There are a number of reasons a chicken's abdomen could be bloated or swollen, so it's important to get a proper diagnosis from a veterinarian or poultry specialist.
A bloated or swollen abdomen in a chicken could be a symptom of any number of illnesses or health issues, several of which directly or indirectly affect the hen’s reproductive system. In veterinary medicine, there is rarely one cause of a condition, so we usually begin with a list of differential diagnoses and use lab tests and physical exams to differentiate. With this in mind, your best course of action is to reach out to your county-extension poultry personnel or veterinarian for help in differentiating the various causes of a swollen abdomen. Veterinarians can perform a physical exam and run diagnostic tests, including X-rays, to distinguish between fluid and solid contents in the abdominal cavity.
Approach the diagnostic process with a clear sense of the animal’s financial value to your operation: Although some services might be available free of charge through a land-grant extension office, the expense of some diagnostic tests and treatments can add up quickly. While it’s always worth your time and money to identify a bacterial or viral infection that could potentially impact more than one member of the flock, this might not be the case with a condition that only affects one hen.
Poultry keepers who keep genetically improved breeds, bred for high egg production, might see these problems more frequently in their flocks, as production breeds—most of which are usually kept for 12 to 18 months in commercial settings—do not have the genetics to support three to four years of egg-laying. The risk of reproductive disorders increases with age in layers. These afflictions aren’t exclusive to production breeds, however—they can show up in any small-scale flock. Although it’s best to have a veterinarian examine your chicken, here’s a short list of differential diagnoses.
1. Ascites (aka Water Belly)
Fluid can accumulate in the abdominal cavity, secondary to heart disease or tumors in the heart and liver. Fluid in the abdominal cavity is usually accompanied by respiratory distress and cyanosis (bluish color) of the combs and wattles. There is no treatment for ascites.
Several diseases, such as Marek’s disease, lymphoid leukosis and various adenocarcinomas, cause tumors and enlargement of a chicken’s internal organs, such as the liver, which might, in turn, distend the abdomen. Tumor diseases tend to be chronic, and affected chickens slowly suffer weight loss and decreased appetite. All day-old chicks should be vaccinated for Marek’s disease at the hatchery. Lymphoid leukosis can be transmitted from hens to developing embryos; therefore, disease-free chicks should be purchased from reputable hatcheries. There is no treatment for tumor diseases.
3. Fat Deposition
Extremely obese hens have a thick fat pad that can distend the lower abdomen. Obesity, normally caused by high-energy diets, also predisposes chickens to a condition called fatty liver hemorrhagic syndrome, where the liver is infiltrated with fat and can contribute to abdominal distension. The syndrome causes acute death in chickens when blood vessels in the liver rupture and cause internal bleeding. It’s seen increasingly in backyard and pet chickens that are fed table scraps high in calories. It’s also very common with small-scale flocks fed free-choice via feeders. Chickens should be fed a well-formulated and appropriately portioned diet to avoid FLHS.
4. Cystic Oviduct
Normally, only the left ovary and oviduct of the hen are functional, but sometimes, the right oviduct is functional and becomes cystic. The cysts appear in a range of sizes, and overly large cysts can distend the hen’s abdomen and compress internal organs. Your veterinarian might be able to drain the cyst nonsurgically using a sterile syringe and needle.
5. Impacted or Egg-Bound Oviducts
These oviductal disorders are seen in obese hens, older hens or pullets that come into lay too early. The oviduct becomes blocked by an egg or a mass of broken eggs and eventually eggs are pushed back into the body cavity as the hen continues to lay. Affected hens walk like penguins when the eggs in the abdomen are excessive.
There is no technical difference between impaction and "egg-bound;” however, I don’t like using the term egg-bound, as it’s more appropriate for what happens in pet birds, such as parrots, where one fully formed egg is stuck in the oviduct.
In chickens, the obstruction can result from several lodged eggs or a mass of broken shells, shell membranes, or a mass of yolk and egg white, and the result is the same. When impaction occurs in the front part of the oviduct (aka uterus), which is usually the case, eggs enclosed by shell membranes might be found in the abdominal cavity. This indicates that eggs continued to form but were refluxed back into the peritoneal cavity. The prognosis for affected hens is poor. The use of antibiotics might prolong an affected chicken’s life for a few months, but it will eventually die from the condition.
This inflammation of the oviduct occurs frequently and can be introduced through the cloaca by various means, including pecking. The most common infection is by E. coli bacteria. In later stages of the condition, the oviduct and abdomen become distended due to masses of foul-smelling, cheesy contents in the oviduct. The cheesy masses are sometimes mixed with egg contents; as a result, salpingitis can frequently be confused with an impacted oviduct.
A chicken with salpingitis can remain healthy for a long time—until the late stage when oviductal contents start to impinge on vital organs. The chicken then becomes sick, refuses to eat and slowly declines. Antibiotics seem to help only temporarily, and while some veterinarians might attempt surgery, the chicken’s oviduct is so friable that the procedure is unlikely to be successful. Affected birds will die.
About the Author: Jarra Jagne, DVM, DACPV, senior extension associate, Veterinary Support Services, Cornell University Animal Health Diagnostic Center
Dr. Lyle G. McNeal is a livestock specialist in the Department of Animal, Dairy and Veterinary Services at Utah State University.
This article originally appeared in the May/June 2013 issue of Hobby Farms.