Hepatorenal syndrome (HRS) is a form of impaired kidney function that occurs in individuals with advanced liver disease. Individuals with hepatorenal syndrome do not have any identifiable cause of kidney dysfunction and the kidneys themselves are not structural damaged. Therefore, hepatorenal syndrome may be referred as a "functional" form of kidney impairment. In fact, if the kidney of an individual with hepatorenal syndrome were to be transplanted into an otherwise healthy individual, it would function normally. Hepatorenal syndrome is classified into to two distinct types. Type I is a rapidly progressive condition that leads to renal failure; type II does not have a rapid course and progresses slowly over weeks to months.

Although the hepatorenal syndrome occurs in individuals with liver disease, the exact cause of the condition is unknown. Researchers have noted that blood circulation is abnormal in individuals with hepatorenal syndrome. The arteries that circulate oxygenated blood from the lungs to the rest of the body (systemic circulation) widen in contrast to the arteries of the kidney, which narrow causing a decrease in the blood flow through the kidney. Many affected individuals also have high blood pressure of the branches of the portal vein (portal hypertension), the main vein that carries blood from the intestines to the liver.

Individuals with hepatorenal syndrome will have a variety of nonspecific symptoms including fatigue, abdominal pain, and a general feeling of ill health (malaise). Affected individuals also have symptoms related to advanced liver disease including the accumulation of fluid in the abdomen (ascites), yellowing of the skin and the whites of the eyes (jaundice), an enlarged spleen (splenomegaly) and an enlarged, extremely tender liver (hepatomegaly).

Hepatorenal syndrome type I is characterized by a rapid decrease in kidney function. The kidneys act as a filtration system removing unwanted substances and excess fluid from the body. Symptoms of decreasing renal function include the accumulation of excess watery fluid in the spaces between the tissues and organs causing swelling of these areas (edema), dramatically decreased urination, and the presence of increased nitrogenous waste products such as creatinine and BUN in the blood (azotemia). Hepatorenal syndrome type I can progress to life-threatening renal failure within days.

Individuals with hepatorenal syndrome type I are more likely to suffer from hepatic encephalopathy, a condition that occurs when the liver fails to breakdown (metabolize) certain substances in the body. These substances travel through the bloodstream to the brain with toxic effects. Hepatic encephalopathy may cause confusion, drowsiness, recognizable changes in judgment and other intellectual processes, and other psychological alterations. It also is more likely to occur with acute liver failure due to any cause.

Hepatorenal syndrome type II causes renal dysfunction that generally progresses much slower than it does in type I. Affected individuals are less likely to develop jaundice and usually do not develop hepatic encephalopathy. Individuals with hepatorenal syndrome type II often develop accumulation of fluid in the abdomen (ascites) does not respond to treatment with diuretics, which are drugs that help remove excess fluid from the body. This finding is referred to as diuretic-resistant ascites. It can occur over weeks to months with a slow rise of BUN and Creatinine.

The exact cause of hepatorenal syndrome is unknown. It occurs in individuals with advanced liver disease, especially individuals who have scarring and dysfunction of the liver (cirrhosis). The characteristic finding in individuals with hepatorenal syndrome is narrowing (constriction) of the blood vessels that feed the kidneys (renal vasoconstriction), which results in decreased blood flow to the kidneys, eventually impairing kidney function.

The reason that renal vasoconstriction occurs is unknown. Researchers believe that the complex interaction of several different factors is involved including high blood pressure of the main blood vessels of the liver (portal hypertension), abnormalities in the physical factors that govern blood flow (systemic hemodynamics), the activation of substances that cause blood vessels to narrow (vasoconstrictors) and suppression of substances that cause blood vessels to widen (vasodilators).

Researchers have also determined that cirrhotic cardiomyopathy may also contribute to the development of hepatorenal syndrome in some individuals. Cirrhotic cardiomyopathy refers to the abnormal functioning of the heart in individuals with scarring of the liver (cirrhosis). Cirrhotic cardiomyopathy results in decreased cardiac outflow (heart failure) and abnormal widening of certain arteries in the body.

In some individuals with hepatorenal syndrome, certain ‘triggers’ can be identified that make it more likely for individuals with liver disease to developed impaired kidney function (hepatorenal syndrome). There triggers are called precipitating factors. The most common precipitating factor is spontaneous bacterial peritonitis (SBP), an infection of the thin membrane (peritoneum) that lines the abdominal cavity. SBP is a known complication in individuals with ascites and cirrhosis. Other common triggers are acute blood loss from the gastrointestinal tract (GI bleeding), low blood pressure and infection from any cause.

The only curative therapy for individuals with hepatorenal syndrome is a liver transplant, which corrects both the liver disease and associated impaired renal function. Even after successful liver transplantation, patients who had hepatorenal syndrome beforehand may not fully recover their kidney function. A small percentage may go on to permanent damage requiring dialysis. Much research is ongoing to determine which patients will recover and which may not. Those who may not recover may need a kidney transplant with their liver transplant. However, due to a limited amount of donors and long waiting lists, a liver transplant is not always feasible. For patients who develop hepatorenal syndrome with acute liver failure and not cirrhosis, recovery from hepatorenal syndrome can occur if the liver recovers. However, individuals with hepatorenal syndrome requiring dialysis or suffering from advanced kidney failure for 6-8 weeks before receiving a liver transplant, may require a kidney transplant with their liver transplant, as kidney function may not recover.

Individuals with liver disease and the hepatorenal syndrome who receive a liver transplant have a lower success rate than in individuals with liver disease and normal kidney function who receive a liver transplant. Therefore, many of the therapies used to treat hepatorenal syndrome are done to improve kidney function in individuals eligible for a liver transplant.

For individuals awaiting a transplant, several therapies to maintain kidney function may be used. Paracentesis is a surgical procedure that removes the excess fluid from the abdomen (ascites). Under carefully controlled conditions, this procedure may benefit some affected individuals. In addition, avoiding diuretics (which can worsen kidney function), maintaining electrolyte balance, and promptly treating infection may also be necessary.

HRS is always a complication of liver disease. The condition is almost always caused by cirrhosis of the liver. If you have cirrhosis, certain factors increase your risk of HRS. These include:

• unstable blood pressure
• use of diuretics
• acute alcoholic hepatitis
• gastrointestinal bleeding
• spontaneous bacterial peritonitis
• other infections (especially in the kidneys)

Currently, the only curative therapy for patients with hepatorenal syndrome is a liver transplant, which treats both liver diseases and associated impaired renal functions. However, even after the liver transplantation, the treated patients have lower chances of recovering from their kidney disease.

• Liver Transplantation – It is one of the best treatments for HRS, but it's not an optimal option for people with HRS-1, who are too sick to undergo the procedure.
• Renal Replacement Therapy – People who are not eligible for a transplant or waiting for a donor will be given hemodialysis to enhance the blood flow to the kidneys.
• Dialysis – Even after a successful liver transplant, dialysis will be required to control the persistent kidney problems.
• Medications - A class of drugs called systemic vasoconstrictors, including terlipressin, ornipressin, and octreotide, is prescribed to treat the symptoms of hepatorenal syndrome. For instance, terlipressin is shown improved renal function in affected [patients.
• Besides the above-mentioned options, there are various new treatments that are being studied, including transjugular intrahepatic portosystemic shunt and more, to cure the condition.