What Is Ascites? Definition
The organs of the abdomen are contained in a sac or membrane called the peritoneum. Normally the peritoneal cavity contains only a small amount of fluid, although in women this can vary (by 20ml, or less than an ounce) depending on the menstrual cycle. "Ascites is the term used to denote increased fluid in the peritoneal cavity, a situation that is not normal.
There are a variety of diseases that can cause the fluid to accumulate and the reasons that the ascites occurs may be different for each disease. Cancer that spreads to the peritoneum can cause direct leakage of fluid, while other illnesses cause an excess accumulation of water and sodium in the body. This fluid can eventually leak into the peritoneal cavity.
Most commonly, ascites is due to liver disease and the inability of that organ to produce enough protein to retain fluid in the bloodstream as well as obstruction to flow through the scarred cirrhotic liver. Normally, water is held in the bloodstream by oncotic pressure. The pull of proteins keeps water molecules from leaking out of the capillary blood vessels into surrounding tissues. As liver disease advances, the liver’s ability to manufacture proteins is decreased, so oncotic pressure decreases because of lack of total protein in the body, and water leaks into surrounding tissues.
In addition to ascites, the extra fluid can be appreciated in many other areas of the body as edema (swelling). Edema can occur in the feet, legs, chest cavity, a variety of other organs, and fluid can accumulate in the lungs. Symptoms caused by this excess fluid will depend upon its location.
Causes of Ascites
The list of causes of ascites begins with the liver. Regardless of the reason for liver failure, a malfunctioning liver cannot make enough protein to maintain oncotic pressure to keep fluid in the circulatory system.
Causes of ascites due to liver problems include:
- Cirrhosis describes a form of liver disease in which liver tissue that is damaged is replaced by scar tissue. As more liver tissue is lost, progressive liver failure occurs. Alcoholic liver disease or alcoholic hepatitis (hepar=liver +itis=inflammation), viral hepatitis (B or C), and fatty liver disease are the most common causes for cirrhosis.
- Acute liver failure can result in ascites. This may be due to any acute injury to liver cells including adverse reactions to medications or drug abuse (for example, liver failure is the major consequence of acetaminophen overdose).
- Budd-Chiari syndrome is caused by the blockage of the hepatic veins (those that drain the liver). This causes the triad of ascites, abdominal pain, and hepatosplenomegaly (enlargement of the liver and spleen).
- Cancer that has metastasized or spread to the liver can also be the source of ascites.
Other causes of ascites include:
- Heart failure is the inability of the heart muscle to adequately pump the fluid within the blood vessels. This can cause a variety of problems, but most notably, fluid backs up into the lungs and other organs causing them to fail. This water overload can cause leakage into the peritoneal cavity and the formation of ascites.
- Nephrotic syndrome, in which kidney damage causes protein to leak into the urine, decreases oncotic pressure and may result in ascites.
- Disorders of the pancreas can result in ascites in a variety of ways. Acute pancreatitis (inflammation of the pancreas) can cause fluid accumulation as part of the inflammatory response. Chronic pancreatitis can result in malnutrition, leading to decreased total body protein, loss of oncotic pressure, and ascites. Pancreatic cancer can cause direct fluid loss.
- Direct irritation of the peritoneum can cause it to leak fluid as part of the inflammation process. This irritation may be due to amalignancy (cancer) or infection.
- Diseases of the ovary can be associated with ascites. Cancer of the ovary has no initial symptoms, and many women will have the diagnosis made because they develop ascites. Meigs syndrome is a benign tumor of the ovary called a fibroma that presents with ascites and pleural effusion (fluid in the cavities surrounding the lungs). The hard surface of anovarian tumor may cause significant irritation of the peritoneum, causing it to leak fluid.
- Ascites is found uncommonly inhypothyroidism (low thyroid function). Usually the hypothyroidism has been untreated for a prolonged period of time, and the ascites resolves when thyroid levels in the body return to normal.
There is a distinction between patients who develop ascites because of liver disease and cirrhosis, and those who develop it because of inflammation of the peritoneum because of cancer. Liver disease tends to be relatively painless, while cancer patients experience significant amounts of pain.
Otherwise, the symptoms are similar. There is swelling of the abdomen to accommodate the fluid buildup. This may make it difficult for the diaphragm (the flat muscle that separates the chest form the abdomen) to assist with breathing, causing shortness of breath.
While a tense abdomen filled with fluid is easy to recognize, initially, the amount of ascites fluid may be small and difficult to detect. As the amount of fluid increases, the patient may complain of a fullness or heaviness in the abdomen. It is often the signs of the underlying disease that initially brings the patient to seek medical care.
In cirrhosis of the liver, not only does fluid accumulate in the abdominal cavity, but there may be leg swelling,easy bruising, enlargement of the breasts, and confusion due to encephalopathy (encephalo=brain + pathy=disorder).
If the ascites is due to heart failure, there may be shortness of breath as well as leg swelling (edema). The shortness of breath tends to be worse with activity and with lying flat (orthopnea). Patients with ascites due to heart failure tend to waken in the middle of the night, with paroxysmal nocturnal dyspnea (dys= abnormal + pnea= breathing).
When to Seek Medical Care for Ascites
In general, unexplained abdominal swelling for any cause is a reason to seek medical care.
