Causes of Ascites
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Causes of Ascites

Why does fluid accumulate in the abdominal cavity?

Ascites, often referred to colloquially as “abdominal fluid” or “water in the abdomen,” is a pathological accumulation of fluid in the abdominal cavity. Normally, this space between the abdominal organs contains only a small amount of fluid, which acts as a lubricant so that the organs can move smoothly. However, when more fluid is produced than the body can eliminate, it accumulates—the abdomen enlarges and may cause discomfort. Ascites is not a disease in itself, but rather a sign that another underlying condition is present, which must be carefully investigated.

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Causes of Ascites

Why does fluid accumulate in the abdominal cavity?

Ascites, often referred to colloquially as “abdominal fluid” or “water in the abdomen,” is a pathological accumulation of fluid in the abdominal cavity. Normally, this space between the abdominal organs contains only a small amount of fluid, which acts as a lubricant so that the organs can move smoothly. However, when more fluid is produced than the body can eliminate, it accumulates—the abdomen enlarges and may cause discomfort. Ascites is not a disease in itself, but rather a sign that another underlying condition is present, which must be carefully investigated.

Overview

The development of ascites is a complex process influenced by various mechanisms in the body. Changes in blood circulation and fluid balance often play a role. For example, if pressure in certain blood vessels rises or the protein content in the blood drops, fluid can leak from the vessels into the abdominal cavity. Diseases that impair the function of the liver, kidneys, or heart can also lead to this accumulation of fluid.

There are basically two main types of ascites:

Low-protein fluid = transudative ascites

This form of ascites is common in liver diseases.

Protein-rich fluid = exudative ascites

This type of ascites is more commonly caused by inflammation or cancer.

Common Causes of Ascites

Here is a brief overview of common causes of ascites. These are explained in greater detail later on this page.

Liver cirrhosis

One of the most common causes is advanced liver damage, which is often triggered by alcohol abuse, viral infections (hepatitis), or other chronic liver diseases. In this process, liver tissue is gradually replaced by scar tissue, which leads to congestion in the inflowing vein—the portal vein—and causes increased pressure in the blood vessels. This promotes the leakage of fluid into the abdominal cavity.

Inflammation

There are also inflammatory causes, such as peritonitis or pancreatitis, which can cause irritation in the abdominal cavity and, as a result, fluid buildup.

Cancers

Cancer can cause ascites, particularly when tumor cells invade the peritoneum or block the lymphatic vessels, preventing fluid from draining properly.

Severe kidney disease

These can also play a role, since the kidneys are then no longer able to excrete excess fluid.

Heart Failure

Heart failure can cause fluid to build up in the body—not only in the legs, but also in the abdomen.

Procedure and Treatment

Since ascites is often a sign of a serious illness, a thorough medical examination is necessary. To determine the exact cause, a sample of the fluid is often taken from the abdomen and analyzed. Among other things, the protein content, cell count, and possible signs of infection or cancer cells are analyzed. Ultrasound or a computed tomography (CT) scan can also provide important clues about the underlying condition. Treatment is then tailored to the cause—often involving medication, a special diet, or, in some cases, drainage to remove the fluid and alleviate symptoms. Early diagnosis and targeted therapy are crucial for preventing serious complications and improving quality of life.

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Procedure and Treatment

Since ascites is often a sign of a serious illness, a thorough medical examination is necessary. To determine the exact cause, a sample of the fluid is often taken from the abdomen and analyzed. Among other things, the protein content, cell count, and possible signs of infection or cancer cells are analyzed. Ultrasound or a computed tomography (CT) scan can also provide important clues about the underlying condition. Treatment is then tailored to the cause—often involving medication, a special diet, or, in some cases, drainage to remove the fluid and alleviate symptoms. Early diagnosis and targeted therapy are crucial for preventing serious complications and improving quality of life.

Liver cirrhosis

The most common cause of ascites is advanced liver cirrhosis —a serious disease in which healthy liver tissue is gradually replaced by scar tissue. As a result, the liver loses its normal function, which has serious consequences for the entire body. One of the liver’s most important functions is to filter and process blood from the digestive tract. However, when the tissue is scarred, blood can no longer flow freely through the liver but instead backs up into the portal vein —a large blood vessel that carries nutrient-rich blood from the intestines to the liver. This increased pressure in the portal vein (portal hypertension) causes fluid to leak from the blood vessels into the abdominal cavity.

In addition, liver cirrhosis has another significant effect: it reduces the production of albumin, an important protein that normally helps keep fluid within the blood vessels. Low albumin levels in the blood (hypoalbuminemia) cause even more fluid to leak from the blood vessels into the surrounding tissue and the abdominal cavity, contributing to the development of ascites.

Because the liver plays a central role in metabolism, cirrhosis can also lead to other symptoms, such as jaundice (yellowing of the skin and eyes), increased fatigue, or a heightened susceptibility to infections. In many cases, the disease progresses over the course of years, often unnoticed, until the first symptoms appear—including ascites.

