Can a cutoff value for cystatin C in the operative setting be determined to predict kidney function after liver transplantation?

Correct assessment and follow-up of kidney function is essential in liver transplant recipients. Glomerular filtration rate (GFR) represents the functional capacity of the kidney. The GFR is generally determined on the basis of creatinine clearance using several methods. It has been suggested that cystatin C be used rather than GFR. Production of cystatin C is not dependent on the same factors as creatinine. It is filtered and completely metabolized in the glomeruli, and is not secreted by the kidney tubules. The objective of this study was to determine a preoperative cutoff value for cystatin C based on kidney function estimated after liver transplantation. At prefixed times before and after orthotopic liver transplantation (OLT), serum cystatin C and creatinine concentrations were measured, and GFR was calculated using the Cockroft-Gault equation. Patients were divided into 2 groups according to GFR on postoperative days 1 to 5. Group 1 (healthy recipients) included patients with post-OLT GFR greater than 70 mL/min; and group 2 (kidney-impaired recipients), post-OLT GFR less than 70 mL/min. Group 2 demonstrated greater risk of postoperative complications, abnormal postoperative creatinine concentrations and GFR values, and worse patient and graft survival. Based on the preoperative cystatin C concentration, postoperative kidney function can be assessed. The cutoff value for preoperative cystatin was determined using receiver operating characteristics analysis. When the preoperative cystatin C concentration exceeded 1.28 mg/L, the postoperative GFR was less than 70 mL/min in the first 5 days after OLT. These findings suggest that if the cystatin C concentration exceeds the cutoff point preoperatively, there will be deterioration of kidney function after OLT. Along with other researchers, we suggest that cystatin C is a sensitive marker of post-OLT kidney function.