Spectrum of renal tubular damage in renal failure secondary to cirrhosis and fulminant hepatic failure

Pathophysiology of Hepatorenal Syndrome

Hepatorenal syndrome type 1 (HRS-1) is a unique form of acute kidney injury that affects individuals with decompensated cirrhosis with ascites. The primary mechanism leading to reduction of kidney function in HRS-1 is hemodynamic in nature. Cumulative evidence points to a cascade of events that led to a profound reduction in kidney perfusion. A state of increased intrahepatic vascular resistance characteristic of advanced cirrhosis and portal hypertension is accompanied by maladaptive peripheral arterial vasodilation and reduction in systemic vascular resistance and mean arterial pressure. As a result of a fall in effective arterial blood volume, there is a compensatory activation of the sympathetic nervous system and the renin-angiotensin system, local renal vasoconstriction, loss of renal autoregulation, decrease in renal blood flow, and ultimately a fall in glomerular filtration rate. Systemic release of nitric oxide stimulated by the fibrotic liver, bacterial translocation, and inflammation constitute key components of the pathogenesis. While angiotensin II and noradrenaline remain the critical mediators of renal arterial and arteriolar vasoconstriction, other novel molecules have been recently implicated. Although the above-described mechanistic pathway remains the backbone of the pathogenesis of HRS-1, other noxious elements may be present in advanced cirrhosis and likely contribute to the renal impairment. Direct liver-kidney crosstalk via the hepatorenal sympathetic reflex can further reduce renal blood flow independently of the systemic derangements. Tense ascites may lead to intraabdominal hypertension and abdominal compartment syndrome. Cardio-hemodynamic processes have also been increasingly recognized. Porto-pulmonary hypertension, cirrhotic cardiomyopathy, and abdominal compartment syndrome may lead to renal congestion and complicate the course of HRS-1. In addition, a degree of ischemic or toxic (cholemic) tubular injury may overlap with the underlying circulatory dysfunction and further exacerbate the course of acute kidney injury. Improving our understanding of the pathogenesis of HRS-1 may lead to improvements in therapeutic options for this seriously ill population.

Acid-Base and Potassium Disorders in Liver Disease

Acid-base and potassium disorders occur frequently in the setting of liver disease. As the liver's metabolic function worsens, particularly in the setting of renal dysfunction, hemodynamic compromise, and hepatic encephalopathy, acid-base disorders ensue. The most common acid-base disorder is respiratory alkalosis. Metabolic acidosis alone or in combination with respiratory alkalosis also is common. Acid-base disorders in patients with liver disease are complex. The urine anion gap may help to distinguish between chronic respiratory alkalosis and hyperchloremic metabolic acidosis when a blood gas is not available. A negative urine anion gap helps to rule out chronic respiratory alkalosis. In this disorder a positive urine anion gap is expected owing to suppressed urinary acidification. Distal renal tubular acidosis occurs in autoimmune liver disease such as primary biliary cirrhosis, but often is a functional defect from impaired distal sodium delivery. Potassium disorders are often the result of the therapies used to treat advanced liver disease.

The effects of desferrioxamine and quercetin on hepatic ischemia-reperfusion induced renal disturbance

BACKGROUND

The aim of this study was to analyze the effects of 45min of hepatic ischemia and 1h of reperfusion on renal oxidative stress parameters, on renal tissue damage, and the role of Desferrioxamin (Dfx) and Q on these parameters.

METHODS

Thirty Wistar albino rats were randomized to five groups. Group I was the control group. Group II received no treatment. Groups III and IV received intramuscular injections of desferrioxamine (100mg/kg) and quercetin (50mg/kg), respectively. Group V was administered Dfx and quercetin in combination. After treatment for 3 days, groups II, III, IV, and V were exposed to total hepatic ischemia for 45min. Plasma alanine aminotransferase levels, renal malondialdehyde and reduced glutathione (GSH) activities were measured after reperfusion for 1h. Histopathological and ultrastructural analysis of renal tissues was carried out.

