Renal response to a saline load in well-compensated alcoholic cirrhosis

Lipoprotein profile of pleural and peritoneal transudates in dogs and cats

BACKGROUND

Current diagnostic evaluation of transudative effusions rarely aids in identifying an underlying etiology. Lipoproteins in the fluid might reflect the site or nature of vessel involvement.

OBJECTIVES

Improve the classification and diagnostic utility of pleural and peritoneal transudates in dogs and cats by investigating lipoprotein patterns in effusions. Compare these patterns with other peritonaeal and pleural fluid variables and underlying diseases.

ANIMALS

Samples of transudates and serum from 18 cats and 37 dogs with transudative effusion (total nucleated cell count [TNCC] <5000 cells/μL) were analyzed.

METHODS

Lipoprotein fractions, triglyceride, and cholesterol (CHO) concentrations were prospectively determined in paired fluid and serum samples. Standard fluid measurements were retrospectively collected.

RESULTS

Two distinct fluid lipoprotein patterns were noted. Fluids rich in VLDL+IDL were associated with chronic kidney disease, acquired portosystemic shunts or protein-losing enteropathy (group I). Fluids rich in denser lipoproteins were associated with underlying heart disease, caudal vena cava syndrome or intracavitary neoplasia (group II). Group I and group II also had significant differences between fluid concentrations of CHO (x̄ = 8 vs 110 mg/dL) and TP (x̄ = 0.6 vs 3.8 g/dL), respectively. Five peritoneal transudates were triglyceride-rich (>100 mg/dL) and associated with pancreatitis.

CONCLUSIONS AND CLINICAL IMPORTANCE

Protein-poor (TP <1.5 g/dL) and protein-rich (TP >2.5 g/dL) transudates were associated with distinct lipoprotein patterns and specific groups of disease. Effusions secondary to pancreatitis might be transudative and rich in triglycerides.

Murine epithelial sodium (Na+) channel regulation by biliary factors

The epithelial sodium channel (ENaC) mediates Na+ transport in several epithelia, including the aldosterone-sensitive distal nephron, distal colon, and biliary epithelium. Numerous factors regulate ENaC activity, including extracellular ligands, post-translational modifications, and membrane-resident lipids. However, ENaC regulation by bile acids and conjugated bilirubin, metabolites that are abundant in the biliary tree and intestinal tract and are sometimes elevated in the urine of individuals with advanced liver disease, remains poorly understood. Here, using a Xenopus oocyte-based system to express and functionally study ENaC, we found that, depending on the bile acid used, bile acids both activate and inhibit mouse ENaC. Whether bile acids were activating or inhibiting was contingent on the position and orientation of specific bile acid moieties. For example, a hydroxyl group at the 12-position and facing the hydrophilic side (12α-OH) was activating. Taurine-conjugated bile acids, which have reduced membrane permeability, affected ENaC activity more strongly than did their more membrane-permeant unconjugated counterparts, suggesting that bile acids regulate ENaC extracellularly. Bile acid-dependent activation was enhanced by amino acid substitutions in ENaC that depress open probability and was precluded by proteolytic cleavage that increases open probability, consistent with an effect of bile acids on ENaC open probability. Bile acids also regulated ENaC in a cortical collecting duct cell line, mirroring the results in Xenopus oocytes. We also show that bilirubin conjugates activate ENaC. These results indicate that ENaC responds to compounds abundant in bile and that their ability to regulate this channel depends on the presence of specific functional groups.

Long-term clinical outcome of patients with cirrhosis and refractory ascites treated with transjugular intrahepatic portosystemic shunt insertion

BACKGROUND AND AIM

Transjugular intrahepatic portosystemic shunt (TIPS) is indicated for the treatment of refractory ascites in cirrhosis. The long-term outcome of TIPS for refractory ascites is unknown. The aim of this study is to describe the natural history of patients with refractory ascites post-TIPS, and compare between polytetrafluoroethylene (PTFE)-covered versus bare stents.

METHODS

A retrospective chart review of patients who had TIPS for refractory ascites was conducted. Prospectively collected data include demographics, angiographic data, blood work, and urinary sodium excretion.

