New computed tomographic predictors of complicated perioperative course of 17.5F mini-percutaneous nephrolithotomy (mini-PNL).

PURPOSE

Radiological parameters predicting a postoperative stone-free status (SFS) or a complicated perioperative course of mini-PNL, are scarce. Our aim was to identify such factors for prone 17.5F mini-PNL.

METHODS

A monocentric cohort of 103 cases was retrospectively analysed for factors predicting SFS and relevant complications, i.e. Clavien-Dindo (CD) ≥ 2. Parameters measured on preoperative supine CT included maximal stone diameter, skin-to-stone distance (SSD), ideal tract length (ITL), access angle, minimal T12-Lower Kidney Pole distance (T12LP) and minimal Iliac Crest-Lower Kidney Pole distance (ICLP). Infundibulopelvic angle (IPA) was measured on intraoperative pyelography.

RESULTS

The median maximal stone diameter was lower in cases with postoperative SFS [16 mm (Min. 10; Max. 35) vs. 20 mm (Min. 6; Max. 85), p = 0.0052]. CD ≥ 2 was more frequent in cases with a bigger stone burden [19 mm (Min. 13; Max. 85) vs. 16 mm (Min. 6; Max. 49), p = 0.0056] and with the ribs in the access angle [7/23 (30.43%) vs. 8/76 (10.53%); p = 0.0454]. T12LP significantly differed in cases with and without CD ≥ 2 [80.48 mm (± 21.31) vs. 90.43 mm (± 19.42), p = 0.0397]; however, it had no influence on SFS (p > 0.05). SSD, ITL, IPA and ICLP were significant regarding neither SFS nor CD ≥ 2 prevalence (p > 0.05). Using multivariate logistic regression, T12LP was confirmed as an independent predictor on CD ≥ 2 prevalence.

CONCLUSIONS

Preoperative computed tomographic factors indicating elevated kidney position influence perioperative course of mini-PNL. T12LP and the presence of ribs in the access angle are, apart from stone diameter, the most useful indicators for cases at risk of CD ≥ 2.