RESULTS

Plasma creatinine and BUN levels were markedly increased in the IR group and pretreated groups. Kidney MDA increased in the IR group, Q and Dfx+Q significantly decreased kidney MDA Kidney GSH levels markedly decreased in the IR group, Dfx significantly increased kidney GSH. No evidence of overt injury was observed in any renal tissue under light and electron microscopy.

CONCLUSIONS

Our data demonstrated that 45min of hepatic ischemia and 1h of reperfusion may alter renal functions and may cause oxidative stress on renal tissue. Q and Dfx seem to have a beneficial effect via the GSH system and modulation of MDA levels.

Living donor liver transplantation for children with liver failure and concurrent multiple organ system failure

Liver transplantation for pediatric patients in liver failure and multiple organ system failure (MOSF) often results in poor patient survival. Progression of organ failure occurs while awaiting a cadaveric allograft. Therefore, we considered living donor liver transplantation (LDLT) in this critically ill group of children and report our initial results with comparison to a similar group who received cadaveric donation (CAD). A retrospective chart review was performed on all pediatric liver transplant recipients who met criteria for MOSF at the time of transplantation. Data collection involved pretransplantation patient profiles, as well as postoperative complications and patient survival. Eight patients in MOSF received living donor transplants and 11 patients received a cadaveric allograft. Mean wait time was 3.5 days in the LDLT group and 6.5 days in the CAD group. Pretransplantation patient profiles and postoperative complications were similar between groups. Mean cold ischemia times were 3.8 hours in the LDLT group and 7.9 hours in the CAD group (P = .0002). Thirty-day and 6-month survival rates of the LDLT group were 88% and 63% compared with 45% and 27% in the CAD group, respectively. Living donor transplant recipients in MOSF had decreased wait times to transplantation, as well as decreased cold ischemia times, compared with cadaveric transplant recipients. Patients in the LDLT group had markedly improved survival compared with the CAD group. Timely transplantation before worsening organ failure may account for these findings.

The hepatorenal syndrome

Hepatorenal syndrome may occur in any form of severe liver disease. It appears less common in children than adults, but still carries a poor prognosis. There are several factors involved in its aetiology, including a decreased renal perfusion pressure, activation of the renal sympathetic nervous system and increased synthesis of several vasoactive mediators, which may modulate glomerular filtration by acting as both renal vasoconstrictors and dynamic regulators of the glomerular capillary ultrafiltration coefficient, through their action on mesangial cells. This review will discuss the pathophysiology of the hepatorenal syndrome and some of the principles of management of patients with renal failure and severe liver disease. The role of renal support and liver transplantation will also be covered.

Endotoxin-induced acute tubular necrosis in cirrhotic rats

In order to clarify the role of endotoxin in acute tubular necrosis in liver cirrhosis, lipopolysaccharide (LPS) was injected to rats with liver injury with exposure to carbon tetrachloride (CCl4) inhalation. Rats showed liver cirrhosis with ascites retention after 10 weeks' CCl4 treatment and liver fibrosis after 6 weeks' CCl4 treatment. Histopathological grading of kidney injuries after LPS treatment was more severe either in cirrhotic rats or in liver fibrotic rats than in normal rats. All cirrhotic rats had severe acute tubular necrosis after either dose of LPS, but only small necrotic foci of tubuli were seen in a few normal and liver fibrotic rats. The results indicate that endotoxin, which overflows due to disturbance of inactivation in the cirrhotic liver, may contribute to acute tubular necrosis. This effect of endotoxin is supposed to be a direct hemodynamic damage.

