Background <p>Percutaneous nephrolithotomy (PCNL) is frequently complicated by infectious events, some of which progress to sepsis. Conventional pressure metrics are usually based on instantaneous values, such as peak or mean pressure, and therefore fail to capture the temporal dimension of pressure exposure. This study proposes “time at low pressure” as a novel exposure metric to evaluate its association with infectious complications after PCNL.</p> Methods <p>We conducted a single-centre retrospective cohort study including adult patients who underwent PCNL with continuous intraoperative renal pelvic pressure (RPP) monitoring. The core exposure variable was the proportion of operative time with renal pelvic pressure ≤ 30 mmHg (RPP Time ≤ 30 mmHg, %). The primary outcome was postoperative infectious complications. Multivariable logistic regression, quartile-based trend analysis, restricted cubic spline modelling, and receiver operating characteristic (ROC) analysis were used to examine the relationship between RPP Time and infectious outcomes and to identify an optimal cut-off value.</p> Results <p>Compared with patients without infectious complications, those who developed infection had a significantly lower RPP Time ≤ 30 mmHg (%). After full adjustment for demographic, preoperative, and intraoperative confounders, standardized RPP Time ≤ 30 mmHg (%) was independently and inversely associated with postoperative infection (fully adjusted odds ratio ≈ 0.29 per 1-SD increase; <i>P</i> &lt; 0.001). The incidence and odds of postoperative infectious complications decreased progressively across increasing quartiles of RPP Time ≤ 30 mmHg (%), with a significant linear trend. ROC analysis showed moderate discriminative performance for predicting infectious complications (area under the curve 0.777), and the optimal cut-off was 75.95%. Restricted cubic spline analysis demonstrated a largely linear inverse dose–response relationship between RPP Time ≤ 30 mmHg (%) and infection risk, and subgroup analyses revealed consistent associations across clinically relevant strata without significant interactions.</p> Conclusions <p>A higher proportion of operative time with renal pelvic pressure at or below 30 mmHg was associated with a lower risk of postoperative infectious complications after PCNL. Compared with traditional instantaneous pressure metrics, the “time at low pressure” concept better reflects the pathophysiological continuum from pressure elevation to reflux and infection, and may represent a promising intraoperative indicator for pressure management.</p>