Metabolic stone workup abnormalities are not as important as stone culture in patients with recurrent stones undergoing percutaneous nephrolithotomy

To investigate the association between metabolic urinary abnormalities and urinary tract infection (UTI) and the stone recurrence status in patients undergoing percutaneous nephrolithotomy (PCNL).

A prospective evaluation was performed for patients who underwent PCNL between November 2019 and November 2021 and met the inclusion criteria.

Patients with previous stone interventions were classified as recurrent stone formers.

Before PCNL, a 24 h metabolic stone workup and midstream urine culture (MSU-C) were done.

Renal pelvis (RP-C) and stones (S-C) cultures were collected during the procedure.

The association between the metabolic workup and UTI results with stone recurrence was evaluated using univariate and multivariate analyses.

The study included 210 patients.

UTI factors that showed significant association with stone recurrence included positive S-C [51 (60.7%) vs 23 (18.2%), p < 0.001], positive MSU-C [37 (44.1%) vs 30 (23.8%), p = 0.002], and positive RP-C [17 (20.2%) vs 12 (9.5%), p = 0.03].

Other factors were mean ± SD GFR (ml/min) (65 ± 13.1 vs 59.5 ± 13.1, p = 0.003), calcium-containing stones [47 (55.9%) vs 48 (38.1%), p = 0.01], median (IQR) urinary citrate levels (mg/day) [333 (123–512.5) vs 221.5 (120.3–412), p = 0.04], and mean ± SD urinary pH (6.1 ± 1 vs 5.6 ± 0.7, p < 0.001).

On multivariate analysis, only positive S-C was the significant predictor of stone recurrence (odds ratio: 9.9, 95% confidence interval [CI] (3.8–28.6), p < 0.001).

Positive S-C, and not metabolic abnormalities, was the only independent factor associated with stone recurrence.

A focus on preventing UTI might prevent further stone recurrence.