(See also Overview of Liver Disease.)
The most common cause of ascites is
Less common causes of ascites include disorders unrelated to the liver, such as cancer, heart failure, kidney failure, inflammation of the pancreas (pancreatitis), and tuberculosis affecting the lining of the abdomen.
Ascites tends to occur in long-standing (chronic) rather than in short-lived (acute) liver disorders. It most commonly results from
Portal hypertension—high blood pressure in the portal vein (the large vein that brings blood from the intestine to the liver) and its branches
Ascites may occur in other liver disorders, such as severe alcoholic hepatitis without cirrhosis, chronic hepatitis, and obstruction of the hepatic vein (Budd-Chiari syndrome).
In people with a liver disorder, ascitic fluid leaks from the surface of the liver and intestine and accumulates within the abdomen. A combination of factors is responsible. They include the following:
Also, albumin usually leaks from blood vessels into the abdomen. Normally, albumin, the main protein in blood, helps keep fluid from leaking out of blood vessels. When albumin leaks out of blood vessels, fluid also leaks out.
Small amounts of fluid within the abdomen usually cause no symptoms. Moderate amounts may increase the person's waist size and cause weight gain. Massive amounts may cause abdominal swelling (distention) and discomfort. The abdomen feels taut, and the navel is flat or even pushed out.
The swollen abdomen puts pressure on the stomach, sometimes leading to loss of appetite, and pressure on the lungs, sometimes leading to shortness of breath.
In some people with ascites, the ankles swell because excess fluid accumulates there (causing edema).
Spontaneous bacterial peritonitis (infection of the ascitic fluid that develops for no apparent reason) sometimes occurs. This infection is common among people with ascites and cirrhosis, especially alcoholics.
If spontaneous bacterial peritonitis develops, people usually have abdominal discomfort, and the abdomen may feel tender. People may have a fever and feel generally unwell. They may become confused, disoriented, and drowsy. Untreated, this infection can be fatal. Survival depends on early treatment with appropriate antibiotics.
When a doctor taps (percusses) the abdomen, the fluid makes a dull sound. If the person's abdomen is swollen because the intestines are distended with gas, the tapping makes a hollow sound. However, a doctor may not be able to detect ascitic fluid unless the volume is about a quart or more.
If doctors are uncertain whether ascites is present or what is causing it, they may do ultrasonography or computed tomography (CT; see Imaging Tests of the Liver and Gallbladder). In addition, a small sample of ascitic fluid can be withdrawn by inserting a needle through the wall of the abdomen—a procedure called diagnostic paracentesis. Laboratory analysis of the fluid can help determine the cause.
The basic treatment for ascites is a low-sodium diet with a goal of 2,000 mg or less of sodium per day.
If diet is ineffective, people are usually also given drugs called diuretics (such as spironolactone or furosemide). Diuretics make the kidneys excrete more sodium and water into the urine so people urinate more.
If ascites becomes uncomfortable or makes breathing or eating difficult, the fluid may be removed through a needle inserted into the abdomen—a procedure called therapeutic paracentesis. The fluid tends to reaccumulate unless people also follow a low-sodium diet and take a diuretic. Because a large amount of albumin is usually lost from the blood into the abdominal fluid, albumin may be given intravenously.
If large amounts of fluid accumulate frequently or if other treatments are ineffective, a portosystemic shunt or liver transplantation may be needed. The portosystemic shunt connects the portal vein or one of its branches with a vein in the general circulation and thus bypasses the liver. However, placement of the shunt is an invasive procedure and can cause problems, such as deterioration of brain function (hepatic encephalopathy) and deterioration of liver function.
If spontaneous bacterial peritonitis is diagnosed, people are given antibiotics such as cefotaxime. Because this infection often recurs within a year, a different antibiotic (such as norfloxacin) is given after the initial infection resolves to prevent the infection from recurring.