneys, the mean SCDs were 60.3 ± 11.8 mm and 58.6 ± 13.1 mm on the right and left, respectively. There was no statistically significant difference between the right and left upper pole SCD in both groups (p = 0.84).

Conclusion: The mean SCD to the upper posterior calyx among Filipino adults is about 6.0 cm. By limiting the depth of the initial puncture to within this distance, the endourologist may avoid overshooting the targeted calyx, thus avoiding undue injury to the kidney or intraabdominal structures.