For those who have known ascites, fever and abdominal pain should be a warning that the fluid may be infected and care should be accessed immediately.
Exams and Tests for Ascites
Sometimes it is difficult for a health care practitioner to appreciate that ascites is present. Most commonly, however, the patient presents with the complaint of abdominal fullness and pressure, and the ascites can be found on physical examination. The diagnosis is aided by learning the past medical history of the patient so the physician can make the decision to order additional tests.
A complete blood count (CBC) may be helpful in looking for potential infection (an elevated white blood cell count), anemia (a low hemoglobin), and indirectly, liver function (low platelet count). Other blood tests are helpful in assessing electrolyte balance, kidney and liver function, and the amount of protein in the body.
If a patient presents with new-onset ascites, paracentesis is recommended to obtain samples of the fluid for analysis to assist in making the diagnosis. Removal of the fluid may assist with symptom control (see below). Paracentesis is a sterile procedure whereby a needle is placed through the abdominal wall into the peritoneal cavity and fluid is removed.
Gastroenterologists (specialists in the digestive system including the liver) use a formula measuring the amount of albumin (protein) in the blood compared to the amount found in the ascites fluid to help them classify the type of ascites and assist with the diagnosis. If the amount of protein is higher in the ascites than in the serum, it may be due to liver disease, heart failure, Budd-Chiari, pancreatitis, ovarian cancer, or malnutrition. If the ascites protein is lower, then certain infections and malignancies are more likely.
Laboratory tests on the ascites fluid may include evaluation for infection and the assessment of electrolytes and other substances.
Ascites Self-Care at Home
For patients with liver disease as the cause of cirrhosis, abstention from alcohol is an important first step in treatment to minimize further liver damage. Acetaminophen-containing medications should also be minimized since they require metabolism in the liver.
Medical Treatment for Ascites
Excess fluid in the abdominal cavity can cause significant discomfort and shortness of breath. The method of treatment depends upon the reason for the ascites accumulation, how quickly the fluid has accumulated, whether it is a first occurrence or a repeated event, and how significantly the symptoms affect the patient.
Lifestyle Changes and Medication
For patients with cirrhosis, the initial therapy for ascites begins with dietary salt restriction and medications to assist the body in ridding itself of excess salt and fluid. Spironolactone (Aldactone) is a first line diuretic medication that helps block the chemical aldosterone which is responsible for salt retention in the body. Furosemide (Lasix) and metolazone (Zaroxolyn) may also be added. This treatment is effective in controlling ascites fluid in the vast majority of patients.
Body weight is used as a measurement of ascites control. The goal for diuretic therapy is to lose between one to two pounds of weight per day depending upon underlying medical conditions. Once most of the ascites fluid is gone, medication dosing will be individualized to the patient's needs.
Water restriction may be considered if hyponatremia, (low serum sodium) is present.
Paracentesis: If diuretics and diet fail, paracentesis may be the next step in the treatment offered. Under sterile conditions, a needle is placed into the peritoneal space and fluid is withdrawn. Paracentesis may be considered as a first step if the ascites fluid accumulates quickly and the abdominal distension causes pain or shortness of breath. Because the peritoneal fluid contains albumin, if large amounts of fluid (more than 5 liters) are withdrawn, an albumin transfusion may be needed.
Paracentesis may be done more than once, but if it becomes a frequent necessity for symptom control, other options may be considered.
The complications of paracentesis include infection, bleeding, electrolyte disturbances, and perforating an organ such as the intestine. However, in tense ascites, the benefits outweigh the risks in providing relief to the patient.
- Transjugular intrahepatic portosystemic shunt (TIPS): TIPS diverts fluid from the portal vein into the central blood circulation, thus decreasing pressure in the liver and decreasing ascites formation. An interventional radiologist is able to thread a catheter or stent underneath the skin from the internal jugular vein to the hepatic vein while the patient is sedated.
- Liver transplant: Patients who have cirrhosis and ascites should be considered as candidates for potential liver transplantation.
- Cancer: In patients with ascites from cancer, diet restrictions and diuretics are not effective. Paracentesis may be the first-line treatment. If needed, the catheter maybe left in place to drain, so that fluid can be removed as needed and the patient does not need to undergo repeated procedures.
- Peritoneovenous shunting: Peritoneovenous shunting is a surgical operation that may increase short-term survival in cancer patients who are not candidates for, or who have failed treatment with, paracentesis. Shunting may be also considered for patients who have refractory ascites and are not candidates for paracentesis, liver transplant, or a TIPS procedure.
Follow-up for Diuretic Therapy
Body weight is used as a measurement of ascites control. The goal for diuretic therapy is to lose between one to two pounds of weight per day depending upon the underlying medical conditions. Once most of the ascites fluid is gone, medication dosing will be individualized to the patient's needs.
Though there are many causes of ascites, the most preventable cause is alcohol abuse. Patients who drink alcohol to excess are at risk for developing liver failure and subsequent ascites.
Ascites Outlook (Prognosis)
Alcohol abuse is the most easily treated cause of ascites and has the best outcome. Still, for those patients who develop ascites from cirrhosis, half will die within three years. If refractory ascites occurs, the mortality rate at one year is 50%.
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care
Runyon, BA. "AASLD Practice Guidelines. Management of Adult Patients with Ascites Due to Cirrhosis: An Update." Hepatology, Vol. 49, No. 6, 2009