Arising from: Pham P-TT et al. (2007) Renal function outcomes following liver transplantation and combined liver–kidney transplantation. Nat Clin Pract Nephrol 3: 507–514 doi:10.1038/ncpneph0574

Author's response: Pham P-TT et al. (2008) Cystatin C has prognostic value after liver transplantation. Nat Clin Pract Nephrol [doi:10.1038/ncpneph0766]

We read the Review by Phuong-Thu T Pham, Phuong-Chi T Pham and Alan H Wilkinson with interest. The authors discussed the growing problem of renal failure before and after liver transplantation. The decision of whether to perform liver transplantation alone or in combination with kidney transplantation can be crucial. No currently used parameter can predict progression of chronic renal failure, and it is known that early liver transplantation has a positive effect on renal function in patients whose kidneys are impaired before the procedure. Early detection of renal dysfunction and identification of risk factors for this dysfunction could, therefore, help to lower the incidence and ameliorate progression of chronic renal failure.

The value of serum creatinine as a prognostic indicator of glomerular filtration rate (GFR) is limited by several factors, mainly the nonlinear relationship between creatinine concentration and GFR.1 A laboratory test that has high sensitivity for the detection of renal dysfunction is, therefore, needed for patients undergoing liver transplantation. Cystatin C is produced by nucleated cells2 and excreted only by the kidney; its concentration is independent of muscle catabolism.3,4 The diagnostic value of cystatin C, relative to that of creatinine, has been described elsewhere;5 it has a sensitivity of 96% for detection of moderately decreased GFR.6

Since November 2003, we have collected data from 90 patients undergoing liver transplantation. Cystatin C levels were monitored in order to test the sensitivity of this parameter for detection of early kidney failure, in comparison to that of serum creatinine level and creatinine clearance. Risk profiles for renal dysfunction before and after surgery were documented as usual.

When creatinine level, creatinine clearance and cystatin C concentration were analyzed and compared with respect to sensitivity and specificity, cystatin C had clear prognostic significance (P < 0.05 at any timepoint). By contrast, neither creatinine level or creatinine clearance had significant prognostic value (Supplementary Table 1). The renal function of all patients with physiological cystatin C levels prior to liver transplantation remained stable, whereas all patients with pathological cystatin C concentrations prior to liver transplantation developed kidney dysfunction after the procedure.

Our data support the hypothesis that careful individual screening of patients before liver transplantation is important for guiding the surgical aspects of the procedure, and can extensively influence long-term patient outcome. In this context, the importance of laboratory monitoring of patients undergoing transplantation is unquestionable. In our experience, cystatin C has high prognostic value for detection of early stage kidney dysfunction after liver transplantation. We, therefore, suggest that cystatin C could be another helpful marker for the screening and monitoring of patients before and after liver transplantation. Further studies in this field are warranted.