What is ascites?

Ascites is a buildup of fluid in the abdomen. When it’s severe, ascites can cause stomach swelling (distention), abdominal pain, and difficulty breathing, nausea and vomiting and difficulty eating. 

There are several kinds of ascites. Two common forms are caused by liver cirrhosis (liver disease), or certain cancers of the abdomen. When the buildup of fluid contains chyle (a milky fluid that’s a combination of lymphatic fluid and fat), this form of ascites is known as chylous ascites and is a lymphatic flow disorder. 

The lymphatic system plays a crucial role in immune function and in the delivery of vital nutrients to the body. Functioning almost like a sponge, the lymphatic system absorbs excess lymph fluid — watery fluid containing protein, electrolytes, cells and other substances — from the body’s organs and returns it to the blood stream. Injury to lymphatic vessels, congenital abnormalities or excessively high venous pressures can result in lymphatic flow problems and leakage of lymphatic fluid into the peritoneum leading to ascites. 

In a healthy body, the lymphatic channels from the liver and mesentery drain toward the thoracic duct, which is the main lymphatic vessel responsible for lymph drainage. In children and adults with ascites, however, channels originating in the intestine or in the liver begin to flow in the opposite direction, creating leaks in the peritoneum. As lymphatic fluid spills in to the peritoneum, there is no way for the body to absorb it. 

What causes ascites? 

Ascites can have many potential causes, including:

• Injuries to the central lymphatic system due to surgery or trauma (this is also known as traumatic chylous ascites)
• Congenital lymphatic malformations such as lymphangiomatosis
• Tumors
• Systemic diseases or infections such as tuberculosis
• Congenital syndromes such as Gorham-Stout, Noonan and Turner syndromes
• Elevated venous pressures due to heart failure, pulmonary hypertension or congenital heart surgery

Signs and symptoms of ascites

Initially, ascites causes few symptoms. When enough fluid accumulates, though, affected individuals will have either painless abdominal swelling or stomach pain.

Sometimes, fluid from the abdomen can travel through openings in the diaphragm and lead to accumulation of fluid in the chest. When this happens, it can cause breathing difficulties.

Diagnosis of ascites

Doctors use a combination of imaging tests to diagnose ascites. Tests may include X-ray, CT, ultrasound or MRI. A diagnosis of ascites is made when these tests demonstrate the presence of fluid in the peritoneal spaces.

Your doctor may also use a thin needle to withdraw some of the accumulated fluid. The fluid can then be tested to determine whether it originated in the lymphatic system.

Additionally, lymphatic imaging techniques, such as intranodal lymphangiography and dynamic contrast magnetic resonance lymphangiography, might be used to determine the exact source of the fluid.