BMC Nephrol. 2026 May 25. doi: 10.1186/s12882-026-05072-z. Online ahead of print.
ABSTRACT
BACKGROUND: We evaluated whether immediate postoperative urine dipstick occult blood after on-pump cardiac surgery could serve as an early indicator of high-risk cardiac surgery-associated acute kidney injury (CSA-AKI).
METHODS: This single-center retrospective study included 11,782 adult patients undergoing elective on-pump cardiac surgery (2018-2024), excluding those with preoperative chronic kidney disease (CKD, stage 3-5), positive preoperative urine occult blood, or postoperative microscopic hematuria. The primary outcome was any-stage CSA-AKI within 7 days after surgery. Multivariable logistic regression was used to evaluate the independent association between immediate postoperative urine occult blood and CSA-AKI. The predictive value was assessed by C-index, the net reclassification improvement index, and integrated discrimination improvement. The goodness-of-fit of models was evaluated through Akaike information criterion, Bayesian information criterion and likelihood ratio test.
RESULTS: CSA-AKI occurred in 32.8% of patients, rising progressively across urine occult blood categories from 28.8% (negative group) to 37.9% (3 + group). After multivariable adjustment, 3 + urine occult blood was independently associated with higher odds of any-stage CSA-AKI (adjusted odds ratio [aOR], 1.630; 95% confidence interval [CI], 1.463-1.817; P < 0.001) and early CSA-AKI within 48 h (aOR, 1.692; 95% CI, 1.513-1.889; P < 0.001). Both 2 + and 3 + urine occult blood were independently associated with stage 2-3 CSA-AKI. Integrating urine occult blood into a clinical risk model that included established CSA-AKI predictors yielded a modest improvement in prognostic prediction and model fit.
CONCLUSION: Immediate postoperative urine dipstick occult blood positivity was independently associated with an increased risk of CSA-AKI. As a simple and easily available biomarker, it may serve as an early indicator to identify patients at high risk of CSA-AKI in this selected cohort of adult patients undergoing elective on-pump cardiac surgery. Because direct markers of hemolysis or urinary heme proteins were not measured, the underlying biological mechanisms remain uncertain and require prospective validation.
PMID:42185772 | DOI:10.1186/s12882-026-05072-z