The distribution of 3H-labeled endotoxin in the kidney of liver cirrhotic rats

Although the etiology and pathogenesis of progressive renal failure is largely unknown, endotoxin is supposed to be one of the contributory factors. However, the distribution of endotoxin in liver cirrhosis has not been clarified. Therefore we studied the distribution of 3H-labeled endotoxin in the kidney in rats with CCl4-induced liver injury. Daily inhalations of CCl4 on rats for 6 and 10 weeks produced liver fibrosis (LF group, N = 5) and cirrhosis (LC group, N = 5), respectively. At 6 or 10 weeks, animals were sacrificed 24 hours after an intravenous injection of endotoxin labeled with 3H at the galactose moiety (12,000 cpm/1 g body weight). In the liver, 3H-labeled endotoxin was taken up mainly by Kupffer cells as determined by autoradiography. Compared to control rats, in rats of the LC or LF group the measured amount of 3H-labeled endotoxin per gram kidney or ml blood increased, while that of the liver was significantly decreased. A positive correlation of the amount of 3H-labeled endotoxin per weight or volume respectively was shown between kidney and blood, but not between lung or spleen and blood. These results suggest that overflow of endotoxin due to decreased inactivation in the liver causes endotoxemia in liver injury and that the resulting endotoxemia may directly affect the kidney. The resulting endotoxin-induced vasoconstriction may be a contributory factor for the progressive renal failure frequently observed in liver cirrhosis.

Investigation of the renal injury caused by liver ischemia-reperfusion in rats

To explain the mechanism of renal injury caused by liver ischemia-reperfusion, we investigated biochemical and morphological changes in the liver and kidney in rats. After reperfusion following 60 min of liver ischemia, numerous changes were found. The level of serum transaminases and lipid peroxide formation in the liver tissue increased significantly. Electron microscopic studies revealed that most of the hepatocytes had swollen mitochondria and clumping of the nuclear chromatin. The sinusoidal endothelium was disrupted and the sinusoidal lumen was filled with numerous erythrocytes. Blood endotoxin concentration, plasma lipid peroxide levels, and serum beta-glucuronidase activities were significantly higher than in the control group. Biochemical and morphological renal injury was also observed. Tissue lipid peroxide levels increased in both the kidney and the liver. Microscopic examination revealed damage to the renal tubules, including interstitial edema, dilatation of the lumen, and granular casts derived from necrotic cells in the proximal convoluted tubule. The levels of urinary N-acetyl-beta-D-glucosaminidase (NAG) in the liver ischemia-reperfusion group were also higher than in the control group. These results suggest that the renal injury was caused by an increase in endotoxin, lipid peroxide, and lysosomal enzymes in the blood following the liver injury induced by the ischemia-reperfusion.

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.

A study of the mechanisms of proteinuria in nephritis and chronic renal failure

This study was carried out on 50 patients suffering from renal disorders; 30 nephritis patients and 20 chronic renal failure patients. Twenty-four healthy persons were used as a control group. In order to cast some light on the degree of the impaired glomerular permeability with respect to the blood proteins, selectivity of proteinuria was assessed by means of the clearance of albumin, ceruloplasmin, transferrin, and haptoglobin. Disturbances in the metabolism of these proteins were observed and discussed in light of the proteinuria selectivity index. The demonstration of the selective proteinuria in the presence of haptoglobin was concluded to be indicative of the degree of impaired glomerular permeability in nephritis and chronic renal failure.

Analysis of serum and urinary retinol binding protein in hepato-renal syndrome

Retinol binding protein (RBP) was analyzed in the sera and urines of 5 patients with hepato-renal syndrome (HRS), 4 with acute tubular necrosis (ATN), 20 liver cirrhosis patients with normal kidney function (NKF), 14 chronic renal failure (CRF) patients, and 19 healthy adults. All renal failure patients had high mean urine RBP (URBP): HRS, 8 mg/L; ATN, 11 mg/L; CRF, 8 mg/L respectively; p less than 0.001 vs the rest. Those with ATN and CRF had high mean serum RPB (SRBP): 146 and 149 mg/L, respectively, p less than 0.001 compared to the other groups. In HRS, in spite of renal failure, SRBP was very low (mean = 12 mg/L). The cirrhotics with NKF averaged less than 50% of the SRBP values of the healthy controls (16 vs 41 mg/L RBP, p less than 0.001); their RBP excretion was normal (mean URBP of 0.1 vs 0.06 mg/L in the control group). RBP analyses before and during HRS in two patients showed a marked increase in urine RBP during HRS (35- and 600-fold respectively) with practically unchanged serum levels. Impaired hepatic production and/or release is proposed to explain the low serum RBP in HRS, and a renal tubular injury or dysfunction to account for its high excretion. The RBP urinary loss could further compromise an already abnormal RBP metabolism and its serum levels. This combination (of low serum and high urine RBP), in the context of renal failure occurring in alcoholic liver cirrhosis, could help in the recognition of HRS.

