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Hepatorenal Syndrome (HRS) Articles Referenced:
Summary: Definition: Occurs in advanced liver disease and portal hypertension in the setting of cirrhosis usually, but can occur with alcoholic hepatitis or in acute liver failure. A combination of circulatory and kidney dysfunction. The principal abnormality of circulation is low arterial pressure due to greatly reduced total systemic vascular resistance. Kidney function is impaired due to a severe reduction in renal blood flow. Pathogenesis: Hallmark is vasoconstriction of the renal circulation, the precise reason is not definite. There is severe arterial under filling in the systemic circulation due to pronounced vasodilation of the splanchnic circulation due to portal hypertension, suspected to result from nitric oxide production which causes vasodilation. The theory is that the arterial vasodilation activates the RAS, sympathetic system, and arginine vasopressin, leading to renal vasoconstriction as a homeostatic response to correct the problem. Renal function and GFR are reduced. Tubular remains normal. These response cause retention of sodium (RAS, sympathetic) and water (vasopressin). In the early phases, the kidneys produce prostaglandins that act as vasodilators and help prevent problems. Eventually, this becomes overwhelmed by the vasoconstrictor effects related to the low SVR. Incidence: Can occur in the late stages of advanced cirrhosis commonly. Ascites is often present. Up to 40% will develop it over 5 years in severe cirrhosis and ascites. Clinical & Lab Findings: Patients with ascites, with renal sodium retention and dilutional hyponatremia are at high risk for HRS. The dominant finding of HRS is renal failure. Other manifestations include: electrolyte, cardiovascular, infectious, and liver related complications. It is commonly diagnosed by the finding of an increasing concentration of BUN and creatinine. Progressive oligoanuria generally develops. This process may be rapid or slow. These processes define two different patterns of progression. Type 1 HRS is defined as a 100% increase in serum creatinine to >2.5 mg/dL in less than two weeks. In Type 1 HRS, the creatinine generally increases rapidly to very high levels. The short term outlook with Type 1 HRS is poor. Type 2 HRS is marked by an increase in creatinine that is slower than Type 1. Some people with Type 2 disease may eventually convert to Type 1 disease. The most common feature of Type 1 disease is severe renal failure, whereas, for Type 2 disease the most common finding is ascites. In general, patients with HRS have sodium retention with salt and water overload. This will have generally preceded the development of HRS. There will be weight gain, ascites, edema, and hyponatremia. Hyponatremia is nearly universal such that it's absence would cause one to question the diagnosis or suggest a need to look for other associated causes of renal failure. The hyponatremia results from impaired capacity to excrete solute free water, which results in a disproportionate retention of water compared to sodium that is being retained. The result is dilutional hyponatremia. This primarily results from arginine vasopressin release related to arterial under filling. It exists before HRS, but worsens as HRS develops. Hyperkalemia may develop, usually gradually. Monitor for and treat hyperkalemia aggressively if it develops. Cardiovascular function is effected with notable low SVR, low arterial pressure, activation of major vasoconstrictor systems, an often increased cardiac output (but sometimes reduced). Mean arterial pressure is ~70 mm Hg. Suspect infection when hemodynamic instability develops. Pulmonary edema is rare in HRS, except when volume expanders are used aggressively. Common infectious complications of HRS include: sepsis (spontaneous or due to indwelling catheters), spontaneous bacterial peritonitis (SBP), and pneumonia. Obviously, acute renal failure and chronic liver disease predispose to infectious complications also. Patients will likely have the sequelae of chronic liver disease including: jaundice, coagulopathy, malnutrition, and hepatic encephalopathy. Ascites will always be present in HRS. When ascites is absent you should consider other causes for acute renal failure such as volume depletion or excessive diuresis. Precipitating Factors: May be spontaneous. May be due to factors causing circulatory compromise with renal hypoperfusion. Consider bacterial infections, large volume paracentesis, and GI bleeding. Only SBP is known to cause HRS. About 20% with SBP will develop Type 1 HRS. Up to 15% of people with large volume paracentesis (over 5 liters of peritoneal fluid ) will develop HRS if volume expanders are not given. Some believe diuresis can precipitate HRS, but evidence is lacking. Prognosis: Survival rates are very low and spontaneous recovery is very rare. For Type 1 disease hospital survival is <10%. With Type 2 disease median survival is 6 months. Survival is worse with more advanced Child-Pugh class. Diagnostic Workup: Estimate the GFR. Measure creatinine clearance off diuretics. Diagnosis is by exclusion as there is no specific test. You must rule out ARF due to prerenal conditions, nephrotoxic drugs, acute tubular necrosis (ATN) from shock, infection related ARF, proteinuria or hematuria from parenchymal kidney disease. This can generally be accomplished with history, blood and urine tests, and renal ultrasound. In HRS urine sodium is usually <10 mmol/L due to preserved renal tubular function. However, in ATN the urine sodium is generally >10 mmol/L. However, urine sodium may be low in cirrhosis with ATN and may not be low in HRS. Therefore, history is very important in distinguishing ATN from HRS. ATN should be considered when ARF develops in the presence of hypovolemia, septic shock or nephrotoxic agents. Management of Type 1 HRS:
Management of Type 2 HRS:
Prevention: In the case of spontaneous bacterial peritonitis the administration of albumin with antibiotics has been shown to reduce the rate of HRS from 33% in the control group to 10% in those treated with both. Hospital mortality went from 29% down to 10%. In patients with alcoholic hepatitis, the use of pentoxifylline 400 mg TID with food, results in a decrease in occurrence of 8% and mortality of 24% compared to a control group at 35% and 46% respectively. These studies need further confirmation.
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