Loss of tubuloglomerular feedback in decompensated liver cirrhosis: physiopathological implications

[Chronic kidney injury in patients with liver diseases - Reappraising pathophysiology and treatment options]

Acute and chronic kidney disease concurs commonly with liver disease and is associated with a wide array of complications including dialysis dependency and increased mortality. Patients with liver disease or liver cirrhosis show a higher prevalence of chronic kidney disease. This is attributed to concomitant comorbidities, such as metabolic syndrome, chronic inflammation, hypercoagulability, hyperfibrinolysis, diabetes mellitus and dyslipidaemias. But chronic progressive kidney disease is not always due to hepatorenal syndrome. Beyond that, other diseases or disease entities should be considered. Among them are diabetic nephropathy, secondary IgA nephropathy, hepatitis C -associated membranoproliferative Glomerulonephritis (MPGN) and hepatitis B-associated membranous nephropathy.Coexisting diseases, similar underlying pathophysiologic mechanisms, or simultaneously concurring pathophysiological processes and overlapping clinical manifestations, impede the etiologic diagnosis and corresponding treatment of chronic kidney disease in the setting of chronic liver disease. In this review, we focus on common and rare pathologies, which can lead to chronic kidney disease in this particular patient group and try to summarize the most recent therapeutic modalities.

Review article: advances in the management of patients with cirrhosis and portal hypertension-related renal dysfunction

BACKGROUND

In cirrhosis, portal hypertension is associated with a spectrum of renal dysfunction that has significant implications for morbidity and mortality.

AIM

To discuss recent progress in the patho-physiological mechanisms and therapeutic options for portal hypertension-related renal dysfunction.

METHODS

A literature search using Pubmed was performed.

RESULTS

Portal hypertension-related renal dysfunction occurs in the setting of marked neuro-humoral and circulatory derangement. A systemic inflammatory response is a pathogenetic factor in advanced disease. Such physiological changes render the individual vulnerable to further deterioration of renal function. Patients are primed to develop acute kidney injury when exposed to additional 'hits', such as sepsis. Recent progress has been made regarding our understanding of the aetiopathogenesis. However, treatment options once hepatorenal syndrome develops are limited, and prognosis remains poor. Various strategies to prevent acute kidney injury are suggested.

CONCLUSION

Prevention of acute kidney injury in high risk patients with cirrhosis and portal hypertension-related renal dysfunction should be a clinical priority.

Acute kidney injury in patients with cirrhosis: perils and promise

A 62-year-old man with cirrhosis secondary to hepatitis C and chronic alcohol abuse was admitted to the intensive care unit with hematemesis and mental status changes. Physical examination showed ascites and stigmata of chronic liver disease. Blood pressure was noted as 87/42 mm Hg and laboratory studies showed a serum creatinine level of 0.8 mg/dL, an estimated glomerular filtration rate of 84 mL/min/1.73 m(2) calculated using the Modification of Diet in Renal Disease Study equation, a serum sodium level of 123 mEq/L, a total serum bilirubin level of 4.3 mg/dL, and an international normalization ratio of 1.6. The patient was resuscitated with packed red blood cells and fresh-frozen plasma and bleeding was controlled. However, on the third day of admission, creatinine level increased to 1.5 mg/dL. Examination of urine sediment showed 1 to 5 bilirubin-stained granular casts per high-powered field and a few renal tubular epithelial cells. The urine sodium level was 21 mEq/L and the fractional excretion of sodium was 0.43%.

Association of AKI with mortality and complications in hospitalized patients with cirrhosis

Acute kidney injury (AKI) is a common and devastating complication in patients with cirrhosis. However, the definitions of AKI employed in studies involving patients with cirrhosis have not been standardized, lack sensitivity, and are often limited to narrow clinical settings. We conducted a multicenter, prospective observational cohort study of patients with cirrhosis and AKI, drawn from multiple hospital wards, utilizing the modern acute kidney injury network (AKIN) definition and assessed the association between AKI severity and progression with in-hospital mortality. Of the 192 patients who were enrolled and included in the study, 85 (44%) progressed to a higher AKIN stage after initially fulfilling AKI criteria. Patients achieved a peak severity of AKIN stage 1, 26%, stage 2, 24%, and stage 3, 49%. The incidence of mortality, general medical events (bacteremia, pneumonia, urinary tract infection), and cirrhosis-specific complications (ascites, encephalopathy, spontaneous bacterial peritonitis) increased with severity of AKI. Progression was significantly more common and peak AKI stage higher in nonsurvivors than survivors (P < 0.0001). After adjusting for baseline renal function, demographics, and critical hospital- and cirrhosis-associated variables, progression of AKI was independently associated with mortality (adjusted odds ratio = 3.8, 95% confidence interval 1.3-11.1).