RESULTS

There were 136 patients who received TIPS (bare = 104, covered = 32) for over 22 years. Patients with PTFE stents had lower international normalized ratio and model for end-stage liver disease score. More patients with bare stents developed shunt dysfunction (74.0% vs 24.1%, P < 0.0001) and required more TIPS revisions (1.6 ± 0.2/patient vs 0.2 ± 0.1, P < 0.0001). Urinary sodium excretion increased significantly from first month and progressed to 98 ± 9 mmol/day at 12th month post-TIPS (P < 0.001 vs baseline), concurrent with improved renal function. Most patients (77.6%) completely cleared the ascites without diuretics, but many achieved this beyond 2 years. Number of TIPS revision was predictive of complete response at 12 months (odds ratio [OR] 0.7, 95% confidence interval [CI] 0.5-0.9, P < 0.05). Age (hazard ratio [HR] = 1.05 [95% CI 1.02-1.08], P < 0.01), complete response (HR = 0.22 [95% CI 0.12-0.40], P < 0.0001) and polytetrafluoroethylene stents (HR = 0.23 [95% CI 0.05-0.97], P < 0.05) were predictive of survival.

CONCLUSION

TIPS is an effective treatment for cirrhotic refractory ascites. Ascites clearance is dependent on number of TIPS revision, whereas survival is predicted by younger age, complete response, and covered stent use, although era effect likely contributed to improved survival with covered stent use.

Calcium-dependent diuretic system in preascitic liver cirrhosis

BACKGROUND & AIMS

Extracellular Ca(++) activates cell membrane calcium-sensing receptors (CaRs), leading to renal tubule production of prostaglandins E(2) (PGE(2)), which decrease both sodium reabsorption in the thick ascending limb of Henle's loop and free-water reabsorption in collecting ducts.

AIMS & METHODS

To assess the activity of this diuretic system in experimental cirrhosis, we evaluated renal function, hormonal status, PGE(2) urinary excretion, and renal tissue concentrations of Na(+)-K(+)-2Cl(-) co-transporters (BSC-1) and CaRs in three groups of rats: one group of controls receiving 5% glucose solution (vehicle) intravenously and two groups of rats with CCl(4)-induced preascitic cirrhosis receiving either vehicle or 0.5mg i.v. Poly-l-Arginine (PolyAg), a CaR-selective agonist.

RESULTS

Compared to controls, cirrhotic rats showed reduced urine volume and sodium excretion (p<0.05). Western blot analysis revealed reduced CaRs and increased BSC-1 protein content in kidneys of cirrhotic rats compared with controls (all p<0.01). PolyAg-treated cirrhotic rats had their urine and sodium excretion returned to normal; PolyAg also increased renal plasma flow, PGE(2) urinary excretion, and free-water clearance in cirrhotic rats (all p<0.01 v. untreated cirrhotic animals).

CONCLUSIONS

In preascitic cirrhosis, sodium retention may be linked to down-regulation of renal CaRs and up-regulation of tubular sodium-retaining channels. Calcimimetic drugs normalize preascitic sodium retention.

Effects of a 7-day treatment with midodrine in non-azotemic cirrhotic patients with and without ascites

BACKGROUND/AIMS

Splanchnic arterial vasodilatation has been causally related with hyperdynamic circulation and impaired natriuresis in advanced cirrhosis and has also been suggested to be responsible for the subtle sodium retention in pre-ascitic cirrhosis. This study evaluated the effects of a 7-day treatment with the alpha1-adrenergic agonist midodrine in non-azotemic cirrhotic patients with and without ascites.

METHODS

Thirty-nine cirrhotic patients were studied at baseline and 7 days after administration of oral midodrine 10mg, t.i.d. (11 without and 12 with ascites) or placebo (8 without and 8 with ascites).

RESULTS

A significant increase in urine sodium excretion was noted after midodrine administration in patients without and with ascites, in line with significant increases in mean arterial pressure and systemic vascular resistance, and significant decreases in cardiac output and heart rate. Significant increases in glomerular filtration rate, filtration fraction, and urine volume and significant decreases in plasma renin activity and aldosterone were observed in patients with ascites. Placebo had no effect in any study group.

