From body mass index to waist circumference: a paradigm shift in assessing access complexity in percutaneous nephrolithotomy- comparative study.

To compare waist circumference (WC) and body mass index (BMI) on renal access difficulty during percutaneous nephrolithotomy surgery (PCNL) with fluoroscopic guided PCNL (FPCNL) and ultrasonographic guided PCNL (UPCNL) access techniques. 109 patients underwent PCNL, with 63 FGPNL and 46 UPCNL techniques. Patients were categorized as WC ≥ 90 or less cm and BMI ≥ 30 or less. Stone-free rate (SFR) was presented as Grade A (no stone), Grade B (≤ 2 mm), Grade C (A + B + 2.1-4 mm), and > 4 mm, based on a non-contrast computed tomography scan. The difficulty level of access was evaluated by number of accesses attempted (NAA) and access time (AT). SFR was similar between patients with low and high WC and BMI (40% for BMI < 30 vs. 42% for BMI > 30, p = 0.389 and 43.7% for WC < 90 vs. 30.7% for WC > 90, p = 0.779). SFR is also similar between UPCNL (41.3%) and FPCNL (44.4%) techniques, p = 0.733. In the UPCNL technique, increased WC, not BMI, is associated with increased NAA and AT. In the FPCNL technique, however, BMI and WC did not affect access parameters. A linear regression analysis indicated that only WC and hydronephroses levels had reached a prediction power for an AT and NAA (p < 0.05). In patients with central obesity, WC may be a more reliable predictor than BMI for estimating access difficulty in the UPCNL technique. While UPCNL appears to have a safety advantage over FPCNL regarding radiation exposure, FPCNL may be a more suitable option for obese patients.