Evaluation of renal tubular damage in liver cirrhosis by urinary enzymes and beta-2-microglobulin excretions

Discovery and Validation of a Biomarker Model (PRESERVE) Predictive of Renal Outcomes After Liver Transplantation

BACKGROUND AND AIMS

A high proportion of patients develop chronic kidney disease (CKD) after liver transplantation (LT). We aimed to develop clinical/protein models to predict future glomerular filtration rate (GFR) deterioration in this population.

APPROACH AND RESULTS

In independent multicenter discovery (CTOT14) and single-center validation (BUMC) cohorts, we analyzed kidney injury proteins in serum/plasma samples at month 3 after LT in recipients with preserved GFR who demonstrated subsequent GFR deterioration versus preservation by year 1 and year 5 in the BUMC cohort. In CTOT14, we also examined correlations between serial protein levels and GFR over the first year. A month 3 predictive model was constructed from clinical and protein level variables using the CTOT14 cohort (n = 60). Levels of β-2 microglobulin and CD40 antigen and presence of hepatitis C virus (HCV) infection predicted early (year 1) GFR deterioration (area under the curve [AUC], 0.814). We observed excellent validation of this model (AUC, 0.801) in the BUMC cohort (n = 50) who had both early and late (year 5) GFR deterioration. At an optimal threshold, the model had the following performance characteristics in CTOT14 and BUMC, respectively: accuracy (0.75, 0.8), sensitivity (0.71, 0.67), specificity (0.78, 0.88), positive predictive value (0.74, 0.75), and negative predictive value (0.76, 0.82). In the serial CTOT14 analysis, several proteins, including β-2 microglobulin and CD40, correlated with GFR changes over the first year.

CONCLUSIONS

We have validated a clinical/protein model (PRESERVE) that early after LT can predict future renal deterioration versus preservation with high accuracy. This model may help select recipients at higher risk for subsequent CKD for early, proactive renal sparing strategies.

Protecting the Kidney in Liver Transplant Candidates: Practice-Based Recommendations From the American Society of Transplantation Liver and Intestine Community of Practice

Acute kidney injury (AKI) and chronic kidney disease (CKD) are common in patients awaiting liver transplantation, and both have a marked impact on the perioperative and long-term morbidity and mortality of liver transplant recipients. Consequently, we reviewed the epidemiology of AKI and CKD in patients with end-stage liver disease, highlighted strategies to prevent and manage AKI, evaluated the changing liver transplant waiting list's impact on kidney function, delineated important considerations in simultaneous liver-kidney transplant selection, and projected possible future transplant policy changes and outcomes. This review was assembled by experts in the field and endorsed by the American Society of Transplantation Liver and Intestinal Community of Practice and Board of Directors and provides practice-based recommendations for preservation of kidney function in patients with end-stage liver disease.

Novel serum biomarker candidates for liver fibrosis in hepatitis C patients

BACKGROUND

Liver biopsy is currently the gold standard for assessing liver fibrosis, and no reliable noninvasive diagnostic approach is available. Therefore a suitable serologic biomarker of liver fibrosis is urgently needed.

METHODS

We used a proteomics method based on 2-dimensional gel electrophoresis to identify potential fibrosis biomarkers. Serum samples from patients with varying degrees of hepatic scarring induced by infection with the hepatitis C virus (HCV) were analyzed and compared with serum from healthy controls.

RESULTS

We observed the most prominent differences when we compared serum samples from cirrhotic patients with healthy control serum. Inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4) fragments, alpha1 antichymotrypsin, apolipoprotein L1 (Apo L1), prealbumin, albumin, paraoxonase/arylesterase 1, and zinc-alpha2-glycoprotein were decreased in cirrhotic serum, whereas CD5 antigen-like protein (CD5L) and beta2 glycoprotein I (beta2GPI) were increased. In general, alpha2 macroglobulin (a2M) and immunoglobulin components increased with hepatic fibrosis, whereas haptoglobin and complement components (C3, C4, and factor H-related protein 1) decreased. Novel proteins associated with HCV-induced fibrosis included ITIH4 fragments, complement factor H-related protein 1, CD5L, Apo L1, beta2GPI, and thioester-cleaved products of a2M.

CONCLUSIONS

Assessment of hepatic scarring may be performed with a combination of these novel fibrosis biomarkers, thus eliminating the need for liver biopsy. Further evaluation of these candidate markers needs to be performed in larger patient populations. Diagnosis of fibrosis during early stages will allow early treatment, thereby preventing fibrosis progression.

Renal resistive indexes and some renal functions in liver cirrhotic children

BACKGROUND

The aim of the present study was to investigate renal vascular resistive changes in children with different stages of liver cirrhosis without obvious renal failure.

METHODS

Twenty-nine children (14 girls, 15 boys, mean age 11.6 years) with cirrhosis and 20 healthy children (mean age 10.3 years) were investigated for renal vascular resistance with Doppler ultrasonography, urinary sodium, N-acetyl-beta-D glucosaminidase (NAG) and microalbuminuria excretion.

RESULTS

The measurements of renal resistive indexes (RRI) were significantly higher in cirrhotic patients than the control group (0.69 +/- 0.07 vs 0.62 +/- 0.02, P < 0.0001). RRI measurement was found to be increased in decompensated cirrhotic patients than in compensated cirrhotic patients (0.73 +/- 0.05 vs 0.67 +/- 0.08, P < 0.0001). A significant positive relationship was observed between RRI and child score (r = 0.53). Urine NAG/Cr ratio was significantly higher in cirrhotic patients than in the control subjects (P < 0.001). Microalbumin concentrations were increased in the patients with decompensated cirrhosis than in the controls (P = 0.02). Patients with ascites and portal hypertension showed increased RRI values.

