J-shaped association between blood urea nitrogen-to-creatinine ratio and mortality in critically ill patients with acute pancreatitis: a retrospective cohort study using the MIMIC-IV database

Both blood urea nitrogen (BUN) and creatinine (Cr) are indicators of kidney function, and the BUN/Cr ratio has been identified as an independent prognostic marker for adverse outcomes in critically ill patients with various conditions. However, the relationship between the BUN/Cr ratio and long-term mortality in critically ill patients with acute pancreatitis (AP) remains unclear. Hence, the primary objective of this study was to determine the prognostic value of the BUN/Cr ratio in patients with AP. We conducted a retrospective cohort study using data from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. The primary exposure variable was the BUN/Cr ratio at intensive care unit (ICU) admission, and the primary outcome was 365-day all-cause mortality. Kaplan–Meier analyses and multivariate Cox proportional hazards models were used to assess this relationship, while restricted cubic spline (RCS) was used to explore potential non-linear associations. In addition, subgroup analyses were conducted to assess consistency between groups. A total of 850 critically ill patients with AP were included, with a mean age of 59.61 years, 58.59% male, and an overall 365-day mortality rate of 20.94%. Patients in the highest BUN/Cr quartile had significantly higher mortality rates compared to those in lower quartiles. Multivariate Cox regression analysis demonstrated that, even after adjusting for potential confounders, an elevated BUN/Cr ratio remained an independent predictor of increased 28-day and 365-day mortality. RCS analysis confirmed a J-shaped relationship between the BUN/Cr ratio and 28-day and 365-day mortality, with a sharp increase in the risk of death above the 16.80 threshold. Subgroup analysis indicated that this association was consistent across various patient characteristics. This study identified a non-linear relationship between the BUN/Cr ratio and 365-day mortality in critically ill patients with AP, suggesting that the BUN/Cr ratio may serve as an easily accessible, cost-effective, and accurate prognostic marker for this population.