CONCLUSIONS

The administration of midodrine for 7 days improves systemic haemodynamics and sodium excretion in non-azotemic cirrhotic patients without or with ascites. In patients with ascites, but not in those without ascites, these effects are associated with a suppression of the activity of the renin-angiotensin-aldosterone system, suggesting that the increase in natriuresis is related to the improvement in the effective arterial blood volume.

A novel sodium overload test predicting ascites decompensation in rats with CCl4-induced cirrhosis

BACKGROUND/AIMS

We aimed to develop a non-invasive test to identify the initial alterations of sodium homeostasis and prospectively predict decompensation in preascitic cirrhotic rats.

METHODS

The sodium overload test (SOT) was performed in control (CT) and CCl4-induced cirrhotic rats (CH) by calculating the percentage of sodium excreted in the urine after NaCl oral administration (0.5 g/kg). Liver fibrosis was quantified by image cytometry.

RESULTS

From the 8th week of CCl4 intoxication, while the daily sodium balance did not change in CH and CT, SOT became significantly lower in the former (62.1+/-13.2 vs 78.8+/-13.2%; P=0.035). At sacrifice, ascites was only present in one animal. The degree of liver fibrosis correlated with SOT. In subsequent experiments, 17 cirrhotic rats developed ascites between the 9th and 14th weeks. SOT remained stable up to 3 weeks before ascites appearance, while it fell significantly to 35+/-19 and 26+/-21% at 2 and 1 week before ascites diagnosis, respectively. Nearly all the rats (95%) with a SOT<60% developed ascites within 3 weeks.

CONCLUSIONS

In preascitic cirrhotic rats, SOT unveils sodium metabolism abnormalities earlier than the daily sodium balance and prospectively predicts ascites appearance, identifying rats in a homogeneous stage of cirrhosis, which is essential in pathophysiological studies on sodium retention.

Loss of tubuloglomerular feedback in decompensated liver cirrhosis: physiopathological implications

In healthy subjects, arterial pressure reduction or renal ischemia produces renal artery dilatation through autoregulation and tubuloglomerular feedback (TuGF). Patients with decompensated cirrhosis have reduced kidney perfusion pressure but show renal vasoconstriction instead of autoregulation-mediated vasodilation. This study investigates the consequences of kidney autoregulation loss on renal perfusion, glomerular filtration rate, and tubular handling of electrolytes in both compensated and ascitic nonazotemic cirrhotic patients. Forty-two consecutive patients with diuretic-free liver cirrhosis (32 with preascitic and 10 with ascitic disease) and 10 controls were submitted to the following determinations: (a) basal plasma renin activity and aldosterone levels; (b) endogenous dopaminergic activity measured as incremental aldosterone responses during metoclopramide administration; and (c) renal clearances of sodium, potassium, inulin, para-aminohippurate and lithium. Compared with the other groups, ascitic patients showed lower renal plasma flow (P < 0.01) and lithium clearance (P < 0.05), a higher filtration fraction (P < 0.01), and secondary aldosteronism. Controls and preascitic patients displayed tubuloglomerular feedback (the mechanism increasing the glomerular filtration rate when a reduced sodium load reaches the distal tubule), as demonstrated by negative correlations between fractional excretion of lithium (an expression of fractional delivery of sodium to the distal nephron) and glomerular filtration rate (respectively, r = -0.73, P < 0.03, and r = -0.48, P < 0.01). Conversely, patients with ascites showed a positive correlation between lithium fractional excretion and glomerular filtration rate (r = 0.64, P < 0.05). Reduction in renal perfusion, increased filtration fraction, and TuGF derangement, as found in decompensated patients, are indicative of prevalent postglomerular arteriolar vasoconstriction, with ensuing stimulation of proximal tubular sodium reabsorption.

Evidence of a dynamic aldosterone-independent distal tubular control of renal sodium excretion in compensated liver cirrhosis

BACKGROUND AND AIM

In preascitic cirrhosis increased sodium retention occurs in kidney distal tubule in spite of normal aldosterone plasma levels. No clearance technique can dissect the respective contribution to sodium retention exerted by Henle's loop, distal convoluted tubule and collecting duct, so we evaluated proximal and distal tubular sodium handling in preascites during two manoeuvres that temporarily increase aldosterone secretion.

