In medicine (gastroenterology), ascites (also known as peritoneal cavity fluid, peritoneal fluid excess, hydro peritoneum or more archaically as abdominal dropsy) is an accumulation of fluid in the peritoneal cavity. Although most commonly due to cirrhosis and severe liver disease, its presence can portend other significant medical problems. Diagnosis of the cause is usually with blood tests, an ultrasound scan of the abdomen, and direct removal of the fluid by needle or paracentesis (which may also be therapeutic).

A person with ascites usually has severe liver disease. Ascites due to liver disease is caused by high pressure in the blood vessels of the liver (portal hypertension) and low albumin levels.
Disorders that may be associated with ascites include:

• Cirrhosis and any illness that leads to it
• Clots in the veins of the liver (portal vein thrombosis)
• Colon cancer
• Congestive heart failure
• Constrictive pericarditis
• Hepatitis
• Infections such as tuberculosis
• Liver cancer
• Nephrotic syndrome
• Ovarian cancer, endometrial cancer
• Pancreatitis
• Pancreatic cancer
• Protein-losing enteropathy
• Treatment may be with medication (diuretics), paracentesis, or other treatments directed at the cause