Acute Kidney Injury (AKI), BUN to Creatinine Ratio, and Local Complications of Acute Pancreatitis (AP)

Purpose: Serum creatinine levels higher than 1.8-2 mg/dl are associated with necrosis in AP. However, during early stage of AKI secondary to hypovolemia, even a large reduction in renal function may only result in a slight increase in creatinine to a value less than 1.8 and a disproportionate rise in BUN. Instead of cutoff, we adopted the widely accepted criteria of AKI proposed by Acute Kidney Injury Network and sought to determine whether AKI and elevated BUN to creatinine ratio (BUN:Cr) on admission predicts local complications in AP. Methods: This retrospective study included consecutive patients admitted with AP to a single tertiary referral center between 03/2007 and 01/2012. Demographic, clinical, radiographic and laboratory data were manually collected. Local complications were defined as acute fluid collection, necrosis, or both on contrast-enhanced CT scan. AKI was defined as an admission serum creatinine greater or equal to 1.5 times the baseline value. Multivariable logistic regression was performed to determine the association of AKI and increased BUN:Cr with the risk of local complications. Since general health and comorbidities may confound this relationship, the analyses were adjusted based on the Charleson Comorbidity Index (CCI). Results: Three hundred twenty-two patients were identified with AP. Of these, 34 patients had AKI on admission. Patients with AKI on admission were at a greater risk of developing local complications (odds ratio 3.2, 95% CI 1.5-7.0). Regarding the BUN:Cr ratio, an ‘effect modification' was found, i.e., the association of BUN:Cr depended on the presence of AKI. Among patients with AKI, the adjusted odds ratio was 1.2 (CI 1.04, 1.4), i.e. for every 1 unit increase in BUN:Cr, the odds of having fluid collection or necrosis increased by 20%. This relationship was not observed among those without AKI. Conclusion: Patients are more likely to develop local AP complications if they have AKI on admission. Among those with AKI, an elevated BUN:Cr ratio further increases this risk by roughly 20% for every unit rise in BUN:Cr. Clinical implication: The presence of acute kidney injury (>50% rise in creatinine from baseline) should prompt aggressive fluid therapy. Prospective studies are warranted to clarify if an intervention is beneficial.Figure: BUN/Creat ratio and fluid collection among patients with AKI (The difference reached statistical significance after adjusting for CCI).