METHODS

Ten patients with compensated cirrhosis and nine controls were studied in recumbency, during standing and after dopamine receptor blockade with metoclopramide through: 4 h renal clearances of sodium, potassium, lithium and creatinine; plasma levels of active renin and aldosterone.

RESULTS

Whilst comparable in recumbency, aldosterone levels significantly rose during standing and after metoclopramide in both groups. In patients, dopaminergic blockade caused a fall of distal sodium delivery (P < 0.01) but urinary sodium excretion was unchanged because the reabsorbed fraction of distal sodium delivery also fell (P < 0.03). Cirrhotic patients showed the same findings in the passage from recumbency to standing.

CONCLUSIONS

In preascitic cirrhosis, the distal tubular segments of the nephron are able to cope with decreases in tubular flow by reducing reabsorption at an aldosterone-independent site (possibly the loop of Henle).

Systemic nitric oxide production and renal function in nonazotemic human cirrhosis: a reappraisal

OBJECTIVES

Several studies in human cirrhosis have demonstrated increased nitric oxide (NO) production. In experimental animals, intracerebroventricular administration of NO donors causes a marked depression of the endogenous dopaminergic activity, a function known to be physiologically recruited and exerting a natriuretic function in patients with compensated cirrhosis. The aim of this study is to evaluate the interaction between the systemic plasma levels of NO, the endogenous dopaminergic activity and the main parameters of renal function in patients with liver cirrhosis of differing degrees of severity.

METHODS

A total of 21 patients (11 with preascitic and 10 with nonazotemic diuretic-free ascitic cirrhosis) and 10 healthy control subjects underwent the following tests: a) basal plasma renin activity (PRA) and aldosterone levels; b) renal clearances of sodium, potassium, inulin, para-minohippurate and lithium (the latter being a measure of the fluid delivery to the distal nephron); c) NO systemic plasma levels measured through paramagnetic resonance spectroscopy as nitrosylhemoglobin complexes; d) endogenous dopaminergic activity, evaluated by means of the incremental prolactin and aldosterone plasma levels after dopaminergic blockade with i.v. metoclopramide.

RESULTS

NO plasma values and endogenous dopaminergic activity, although significantly increased with respect to healthy controls, were not different in the two groups of patients. The plasma NO/PRA ratio was significantly higher in the group of compensated patients with respect to ascitic cirrhotics (respectively, 18.3 +/- 11.8 vs 3.5 +/- 2.6 A.U./ng/ml/h, p < 0.001). Compared with compensated cirrhotics, patients with ascites showed significantly lower values of glomerular filtration rate (GFR) and renal plasma flow (RPF). Interestingly, GFR values were substantially the same in the ascitic patients and the control subjects. Compensated patients displayed a significant positive correlation between metoclopramide-induced incremental aldosterone plasma levels (i.e., endogenous dopaminergic tone) and fractional excretion of sodium (r = 0.58; p < 0.05). In the group of compensated patients, NO levels correlated inversely with creatinine plasma concentrations (r = -0.85; p < 0.001) and directly with inulin clearance (r = 0.65; p < 0.05).

CONCLUSIONS

These data show that, at least in compensated cirrhotic patients, the stimulation of systemic NO production and the increased dopaminergic function may be mechanisms preventing renal perfusion, GFR, and fractional excretion of sodium from precocious reductions.

The mechanism of improved sodium homeostasis of low-dose losartan in preascitic cirrhosis