CONCLUSION

AKI, as defined by AKIN criteria, in patients with cirrhosis is frequently progressive and severe and is independently associated with mortality in a stage-dependent fashion. Methods for earlier diagnosis of AKI and its progression may result in improved outcomes by facilitating targeted and timely treatment of AKI.

Renal effects of the novel selective adenosine A1 receptor blocker SLV329 in experimental liver cirrhosis in rats

Liver cirrhosis is often complicated by an impaired renal excretion of water and sodium. Diuretics tend to further deteriorate renal function. It is unknown whether chronic selective adenosine A(1) receptor blockade, via inhibition of the hepatorenal reflex and the tubuloglomerular feedback, might exert diuretic and natriuretic effects without a reduction of the glomerular filtration rate. In healthy animals intravenous treatment with the novel A(1) receptor antagonist SLV329 resulted in a strong dose-dependent diuretic (up to 3.4-fold) and natriuretic (up to 13.5-fold) effect without affecting creatinine clearance. Male Wistar rats with thioacetamide-induced liver cirrhosis received SLV329, vehicle or furosemide for 12 weeks. The creatinine clearance of cirrhotic animals decreased significantly (-36.5%, p<0.05), especially in those receiving furosemide (-41.9%, p<0.01). SLV329 was able to prevent this decline of creatinine clearance. Mortality was significantly lower in cirrhotic animals treated with SLV329 in comparison to animals treated with furosemide (17% vs. 54%, p<0.05). SLV329 did not relevantly influence the degree of liver fibrosis, kidney histology or expression of hepatic or renal adenosine receptors. In conclusion, chronic treatment with SLV329 prevented the decrease of creatinine clearance in a rat model of liver cirrhosis. Further studies will have to establish whether adenosine A(1) receptor antagonists are clinically beneficial at different stages of liver cirrhosis.

Toward the optimal clinical use of the fraction excretion of solutes in oliguric azotemia

While the fractional excretion of solutes have long been considered excellent research tools to investigate tubular physiology, their clinical use has become common over the last 40 years in the diagnoses of many disorders; however, none have reached the clinical utility of the fractional excretion of sodium in the ability to distinguish pre-renal azotemia from acute tubular necrosis. Nevertheless, there are many drugs and medical conditions that interfere with that utility and recently other solutes, including urea, uric acid and lithium, have been recently investigated to improve the diagnostic ability in clinical situations where the fractional excretion of sodium is known to be unreliable. We review the tubular physiology of these solutes and show how the differences in tubular physiology might be exploited to develop a strategy for their optimal clinical use.

Role of sodium during formation of edema in children with nephrotic syndrome

BACKGROUND

The pathogenesis of edema in nephrotic syndrome is not entirely understood. The aim of this study was to contribute to the discussion on edema pathogenesis in nephrotic syndrome by following changes in volume and sodium retention for the course of the disease in children with steroid-sensitive nephrotic syndrome (SSNS).

METHODS

Forty-one children with SSNS were included in the study. The patients were divided into three groups (group I: relapse-edematous; group II: relapse-edema free; group III: remission). We investigated the value of the significance and area of sodium retention and vasoactive hormones. In addition, we measured parameters such as inferior vena cava collapsibility index, left atrium diameter, and total body water (TBW) to determine the volume load and cause of edema in children with SSNS.

RESULTS

TBW increased in the relapse-nephrotic syndrome group and the difference was statistically significant among groups (P < 0.001). However, inferior vena cava collapsibility index and left atrium diameter were not different among groups. Fractional sodium excretion was lower in children with relapse nephrotic syndrome (P < 0.05).

CONCLUSION

Although TBW increases in children with SSNS, intravascular volume is normal. In addition, hypoalbuminemia and sodium retention of the proximal tubule cause edema in children with SSNS.

Research progress in the mechanism of renal vasoconstriction in hepatorenal syndrome

Hepatorenal syndrome (HRS) is defined as the development of renal failure in patients with severe liver disease in the absence of any other identifiable cause of renal pathology. The hallmark of HRS is renal vasoconstriction. The cause of renal vasoconstriction may involve several factors: activation of renal nervous system, imbalance of renal vasoactive mediators and molecular mechanism. In this review, we summarize the above progress.