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.

Tubular dysfunction in the deeply jaundiced patient with hepatorenal syndrome

We examined beta 2-microglobulin (B2MG) excretion, an index of tubular function, in patients with hepatorenal syndrome, in whom tubular function is generally regarded as normal. Urine B2MG was significantly higher in these patients than in control patients with normal serum creatinine concentration. Patients with high urine B2MG concentration had markedly higher serum bilirubin than did patients with normal values (31 +/- 3 vs. 10 +/- 8 mg%, p less than 0.001), whereas prothrombin activity, serum albumin and serum B2MG concentration were similar. A "threshold" serum bilirubin concentration of about 23 mg% differentiated patients with normal and high urine B2MG values. Renal morphology at autopsy was unremarkable in both groups. Tubular dysfunction, manifested by increased urinary excretion of B2MG, occurs in patients with hepatorenal syndrome and deep jaundice. This measurement cannot, therefore, be used to make a diagnosis of acute tubular injury, as due to aminoglycosides, in such patients.

Determination of lysozyme in serum, urine, cerebrospinal fluid and feces by enzyme immunoassay

Conjugates of human lysozyme and horseradish peroxidase (HRP) were prepared by means of the heterobifunctional reagent N-succinimidyl 3-(2-pyridyldithio) propionate. A conjugate containing 2 mol HRP/mol lysozyme was isolated by gel filtration and used as a labeled antigen in competitive enzyme immunoassays, in which anti-lysozyme rabbit IgG had been bound to wells of microtiter plates. The assay can detect as little as 1 microgram lysozyme/l. The following reference intervals have been established: 950-2450 micrograms/l for serum, 1.7-123 micrograms/l for urine, 17.6-118 micrograms/l for cerebrospinal fluid and 0.04-1.5 microgram/g for feces.

Glomerular tubular reflux--a morphologic renal lesion associated with the hepatorenal syndrome

The hepatorenal syndrome, a primary cause of death from acute and chronic liver disease, consists of a functional renal failure whereby examination of the kidney has previously shown no distinct or specific morphologic change. We describe an unusual renal lesion consisting of the reflux of proximal convoluted tubular epithelium into Bowman's space. An autopsy series shows this glomerular change to be present in 71.4% of cases with the hepatorenal syndrome, while only present in 0 to 27.3% in other autopsy categories (p less than 0.001). Since this lesion has been previously described with experimental renal ischemic change and terminal hypotension, it is possible that it is caused in part by the decreased or altered renal blood flow known to be associated with the hepatorenal syndrome.

Turbidimetric determination of lysozyme with Micrococcus lysodeikticus cells: reexamination of reaction conditions

Factors affecting the activity of human lysozyme (EC 3.2.1.17) toward cell suspensions of Micrococcus lysodeikticus were reexamined. Effects of substrate concentration, pH, and ionic strength and matrix effects of protein were assessed with special emphasis on the interdependence of various parameters. On the basis of these evaluations, an optimized kinetic turbidimetric method for lysozyme assay was set up. The method was applied for automation with a System Olli 3000 analyzer. The new automated lysozyme assay proved good for routine clinical use in regard to analysis speed, sensitivity, linearity, and reproducibility. Reference values for serum, urinary, and cerebrospinal fluid lysozyme were assessed with the automated method.