Renal sodium retention on standing is one aspect of the abnormal renal sodium handling in preascitic, well-compensated patients with cirrhosis. Recently, it has been shown that low doses (7.5 mg) of the angiotensin II (Ang II) receptor antagonist, losartan, can reverse renal sodium retention on high, 200-mmol sodium/d diet in these patients and restore them to sodium balance. Therefore, the effect of 7.5 mg of losartan on sodium excretion, when changing from supine to erect posture for 2 hours, was examined in 10 well-compensated patients with cirrhosis and 9 age- and sex-matched controls on the same sodium diet, under strictly controlled metabolic conditions. In contrast to control subjects, in whom sodium excretion was unaffected, single 7.5-mg doses of losartan again restored the preascitic patients with cirrhosis to sodium balance. In addition, it blunted the fall in erect posture- induced renal sodium excretion by a reduction in proximal and distal tubular reabsorption of sodium. These changes occurred without any significant changes in blood volumes, systemic and renal hemodynamics, or glomerular filtration rate (GFR) and filtered sodium load compared with controls, and despite activation of the systemic renin-angiotensin-aldosterone system, which was still within normal levels. In conclusion, the beneficial natriuretic effects of low-dose losartan on erect posture - induced sodium retention in preascitic cirrhosis supports the suggestion that the pathophysiology of sodium retention in preascites is in part caused by an intrarenal tubular effect of Ang II in that posture.

The pathophysiologic basis for the treatment of cirrhotic ascites

Advances in the understanding of the pathophysiology of sodium retention and ascites formation in cirrhosis has helped improve the treatment of ascites in these patients. It is likely that further unraveling of these pathophysiologic changes will lead to the development of novel and better treatment options. For example, the development of aquaretic agents for the management of hyponatremia in cirrhosis may allow more effective use of diuretic therapy. The ultimate challenge is to use the understanding of the pathophysiology to develop new strategies to prevent the development of ascites in cirrhosis.

Mechanisms of ascites formation

Ascites is the most common complication of cirrhosis. It is associated with profound changes in the splanchnic and systemic circulation and with renal abnormalities. The development of ascites is related to the existence of severe sinusoidal portal hypertension that causes marked splanchnic arterial vasodilation and a forward increase in the splanchnic production of lymph. Splanchnic arterial vasodilation also produces arterial vascular underfilling, arterial hypotension, compensatory activation of the RAAS, SNS, and AVP, and a continuous sodium and water retention, leading to ascites formation. Now, therefore, the splanchnic arterial circulation, rather than the venous portal system, is believed to be involved in the pathogenesis of ascites formation.

Effects of chronic octreotide treatment on renal changes during cirrhosis in rats

We examined the effect of a new long-acting release formula (LAR) of the somatostatin analogue, octreotide, on development of sodium retention and functional and structural changes in the thick ascending limb of Henle's loop (TAL) in rats with cirrhosis induced by common bile duct ligation (CBL). CBL and sham-operated control rats were treated with octreotide-LAR (10 mg/kg body weight subcutaneously, as a single dose) or vehicle at the time of CBL or sham-CBL. The rats were instrumented with chronic catheters, and sodium balance and renal function were examined 4 weeks after CBL or sham operation. Octreotide-LAR treatment significantly inhibited sodium retention in CBL rats and prevented renal vasodilatation without changes in glomerular filtration rate (GFR). The natriuretic response to a test dose of furosemide (7.5 mg/kg body weight intravenously) was significantly increased in CBL rats, and when expressed in terms of natriuretic efficiency (mmol Na/mg furosemide in urine), the natriuretic response was increased by 57% relative to sham-operated controls. Stereological examination of kidneys demonstrated a 53% increase in the volume of the inner stripe of the outer medulla and a 108% increase in the volume of TAL epithelium in cirrhotic rats relative to controls. The increased natriuretic efficiency of furosemide as well as the hypertrophy of the inner stripe and the TAL in this renal zone were absent in CBL rats treated with octreotide-LAR. These results suggest that octreotide-LAR treatment inhibits sodium retention in cirrhotic rats, partly by inhibition of increased furosemide-sensitive sodium reabsorption in the TAL.

The renal sympathetic and renin-angiotensin response to lower body negative pressure in well-compensated cirrhosis

BACKGROUND & AIMS

Certain antinatriuretic hormonal systems may be involved in the subclinical sodium handling abnormality in preascitic cirrhosis. The aims of this study were to determine the following in preascitic cirrhosis: (1) basal activity of the renal sympathetic and renin-angiotensin systems and (2) the relationship between the response of these systems to lower body negative pressure and sodium excretion.

