Relevance of New Definitions to Incidence and Prognosis of Acute Kidney Injury in Hospitalized Patients with Cirrhosis: A Retrospective Population-Based Cohort Study

Abstract

Background: The implementation of new serum creatinine (SCr)-based criteria for acute kidney injury (AKI) has brought to light several areas of uncertainty in patients with cirrhosis.

Study design: Population-based cohort study.

Setting & participants: Adults with cirrhosis hospitalized between 2002-2012.

Predictor: We aimed to address the prognostic implications of the new AKI criteria in cirrhosis.

Outcomes: Baseline kidney function was defined from all outpatient SCr within 3 months before hospitalization. Cox proportional hazards models were fit to examine associations between AKI, renal recovery and all-cause mortality.

Results: 4,733 patients were studied. The 30-day mortality was higher for participants with AKI (43.9% vs 8.5%; p-value<0.001), and increased with AKI severity. The highest incidence of AKI occurred when the lowest SCr within the three months prior to admission was used to define baseline. The hazard ratio for mortality using the lowest SCr within 3 months and the closest pre-admission SCr (definition suggested by the recent consensus guideline) were similar, validating the use of the latter measure. As compared to patients without AKI, stage 1 AKI with maximum SCr ≤132 mmol/L remained associated with a 3.5-fold increased hazard of death at 30 days (95% CI 2.6 to 4.7).

Limitations: As an observational study, the results were vulnerable to residual confounding and ascertainment bias in the use of laboratory data to identify AKI. We did not have access to liver function or disease etiology variables and were unable to adjust for these in our analyses.

Conclusions: These results confirm the graded relationship between AKI severity, renal recovery, and mortality and further clarify previously discordant reports about the prognostic relevance of new AKI criteria in patients with cirrhosis.

Fig 1. Timeline of exposure status updated by AKI episodes and renal recovery.

Time of an AKI episode is the time of peak in-hospital SCr met AKI criteria during hospitalization. Time of SCr for AKI recovery is the time of closet SCr to 30 days post an AKI episode.

Fig 2. Study flow chart.

SCr, serum creatinine; ESRD, end-stage renal disease; AKI, acute kidney injury.

Fig 3. 30-day mortality according to AKI stages.

The 30-day mortality increased with increasing AKI severity. The numbers at the bottom of the survival curves represent the number of patients at risk at various time points.

Fig 4. 6-month mortality according to AKI recovery (as a time-varying covariate with follow-up from hospital admission for all subjects).

Mortality was lowest in those patients without AKI, higher in who recovered renal function and highest in those patients without renal recovery. The numbers at the bottom of the survival curves represent the number of patients at risk in each AKI recovery group at various time points.

Fig 5. 30-day mortality according to AKI with or without Scr >132.6 mmol/l.

The numbers at the bottom of the survival curves represent the number of patients at risk in each AKI and renal recovery group at various time points. (AKI stage 1a: AKI stage 1 with max SCr< = 132.6 μmol/L; AKI stage 1b: AKI stage 1 with max SCr>132.6 μmol/L)