Even mild cases of acute kidney injury after liver transplantation are associated with lower survival for both the patient and the graft. With more severe injury, outcomes are even worse. These findings are in the May issue of Liver Transplantation, a journal published by John Wiley & Sons. The article is also available online at Wiley Interscience (www.interscience.wiley.com).
Acute kidney injury often occurs after liver transplantation because of blood loss or surgery-related events. Previous studies have estimated the incidence rate at 17 to 95 percent—a wide range that reveals the lack of clear diagnostic criteria. To address this problem, researchers led by Yousri Barri of Baylor University Medical Center in Texas sought to find the optimal definition for acute kidney injury after liver transplantation, and determine its impact on patients' long-term outcomes.
They retrospectively studied patients who underwent liver transplantation at Baylor between 1997 and 2005 and applied three commonly used definitions of acute kidney injury, each based on change in serum creatinine from baseline. These were: a rise in serum creatinine of more than .5 mg/dL; a rise of more than 1.0 mg/dL; and a rise of more than 50 percent to above 2 mg/dL. The outcomes for each group of patients were compared to those from a control group that did not have kidney injury.
The majority of liver transplant recipients experienced some degree of acute kidney injury. About 78 percent of the transplant recipients had a rise in creatinine or more than 0.5 mg/dL from baseline, considered mild in severity. About 46 percent had a moderate creatinine increase of 1.0 mg/dL or more, while 14 percent had a marked creatinine increase of 50 percent or more to above 2.0 mg/dL.
"Even mild acute kidney injury defined as rise in serum creatinine of >0.5 mg/dL was associated with reduced patient and graft survival," the authors report. They suggest that this sensitive definition, which captures a large majority of liver transplant recipients, deserves attention and strategies for prevention.
However, the strictest definition of acute kidney injury was associated with the worst outcomes, including higher incidence of cardiovascular events and end-stage renal disease.
"This study shows that acute kidney injury, appropriately defined, has an important impact on long-term renal function and patient and graft survival post-liver transplantation," the authors conclude. "Whether acute kidney injury is the direct cause or simply associated with poor outcome will need further study."
An accompanying editorial by Connie Davis of the University of Washington Medical Center applauds the focus on "a very simple easily available measure, the degree of change in serum creatinine." Barri and colleagues revealed a clear association between this measure and worse outcomes within a few years of the transplant.
"It is time to give kidney dysfunction a clear identity and treatment strategy in the setting of liver transplantation," she concludes.