METHODS

Seven preascitic cirrhotic patients and 9 age- and sex-matched controls were studied on a 150 mmol sodium per day diet. Systemic and renal hemodynamics, renal neurohormonal secretion rates, and sodium excretion were assessed before, during increasing levels of, and after lower body negative pressure, each for 30 minutes.

RESULTS

Both groups responded with a significant decrease in central venous pressure (P < 0.01) that remained higher in the cirrhotics than in the controls throughout the study. Cirrhotics showed significant increases compared with controls in renal renin and angiotensin II secretion rates at -20 mm Hg of lower body negative pressure, which was associated with significant renal sodium retention (96 +/- 17 micromol/min vs. 218 +/- 21 micromol/min at baseline, P < 0.05), but there was no change in renal sympathetic activity.

CONCLUSIONS

In preascitic cirrhosis, sodium retention occurs in response to lower body negative pressure, which was associated with increased renal renin-angiotensin activity. Stimulation of the intrarenal renin-angiotensin system may be the initial renal pathophysiological change causing sodium retention in cirrhosis.

Review: the controversy over the pathophysiology of ascites formation in cirrhosis

The pathogenesis of renal sodium retention and ascites formation in cirrhosis is a subject of much controversy. The generally accepted 'peripheral arterial vasodilatation hypothesis' seems to best explain the mechanism of sodium retention and other clinical findings, such as the hyperdynamic circulation of cirrhosis. However, recent data in pre-ascites and in early ascites do not seem to conform to the peripheral arterial vasodilatation hypothesis. Sodium handling abnormalities can be demonstrated in pre-ascitic cirrhosis when patients are challenged with a sodium load, in the absence of systemic vasodilatation or arterial underfilling. Therefore, an alternative hypothesis with a direct hepatorenal interaction, acting via sinusoidal portal hypertension and/or hepatic dysfunction as the affector mechanism, is proposed to be the initiating event in renal sodium retention in cirrhosis. The second and later process is the development of systemic arterial vasodilatation, possibly due to the presence of excess systemic vasodilators and/or decreased responsiveness of the vasculature to endogenous vasoconstrictors. This, in turn, will lead to a relatively underfilled circulation with consequent activation of neurohumoral systems, promoting further renal sodium retention as described by the peripheral arterial vasodilatation hypothesis and ultimately leading to ascites. When compensatory natriuretic mechanisms fail, refractory ascites develops and hepatorenal syndrome sets in. Thus, renal sodium retention in cirrhosis is the result of interplay of many factors, with direct hepatorenal interaction predominating in earlier stages of the cirrhotic process, while systemic vasodilatation becomes a more important pathogenetic factor as the disease progresses.

Pattern of sodium handling and its consequences in patients with preascitic cirrhosis

BACKGROUND/AIMS

The initial abnormalities in the renal sodium handling in patients with cirrhosis before developing ascites remain unknown. The aim of this study is to further characterize sodium metabolism and the effects of sodium loading in preascitic cirrhosis.

METHODS

Eight male, preascitic patients with cirrhosis and 6 volunteers had their daily urinary sodium excretion level measured while on a strictly metabolically controlled diet, first consisting of 20 mmol then of 200 mmol sodium per day each for 7 days. Central blood volume, plasma norepinephrine, and atrial natriuretic factor levels were measured during each diet.

RESULTS

Preascitic patients with cirrhosis had significantly less daily urinary sodium excretion on both diets. Volume expansion in the patients with cirrhosis was indicated by significantly greater weight gain and higher atrial natriuretic factor levels for each diet. Patients with cirrhosis had central blood volume expansion (1725 +/- 54 mL/m2) compared with controls (1495 +/- 81 mL/m2; P = 0.03) on a low-sodium diet. This increased significantly in the controls (1864 +/- 164 mL/m2; P = 0.04) on a high-sodium diet, associated with suppression of plasma norepinephrine, but not in the patients with cirrhosis (1679 +/- 107 mL/m2; P > 0.05).

CONCLUSIONS

Failure of further central blood volume expansion in the patients with cirrhosis on high-sodium diet in the presence of significant weight gain suggests maldistribution away from the effective arterial blood volume. This study provides further reasons why preascitic patients with cirrhosis might benefit from sodium restriction.