Acute tubular necrosis in hepatorenal syndrome: an electron microscopy study

This report describes light and transmission electron microscopy (LM and EM, respectively) studies of kidneys from five cases of hepatorenal syndrome. The kidneys were removed and fixed for LM and EM between 30 and 120 min after death. All patients had progressive renal failure after admission to the hospital. All cases were jaundiced, had ascites, and exhibited features of hepatic encephalopathy. LM study revealed severe acute tubular lesions (ATL) or, more conventionally, acute tubular necrosis (ATN). EM study demonstrated necrosis of the proximal tubules characterized by swelling, disorganization of the cristae and appearance of dark bodies in the mitochondria, coalescence, fragmentation or displacement of the microvilli, loss of plasma membranes, rupture of the basement membranes, and separation of the cells from the basement membranes. Rupture of tubular basement membranes (tubulorrhexis) and mitochondrial dark bodies suggest an ATN due to ischemia or induced by vasoconstrictor substance(s). Glomerular lesions were infrequent (one in five) and therefore, do not seem to have contributed to renal failure. All cases terminally had extremely low urinary sodium (11 mEq/liter), high urinary potassium (50 mEq/liter), a remarkably low urinary sodium/potassium ratio (0.26, normal = 4.27), and a low urinary osmolality (less than 400 mOsm/kg). From this study we conclude that an ATN of variable severity may be associated with the hepatorenal syndrome. Since this ATN developed without preceding shock, sepsis, or hypotension it is possible that this ATN like that in ischemic acute renal failure may be due to reduced renal blood flow and intense cortical vasoconstriction which has been reported in hepatorenal syndrome. Finally, our data imply that low urinary sodium is consistent with this pathologic lesion in this clinical setting.

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

To assess the renal tubular damage in liver cirrhosis the fractional clearances of beta-2-microglobulin (B2m-fr.cl) and malate-dehydrogenase (MDH-fr.cl) were measured respectively in sixty-four and in forty-six out of seventy-nine patients with liver cirrhosis of different aetiology; furthermore the fractional excretions of gammaglutamyl-transpeptidase (fr-GGT) and of alpha-glucosidase (fr-AGL) were determined in fifty-three and in forty of them respectively. In all patients glomerular filtration rate (GFR) and renal plasma flow (RPF) were also measured. Twenty-five subjects were studied as a control group for the enzyme excretions, sixteen for B2m-fr.cl. B2m-fr.cl and MDH-fr.cl--indexes of tubular functions--on the average were normal and only slightly increased respectively in cirrhotics compared to controls. Nevertheless fr-GGT and fr-AGL--indexes of cytolysis of tubular cells--on the average were massively increased in cirrhosis compared to controls, particularly in those with reduced RPF and/or GFR. No clear relationship between the indexes of tubular damage studied and the indexes of liver function was found. Our results show that (1) A renal tubular anatomical damage was found by means of an increase in the release of enzyme from tubular cells in patients with liver cirrhosis, particularly in those with a significant reduction of RPF and/or GFR; even so renal reabsorption of low molecular weight proteins is generally maintained. (2) The tubular damage does not seem to be related to the degree of liver impairment.

Renin-angiotensin-aldosterone system in cirrhosis

According to traditional concepts, ascites formation and portal hypertension in cirrhosis lead to a deficit in the 'effective' extracellular fluid (ECF) and blood volumes respectively. The renin-angiotensin-aldosterone (RAA) system is thus stimulated and the kidneys retain fluid as a homeostatic mechanism to restore the ECF and blood volumes. Recent studies, however, show that approximately two-thirds of patients with ascites do not have a stimulated RAA system and in those without clinical evidence of fluid retention the RAA system is actually suppressed. These findings are incompatible with the concepts of reduced effective ECF and blood volumes. Despite the fact that most patients retaining sodim and accumulating ascites have a normal plasma aldosterone concentration, other evidence strongly suggests a dominant role for aldosterone in the regulation of renal sodium excretion. There might therefore be an increased renal tubular sensitivity to aldosterone in cirrhosis. For the one-third of patients with ascites who do have a stimulated RAA system this may well be a response to reduced effective ECF and/or blood volumes in accord with traditional concepts.