CONCLUSIONS

We conclude that patients with cirrhosis are at risk of renal deterioration, which can not be detected by serum urea, creatinine, and glomerular filtration rate. The increase of RRI is associated with the progress of hepatocellular disease, and also the development of ascites and portal hypertension. Elevated urinary sodium excretion, elevated urinary NAG/Cr ratio and microalbuminuria might have a prognostic value especially in patients with Child scores> 6. Hence, monitoring RRI is a non-invasive means of studying early renal hemodynamic alteration in childhood cirrhosis.

Hypophosphatemia and renal tubular dysfunction in alcoholics. Are they related to liver function impairment?

The study was designed to evaluate (a) the role of reduced renal phosphate reabsorptive capacity assessed as the ratio of maximum capacity for renal phosphate reabsorption (TmPO4) to glomerular filtration rate (GFR) in the pathogenesis of hypophosphatemia in alcoholics, (b) possible mechanisms leading to reduced TmPO4/GFR, and (c) the effect of liver function impairment on TmPO4/GFR. The TmPO4/GFR, its major extrarenal determinants, ratios of urinary excretion gamma-glutamyl transpeptidase and of alpha-glucosidase to GFR (uGGT/GFR and uAGL/GFR), indices of structural damage of renal tubular cells, and fractional clearance of lysozyme, an index of proximal renal function, were evaluated in 31 alcoholics with alcohol-related liver disease, 24 alcoholics without alcohol-related liver disease, 14 patients with non-alcohol-related liver disease, and 25 control subjects. Hypophosphatemia was found in 35% of alcoholics with alcohol-related liver disease, 29% of alcoholics without alcohol-related liver disease, and no patients with non-alcohol-related liver disease. A reduced TmPO4/GFR was the major determinant of hypophosphatemia in both groups of alcoholics. No difference in extrarenal determinants of TmPO4/GFR was found between alcoholics with and without hypophosphatemia. Alcoholics with and without alcohol-related liver disease had increased uGGT/GFR and normal uAGL/GFR regardless of serum phosphate level. Fractional clearance of lysozyme, instead, was increased only in hypophosphatemic alcoholics with and without alcohol-related liver disease. The TmPO4/GFR correlated inversely with the fractional clearance of lysozyme in both groups of alcoholics (P less than 0.01). The TmPO4/GFR and urinary enzymes were normal in patients with non-alcohol-related liver disease. It was concluded that a reduced TmPO4/GFR is involved in the pathogenesis of hypophosphatemia in alcoholics. A proximal tubular dysfunction seems to be responsible for the reduced TmPO4/GFR. Liver function impairment is not required for the expression of this tubular dysfunction.

Urinary excretion of enzymes in cirrhotics with renal failure

We studied the significance of urinary enzyme measurements in diagnosing proximal tubular damage in cirrhosis of the liver. Urinary excretion (u-enzyme) and fractional urinary excretion (FEenzyme) of gamma-glutamyltranspeptidase (GGT), leucine aminopeptidase (LAP), alkaline phosphatase (AP) and beta-glucuronidase (B-GLU) were quantified in 14 control subjects (group I), 12 cirrhotics with functional renal failure (group II), 13 cirrhotics with renal tubular damage (group III) and 7 non-liver patients with renal tubular damage (group IV). Urinary enzyme excretion and fractional enzyme excretion were significantly higher in the cirrhotics of group III than in the controls or group II. In group III, these tests usually reached values within the range of group IV. The sensitivity of urinary enzyme excretion was 0.92 and specificity ranged from 0.75 (u-LAP) to 1 (u-GGT; u-B-GLU). The sensitivity of fractional enzyme excretion was between 0.61 (FEB-GLU) and 0.84 (FEGGT; FELAP), while specificity was from 0.91 (FELAP; FEAP) to 1 (FEGGT; FEB-GLU). The results indicate that measurement of urinary enzymes may be very useful in diagnosing renal tubular damage in cirrhotic patients with impaired renal function.

Lack of correlation between endotoxaemia and renal hypoperfusion in cirrhotics without overt renal failure

Renal involvement in patients with liver cirrhosis is characterized by renal vasoconstriction, the aetiology of which remains obscure. Endotoxaemia, frequently found in patients with liver cirrhosis and renal failure, has been emphasized as a pathogenic factor. In fifty-seven patients with liver cirrhosis without overt renal failure endotoxin plasma level (Limulus Lysate test), mean renal blood flow (MRBF) (133Xe washout technique), and effective renal plasma flow (ERPF) (p-aminohippurate clearance) were determined. MRBF was decreased in nineteen out of twenty-seven patients, averaging 1.88 +/- 0.51 ml g-1 min-1 (in fourteen controls 3.17 +/- 0.51 ml g-1 ml-1). ERPF was decreased in seventeen out of thirty patients, averaging 380 +/- 164 ml/min (in eighteen controls 624 +/- 127 ml/min). Systemic endotoxaemia was found in sixteen out of fifty-seven patients, levels ranging from 0.62 to 200 ng/ml. No significant difference in renal blood flow values was found between patients with and without endotoxaemia (MRBF = 1.78 +/- 0.51 and 1.93 +/- 0.52 ml g-1 min-1 respectively; ERPF = 429 +/- 119 and 365 +/- 175 ml/min respectively). No significant difference in the frequency of endotoxaemia was found between patients with impaired and unimpaired renal blood flow. Moreover no relation was found between endotoxin plasma levels and MRBF and ERPF respectively. In conclusion in patients with cirrhosis without overt renal failure renal vasoconstriction does not seem to be related to endotoxaemia.