Water belly is a colloquial term for a potentially serious condition in a hen called ascites. Ascites is the inappropriate accumulation of fluid within the body cavity of a hen. To understand this condition and know how to manage it appropriately, we first must discuss anatomy.
Normally, there is a membrane in the back half of the body around the intestines called the peritoneal membrane. There is a “potential” space formed by this membrane that typically has nothing inside it. However, when ascites occurs, fluid accumulates within this potential space.
A unique anatomical feature that is present in birds is the presence of air sacs. Air sacs are membranes that branch off the lungs and are present within the body cavity from the neck down to the intestines. Although they don’t participate in gas exchange, air moves through them to get to the lungs for gas exchange to occur. The air sacs are thin-walled and can change in size based on other structures next to them. This means if fluid accumulates in the belly, it can push on these air sacs, causing an alteration of air flow.
What & How?
Various disease processes can happen that can cause fluid to accumulate in the peritoneal space. But there are four basic pathophysiologic mechanisms of how it occurs.
Decreased Osmotic Pressure
The first to discuss is known as decreased osmotic pressure. There is a process known as osmosis that governs the flow of fluids across a membrane. Large particles on one side of a membrane cause fluid to want to stay on that side of the membrane with them.
In the case of blood vessels, the protein called albumin acts as this large particle. Albumin protein is necessary to help maintain fluid appropriately within blood vessels. If there isn’t enough of it, fluid can leak out of blood vessels. Problems such as liver disease or gastrointestinal disorders could lead to lower levels of albumin in the blood, thus resulting in fluid to accumulate within the intestinal peritoneal cavity.
Hydrostatic Pressure
The second disease process that causes ascites is an increase in hydrostatic pressure. We can think about the heart and blood vessels as essentially a tubing system with the fluid that is running through it being blood. In various forms of heart disease blood may not be being pumped around the body effectively, leading to pressure alterations. This increased hydrostatic pressure then results in fluids leaking out of blood vessels and accumulating within body cavities or within organs.
Vasculitis
The third way ascites develops is by a process called vasculitis. This is where blood vessels are inflamed for an underlying reason, and it makes the junctions between the cells that line the blood vessels not fit together as well. This causes fluid to leak out of blood vessels. Underlying disease processes that cause inflammation include infectious diseases, local irritants and other problems. Various reproductive problems can lead to vasculitis including things such as egg yolk peritonitis, an impacted oviduct, cystic ovarian disease and reproductive tract cancers.
Impaired Lymphatic Drainage
Lastly, the fourth pathologic process that leads to ascites is impaired lymphatic drainage. The lymphatic system in the body is involved in helping fluids that are out in tissues to be taken up and put back into the vascular system. This sort of system is more developed in mammals, but it’s still present to a minor degree in birds.
When a hen develops ascites by one of these routes, the same problem and signs will occur. If a small amount of fluid accumulates it may not cause her to have any signs. However, if a large amount of fluid accumulates this ends up putting pressure on her abdominal organs and leads to compression of air sacs.Signs she can have associated with this include things such as respiratory distress, open beak breathing, panting and becoming easily winded after running around. Some signs are very vague, and she may just be less vocal, acting tired or not eating as well. If you feel her bottom, she may have a very rounded, full-feeling belly. More than likely, she’ll not be laying during this time, but it’s possible that she may still try.
What Should You Do
If you find that your hen has a round-feeling bottom, do not try to treat her yourself without knowing why her belly is the way that it is. The reality is, that rounded belly could be ascites, but it could be any number of other problems as well. A mass, an enlarged organ or a large amount of fat can all feel very similar, even to the trained professional who feels chicken bellies every day! You really must get a veterinarian to do a thorough physical exam and some testing to know if ascites is present.
Your veterinarian may want to do a few different tests to tell what is going on in the belly of your hen. I recommend doing one of two tests to diagnose ascites.
The first is an ultrasound. This is very quick and allows the veterinarian to immediately tell if there is any fluid present. It also allows them to know exactly where they need to drain the fluid from. Sometimes this diagnostic test also allows the veterinarian to tell which of the previously described pathologic causes is behind why the ascites developed. Sometimes it does not.
The other test the veterinarian may want to do to diagnose ascites is to place a needle into the abdomen to see if they can draw fluid out. If they can get fluid out this is abnormal and ascites is present!
Now here is where the dilemma comes in that each individual owner needs to decide. Is your chicken a production animal that is a part of your farm? Or is your chicken a pet?