Early treatment of liver cirrhosis can help slow the progression of the disease and reduce the risk of ascites. This includes consistent treatment of the underlying cause, such as abstaining from alcohol in cases of alcohol-related liver cirrhosis or taking antiviral medications for a hepatitis infection. If ascites is already severe, diuretics or targeted drainage of the fluid (paracentesis or a permanent catheter) can help alleviate symptoms.

Accompanying symptoms of ascites caused by liver cirrhosis:

Yellowing of the skin (jaundice)

Weight Loss and Muscle Wasting

Enlarged veins on the abdominal wall (Caput medusae)

Fatigue and difficulty concentrating

Malignant Ascites

Fluid Accumulation Due to Tumors

Not only liver diseases but also cancers can lead to the development of ascites. When the fluid buildup is caused by cancer, it is referred to as malignant ascites. It occurs particularly frequently in cases of colorectal cancer, stomach cancer, ovarian cancer, or pancreatic cancer. In these cases, the cancer cells spread to the peritoneum, a thin layer of tissue that lines the abdominal cavity and surrounds the organs.

One of the main causes of malignant ascites is obstruction of the lymphatic vessels. Normally, the lymphatic vessels help remove excess fluid from the abdominal cavity. However, if these vessels are obstructed or damaged by tumors, the fluid can no longer drain and instead accumulates in the abdominal cavity. Another mechanism involves changes in the permeability of blood vessels: Certain tumor cells can release signaling molecules that make the vessel walls more permeable

so that fluid can escape more easily. Patients often notice a sudden increase in abdominal girth, accompanied by a feeling of pressure, digestive problems, and often pain as well. Since the underlying tumor is usually at an advanced stage, treatment in many cases focuses on alleviating symptoms.

To reduce fluid buildup, targeted fluid drainage (paracentesis), indwelling catheter systems, or special medications that slow cell growth can be used. In some cases, chemotherapy can also help control tumor growth and thereby reduce fluid accumulation. Since malignant ascites is often accompanied by general physical weakness, comprehensive palliative care is important to maintain the quality of life of those affected as much as possible.

Signs of malignant ascites:

Rapid recurrence after a puncture

Increasing Waist Circumference Despite Weight Loss

Pain and Digestive Problems

General weakness and loss of appetite

Heart Failure

When the heart can no longer pump effectively

In addition to liver disease and cancer , heart failure can also lead to the development of ascites. The heart is responsible for pumping blood throughout the body, thereby supplying all organs with oxygen and nutrients. However, if the heart is weakened and can no longer function at full capacity, blood can back up in the veins—especially in the large blood vessels that carry blood from the body back to the heart.

This backflow in the veins that carry blood to the heart causes fluid to leak from the blood vessels into the surrounding tissue. Initially, the legs and ankles are often swollen (edema); later, fluid may also accumulate in the abdominal cavity, resulting in ascites. This form of fluid accumulation occurs particularly frequently in advanced heart failure, when the heart is no longer able to effectively pump oxygen-poor blood from the body to the lungs.

Typical symptoms associated with cardiac ascites include swelling in the legs, a growing feeling of pressure in the abdomen, and shortness of breath (dyspnea). The latter can become particularly severe when lying down, as the fluid then presses more strongly on the diaphragm, leaving less room for the lungs to expand. Affected patients often feel weak, tire easily, and gain weight, although this weight gain is not due to fat but to retained fluid.

Treatment depends primarily on the cause of heart failure. Medications such as diuretics (water pills) can help remove excess fluid from the body and relieve symptoms. A low-sodium diet can also help reduce fluid retention in the body. In more severe cases, it may be necessary to relieve ascites through targeted drainage. Since heart failure is a chronic condition, long-term treatment with heart medications, exercise therapy, and, if necessary, management of heart function through a pacemaker or other procedures is required to stabilize the course of the disease.

Typical symptoms of ascites caused by heart failure.

Shortness of breath, especially when lying down

Declining physical stamina

Fluid retention in the legs (leg edema)

Weight Gain Due to Water Retention

Conclusion

Ascites as a Warning Sign of Serious Illnesses

In most cases, ascites is a sign of a serious illness, particularly of the liver, heart, or abdominal cavity. A thorough medical evaluation is crucial to identify the cause and initiate the best possible treatment. Treatment depends on the underlying condition and may involve medication, drainage, or, in severe cases, surgery.

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Conclusion

Ascites as a Warning Sign of Serious Illnesses

In most cases, ascites is a sign of a serious illness, particularly of the liver, heart, or abdominal cavity. A thorough medical evaluation is crucial to identify the cause and initiate the best possible treatment. Treatment depends on the underlying condition and may involve medication, drainage, or, in severe cases, surgery.

Do you have any questions?

Contact us now or browse a selection of frequently asked questions from patients here.

... Contact us now!... What questions do patients or their family members ask?