Objective Serum creatinine is a byproduct of muscle metabolism, and low creatinine is postulated to be associated with diminished muscle mass. This study examined the association between low pre-operative serum creatinine and post-operative outcomes.

Methods This retrospective cohort study utilized the 2014–2021 National Surgical Quality Improvement Program to identify patients undergoing surgery with gynecologic oncologists. Patients with missing pre-operative creatinine, end-stage renal disease, sepsis, septic shock, dialysis, or pregnancy were excluded. Pre-operative creatinine was categorized into markedly low (≤0.44 mg/dL), mildly low (0.45–0.64 mg/dL), normal (0.65–0.84 mg/dL), and four categories of elevated levels (0.85–1.04, 1.05–1.24, 1.25–1.44, and ≥1.45 mg/dL). Outcomes included major (≥Grade 3) 30-day complications, categorized into any complications, wound, cardiovascular and pulmonary, renal, infectious, and thromboembolic complications. Also examined were 30-day readmissions, reoperations, and mortality. Logistic regressions assessed the association between creatinine and complications, with stratification by albumin and sensitivity analysis with propensity score matching.

Results Among 84 786 patients, 0.8% had markedly low, 19.6% mildly low, and 50.2% normal creatinine; the remainder had elevated creatinine. As creatinine decreased, the risks of major complications increased in a dose-dependent manner on univariable and multivariable analyses. A total of 9.6% (n=63) markedly low patients experienced major complications, second to creatinine ≥1.45 mg/dL (9.9%, n=141). On multivariable models, both markedly and mildly low creatinine were associated with higher odds of major complications (OR 1.715, 95% CI 1.299 to 2.264 and OR 1.093, 95% CI 1.001 to 1.193) and infections (OR 1.575, 95% CI 1.118 to 2.218 and OR 1.165, 95% CI 1.048 to 1.296) versus normal. Markedly low creatinine had similar ORs to creatinine ≥1.45 mg/dL and was further associated with higher odds of cardiovascular and pulmonary complications (OR 2.301, 95% CI 1.300 to 4.071), readmissions (OR 1.403, 95% CI 1.045 to 1.884), and mortality (OR 2.718, 95% CI 1.050 to 7.031). After albumin stratification, associations persisted for markedly low creatinine. Propensity-weighted analyses demonstrated congruent findings.

Conclusions Low creatinine levels are associated with major post-operative complications in gynecologic oncology in a dose-dependent manner. Low creatinine can offer useful information for pre-operative risk stratification, surgical counseling, and peri-operative management.