Written by: Dr. Jacquie Jacob, University of Kentucky
The reproductive tract of a hen is made up of two parts: the ovary and the oviduct (see the article "Avian Reproductive System—Female" for more information about the organs of the reproductive system). The ovary is where the egg yolks develop. They are then released and picked up by the oviduct for the "construction" of the rest of the egg. If the yolk is not picked up by the oviduct, it is shed into the body cavity of the hen. This phenomenon is called "internal laying," and typically such yolks are absorbed by the body. But sometimes such yolks become infected—the highly nutritious egg yolk is a good medium for bacteria. This condition is called egg peritonitis, and may result from secondary bacterial infection. Peritonitis causes a buildup of fluid in the abdominal area.
It is possible for a hen with egg peritonitis to die quickly or to become ill gradually. There is no treatment for egg peritonitis, although an antibiotic can be used if the condition is caught quickly.