BACKGROUND AND AIM Acute kidney injury (AKI) is a common complication in patients with liver cirrhosis, and its impact on the clinical course is increasingly recognized. Diagnostic classification systems for AKI in cirrhosis have been suggested. The prognostic significance of the respective AKI stages remains to be evaluated in decompensated cirrhosis with ascites. METHODS Data of consecutive patients with cirrhosis and ascites undergoing paracentesis at a tertiary care center were analyzed. AKI was defined as an increase in serum creatinine of ≥ 0.3 mg/dL or by ≥ 50% within 7 days after paracentesis, and classified according to (i) revised Acute Kidney Injury Network (AKIN) criteria and (ii) modified AKI criteria for cirrhosis (C-AKI). In contrast to AKIN, C-AKI stage A discriminates prognosis based on an absolute creatinine cut-off at < 1.5 mg/dL versus C-AKI stage B at ≥ 1.5 mg/dL. RESULTS The final study cohort included 239 patients. Median transplant-free survival was 768 days (95% confidence interval [CI]: 331-1205 days) without AKI, 198 (0-446) in AKI-1, 91 (0-225) in AKI-2, 19 (0-40) and in AKI-3, whereas it was 89 (20-158) days in C-AKI-A, 384 (0-1063) in C-AKI-B, and 22 (7-776) in C-AKI-C. Mild AKI was already associated with significantly increased 30-day mortality (AKI-1:26.4%, C-AKI-A:33.3%) as compared with patients without AKI (14.3%), even when serum creatinine remained within normal range (< 1.2 mg/dL) we observed a significant 30-day mortality. CONCLUSION AKIN criteria-considering small increases in serum creatinine rather than absolute thresholds-seem to be more accurate for estimating prognosis of AKI after paracentesis than C-AKI criteria. Even patients developing AKI-1 with "normal" serum creatinine are at increased risk for mortality.