Why and how to measure renal function in patients with liver disease.

Patients with advanced liver disease frequently have impaired renal function. Both acute kidney injury (AKI) and chronic kidney disease (CKD) are quite common in patients with cirrhosis and both are associated with a worse prognosis in these patients. A careful assessment of renal function is highly important in these patients to help physicians determine their diagnosis, prognosis and therapeutic management and to define transplantation strategies (liver transplantation alone vs simultaneous liver and kidney transplantation). Although they are still widely used in clinical practice, conventional biomarkers of renal function such as serum creatinine have several limitations in these patients. Recent progress has been made in the evaluation of renal function and new diagnostic criteria for AKI have been proposed. However, certain issues such as the noninvasive assessment of the glomerular filtration rate and/or improvement in the differential diagnosis between hepatorenal syndrome and acute tubular necrosis must still be addressed. The purposes of this paper are: (i) to highlight the importance of the evaluation of renal function in patients with cirrhosis; (ii) to review the state of the art in the assessment of renal function in these patients as well as advances that we expect will be made to improve the accuracy of available tools.