Acute pancreatitis: diagnostic value of blood urea nitrogen levels in assessing disease severity within the first 24 hours

Objective. To investigate the relationship between blood urea nitrogen (BUN) levels and the severity of acute pancreatitis (AP), and to assess the stratification potential of this parameter within the first 24 hours of disease onset. Materials and methods. A prospective longitudinal study was conducted from 2020 to 2025, enrolling 57 patients with confirmed AP, stratified according to the Atlanta 2012 classification. Statistical analysis of polychoric association was performed using Pearson’s coefficient of contingency (C) and the phi-squared (ϕ2 ) coefficient. A threshold BUN value of ≥ 25 mg/dL (based on BISAP criteria) was used for analysis. Results and discussion. Our findings indicate that a BUN level exceeding 25 mg/dL did not show a statistically significant correlation with AP severity during the first 24 hours of the disease (C=0.16). Interestingly, over half of the patients with mild AP (15 out of 29) presented with elevated BUN. Among those with moderately severe AP, 43.8% had elevated BUN, while 66.7% of patients with severe AP also showed increased levels. These results contradict some previous studies that suggested BUN’s prognostic value for mortality, but they support the hypothesis that an elevated BUN might be a consequence of later systemic complications of AP rather than an early marker of severity. The considerable variability in optimal BUN cutoff values across different studies (ranging from 7.8 to 37.3 mg/dL) further underscores the lack of consensus regarding its prognostic role in the early stages of the disease. Conclusions. An elevated BUN level (above 25 mg/dL) is not a statistically significant predictor of acute pancreatitis severity within the first 24 hours of onset, making it unsuitable for the early verification of severe AP when assessed in isolation. This highlights the need to re-evaluate its significance in the early diagnosis of AP and excludes its use as a component of a new integrated system for AP severity stratification.