Egg Yolk Peritonitis in Backyard Chickens

What is egg yolk peritonitis?

Egg yolk peritonitis or coelomitis occurs when yolk from a developing egg, an incompletely shelled egg, or a ruptured egg is deposited within the body cavity, referred to as the abdominal coelom. It is commonly diagnosed in laying hens. Normally, the developing egg passes from the bird’s single ovary (generally on the left side of the body) into the single, tube-like oviduct (salpinx), and then out of the body, through the vent, as a fully shelled egg. With egg yolk peritonitis, yolk material is released into the coelomic cavity instead of the salpinx, causing considerable inflammation of the peritoneum (the thin layer of tissue lining the coelom and internal organs). It also typically causes fluid to develop within the coelom.

The reproductive tract and intestinal tract both empty out through a common exit (the vent), so there are instances where bacteria migrate up the salpinx to the ovary. In these cases, the yolk material can become infected with bacteria from the intestinal tract (most commonly Enterococcus or E. coli).  In rare cases, bacteria from the coelom may enter the bloodstream, causing sepsis, a secondary, potentially life-threatening infection that can infect critical organs such as the kidneys, liver, and heart.

How will I know if my hen has egg yolk peritonitis?

Hens with egg yolk peritonitis will stop laying eggs or lay only soft-shelled, thin-shelled, or misshapen eggs. These hens will generally be less active, choosing to sit in the nest box more, rather than to walk around, and they may eat less than normal. Affected hens may have visibly distended abdomens due to the presence of fluid in the coelom and may have difficulty breathing from the pressure of the fluid on their respiratory tracts.

What causes egg yolk peritonitis?

Egg yolk peritonitis may occur when a single egg does not form properly or it may develop secondary to other underlying reproductive diseases, including inflammation of the oviduct (salpingitis), impaction of the oviduct with multiple abnormally formed eggs, ovarian cysts, ovarian cancer, or twist of the oviduct preventing normal passage of eggs through it. Certain viral diseases, such as Marek’s disease virus or avian leukosis virus, may affect the reproductive tract directly or cause an immune deficiency state that allows bacteria to infect the reproductive tract.

How is egg yolk peritonitis diagnosed?

If your chicken shows any signs of egg yolk peritonitis, outlined above, she should be examined by a veterinarian familiar with chickens as soon as possible. Your veterinarian will perform a complete physical examination and may palpate (feel with fingertips) fluid or soft-shelled eggs in the coelom. Your veterinarian may also note if your bird is breathing quickly or with increased effort.

Typically, your veterinarian will perform blood tests, including a complete blood count (CBC) that may show an elevated white blood cell count, indicating inflammation or infection. Your veterinarian may also perform coelomocentesis to draw off fluid present in the abdomen. In this process, a small needle is inserted through the skin on the abdomen and into the bird’s coelom, typically between the base of the keel (breastbone) and the vent. The fluid may be submitted to a referral laboratory for microscopic analysis to determine whether bacteria are present and, if so, which antibiotics will be most effective for treating the infection.

Your veterinarian may also take radiographs (X-rays) or perform an ultrasonographic examination to further assess the inside of your bird’s coelom and to confirm the presence of fluid and/or unshelled or partially shelled eggs.

How is egg yolk peritonitis treated?

Mild cases of egg yolk peritonitis, in which there is no secondary bacterial infection or underlying reproductive disease, may require only supportive care, such as supplemental hand feeding and anti-inflammatory medication.

With more advanced cases in which infection is present, your veterinarian may prescribe oral or injectable antibiotics. More aggressive supportive care may be required, such as hospitalization for fluids injected subcutaneously (under the skin) or intravenously (in a vein), oxygen therapy, and repeated drainage of coelomic fluid. In the most advanced cases, surgery (called salpingohysterectomy) may be necessary to remove the offending egg(s) and oviduct.

If a bird has reproductive disease with secondary egg yolk peritonitis caused by either Marek’s disease or avian leukosis virus, it is usually fatal, even with treatment.

Many avian veterinarians treating egg yolk peritonitis will also administer a hormone, either through injection or as a slow-release implant under the skin. This hormone temporarily prevents further egg laying that would worsen the hen’s already compromised condition.

While egg yolk peritonitis may be life-threatening, with proper treatment, some chickens with this condition can be treated successfully.