Written by: Dr. Jacquie Jacob, University of Kentucky

Ascites is a condition in which the abdominal cavity of chickens becomes full of fluid. For this reason it is often referred to as water belly.


The disease is most commonly caused by pulmonary hypertension resulting in the failure of the right ventricle, one of the heart’s four chambers. Ascites is most common in broilers raised at high altitudes (altitudes greater than 3,500 meters). The decreased supply of oxygen (hypoxia) at such altitudes can lead to pulmonary hypertension.

Ascites due to pulmonary hypertension can also occur in broilers raised in low-altitude areas. Ascites at low altitudes is usually the result of the demand for oxygen in fast-growing birds that have respiratory systems unable to handle such high demand. The oxygen requirement of fast-growing broilers can be reduced by slowing growth. Strategies to slow growth include reducing the number of hours of light exposure the birds experience per day or feeding birds a low-energy diet.

Ascites can also occur as a result of liver damage caused by aflatoxin or toxins from plants such as Crotalaria (also known as rattlebox or rattleweed) or by Clostridium perfringens infection. Amyloidosis is the most common cause of ascites in meat-type ducks and breeders. Amyloidosis is the accumulation of abnormal proteins (called amyloids) in one or more organ system.


Ascites syndrome in poultry. Merck Veterinary Manual.