Association between a 24-h increase in blood urea nitrogen and clinical outcomes in acute non-variceal upper gastrointestinal bleeding: a dual-center retrospective cohort study

Abstract

Background and aim: Blood urea nitrogen (BUN) is incorporated into admission-based risk scores for acute non-variceal upper gastrointestinal bleeding (NVUGIB); however, the clinical relevance of early in-hospital BUN kinetics remains unclear. Objectives: To evaluate whether a 24-h increase in BUN is independently associated with adverse clinical outcomes in patients with acute NVUGIB. Design: Dual-center retrospective cohort study. Methods: We conducted a dual-center retrospective cohort study of adult patients with endoscopically confirmed NVUGIB admitted between 2018 and 2023. The exposure was defined as any absolute increase in BUN within 18–30 h after the baseline measurement at presentation. The primary outcome was 30-day all-cause mortality. Secondary outcomes included in-hospital mortality, in-hospital rebleeding, red blood cell transfusion, length of hospital stay, and need for radiologic or surgical intervention. Multivariable regression was performed in a propensity score-matched cohort with confirmatory analyses in the original cohort. Results: Among 611 patients, 218 (35.7%) demonstrated a 24-h increase in BUN. Propensity score matching yielded 400 patients (200 per group). In the matched cohort, a 24-h BUN increase was independently associated with higher 30-day mortality (adjusted odds ratio (aOR) 3.307; 95% confidence interval (CI) 1.604–6.819) and in-hospital mortality (aOR 2.732; 95% CI 1.208–6.178). No independent associations were observed with rebleeding, transfusion requirements, or radiologic/surgical intervention. Conclusion: An increase in BUN within the first 24 h of hospitalization is independently associated with higher short-term mortality in acute NVUGIB. Early BUN kinetics may serve as a complementary risk marker, but prospective validation and formal predictive-performance testing are needed before clinical integration.