Association of postoperative new-onset proteinuria with mortality and kidney function decline after major surgery: a retrospective multicenter cohort study

Background: Despite its potential clinical significance, the epidemiology and prognostic implications of postoperative new-onset proteinuria remain poorly characterized in major surgical populations. This national cohort study investigated the association between postoperative new-onset proteinuria and adverse outcomes in Chinese patients undergoing major surgery. Materials and methods: The study included participants aged ≥16 years who underwent major surgery between 2000 and 2022 from the China Renal Data System database. Postoperative dipstick proteinuria (measured within 30 days) was categorized as negative, trace, 1+, or ≥2+. The primary outcome was 30-day mortality. The secondary outcomes included 1-year mortality and a composite kidney outcome assessed via the postoperative estimated glomerular filtration rate. Multivariable Cox regression models were used to analyze the associations between postoperative new-onset proteinuria and outcomes, adjusted for pertinent covariates. Results: Postoperative new-onset proteinuria (dipstick: ≥ trace) was identified in 25.3% (12 829/50 728) of participants. The 30-day mortality rate was significantly higher in participants with postoperative new-onset proteinuria (6.5%, 829/12 829) than in those without (1.7%, 660/37 899). Multivariable-adjusted analyses demonstrated significant associations between postoperative new-onset proteinuria and adverse outcomes, with ≥2+ proteinuria showing the highest risks for 30-day mortality [adjusted hazard ratio (aHR) 2.14, 95% CI 1.56–2.92], 1–year mortality (aHR 1.65, 1.37–1.98), and kidney function decline (aHR 2.21, 1.65–2.94) in fully adjusted models (all P < 0.001). Subgroup analyses revealed that treatment with renin–angiotensin system inhibitors or statins significantly attenuated the proteinuria–mortality associations (both P for interaction < 0.001). Compared with participants without postoperative new-onset proteinuria, those with persistent proteinuria after major surgery exhibited a higher 1-year mortality risk (aHR 1.8, 95% CI 1.35–2.41). Conclusions: In this large national cohort, postoperative new-onset proteinuria affected one-quarter of patients undergoing major surgery and independently predicted higher mortality and a decline in kidney function. These findings underscore the importance of routine postoperative urinary screening among patients undergoing major surgery. Further research is needed to determine whether targeted management of proteinuria could improve patient outcomes.