Introduction:
The blood urea nitrogen to serum albumin ratio (BAR) may serve as a prognostic marker. This study evaluated its association with clinical outcomes in patients with acute pancreatitis (AP).

Material and methods:
We performed a retrospective cohort analysis using data from the MIMIC-IV 2.2 database, including 650 patients diagnosed with AP. The primary outcomes were 90-day and 365-day mortality.Cox proportional hazards models assessed the relationship between BAR and mortality.Restricted cubic spline (RCS) analysis examined the non-linear relationship. Receiver operating characteristic (ROC) curves were generated to evaluate the predictive performance of BAR for mortality. Kaplan-Meier(KM) survival curves were generated to compare outcomes across the BAR groups.

Results:
Among the 650 patients, the mortality rates at 90 days and 365 days were 21.2% and 26.2%, respectively. Higher BAR levels correlated with increased 90-day and 365-day mortality (P < 0.001). BAR had hazard ratios of (HR 1.04, 95% CI 1.02–1.06) for 90-day and (HR 1.04, 95% CI 1.02–1.05) for 365-day mortality. ROC analysis revealed BAR’s AUC was 0.738 for 90-day and 0.714 for 365-day mortality. Subgroup and sensitivity analyses indicated stable results across various conditions.

Conclusions:
Elevated BAR is significantly associated with increased mortality in AP patients, indicating its potential as a valuable prognostic marker in critical care settings.