If your chicken is a production animal, you need to seriously consider how humane it is to keep on going with this bird. Once ascites is diagnosed, to treat it appropriately, you must find out why it is happening. This allows you to get the most targeted, appropriate and effective treatments and care done. However, this can become expensive quickly. Your bird may need blood work, cultures, cardiac ultrasounds (echocardiograms) and even exploratory surgery to figure out why ascites is happening.
Yes, all this can be done in a chicken but are you prepared to do it?
If your bird is a production animal, these diagnostics may not be practical. And the other harsh reality that needs to be discussed is that most of the causes for ascites are serious ailments that do not have good outcomes in the long run. Yes, treatments can be done, but not all problems are fixable.
For those problems that can’t be fixed, treatments to keep a bird comfortable and improve quality of life may be able to be done. However, it may be prolonging the inevitable. If you don’t want to do treatments or diagnostics, it’s OK and, even more importantly, humane to consider euthanizing or culling that individual.
If your bird is a pet or has become one over time, you may want to work with your veterinarian and do some of the previously mentioned diagnostics. Once the cause for ascites is determined, treatment options need to be discussed.
In many chickens, the main cause of ascites is a reproductive disorder. Many people think the only cause of ascites is egg yolk peritonitis. This is simply not the case. As we learn more about avian medicine and do more diagnostics, we’re finding that many other forms of reproductive tract pathology can cause ascites. I have personally seen more birds with cancer of the reproductive tract causing ascites than egg yolk coelomitis cases. 
Treatment
Depending upon what your veterinarian determines, the cause of the ascites will determine what treatments need to be done.
If your bird happens to have:
- Liver Disease Causing Ascites: Liver support medications may be needed.
- Heart Disease: Heart medications are in order.
- Egg Yolk Coelomitis: Anti-inflammatories and possibly antibiotics are needed.
- Cancer of The Reproductive Tract: Sometimes hormone therapies, pain medications, anti-inflammatories and omega-3 fatty acids are recommended.
- An Impacted Oviduct: She may need to be spayed.
Although treatments may vary, one treatment that all forms of ascites will have in common is the need to have fluid drained from the belly. This treatment can give your bird some immediate relief. If you’re lucky and it’s a simple case of egg yolk peritonitis, one draining may be all that is needed.
Yes, you read that correctly. I said you’re lucky if it’s egg yolk peritonitis, and you may have this problem only once. You’ll read in many places that egg yolk peritonitis is a death sentence and, if it causes ascites once, it will just keep happening. The reality is that information is based off the assumption that all causes of ascites are from egg yolk coelomitis. And as we have discussed throughout this article they simply are not.
Yes, many causes of ascites will be repeated problems (for example liver disease, heart disease, reproductive tract cancers, cysts), but egg yolk peritonitis doesn’t have to be one of those that leads to repeated fluid build-up. In fact, every time I have worked with a bird that has had ascites reoccur, it has had some other cause for the ascites than egg yolk peritonitis. So, consider that fact if you encounter this problem in your hen and she develops this as a reoccurring issue.
One problem that owners have asked me is if they can drain their bird’s belly of fluid on their own at home. My answer for this is that you really need to work with your veterinarian and have them tell you if this is OK to do with your bird or not. In many cases, it won’t be.
Not only does the fluid draining need to be a sterile procedure, it needs to be done in the correct location of the abdomen. If the incorrect location is poked with a needle, it can cause problems and be painful. One owner informed me once that she knew of someone online who would put needles into their hen’s belly and let them walk around and drain the fluid on their own. I must say that this is a highly inappropriate and inhumane to do.
One problem with this is that leaving a needle in the body is leaving a hole in the body that bacteria can climb up into, which could result in an infection. That’s a quick way to make your bird sicker and die faster. The other problem with this is as the fluid drains that needle will start to scrape against the internal organs. This could lead to lacerations on organs and damage, and it must also be highly uncomfortable.
Please don’t do this to your chicken. Get help from your veterinarian if you want to treat your bird. And if you don’t, please consider humane euthanasia or culling.
Ultimately, most of the diseases that cause ascites can become chronic problems that require lifelong management or medications. Occasionally, you may get lucky and have it be a one-time problem. However, working with your veterinarian can help you to determine what the cause is for your bird. And it can help you to determine what you need to do to treat it.
Remember: It’s OK to say you don’t want to treat the problem. But if you don’t, please do what is right by the bird. Don’t let it suffer.
This article originally appeared in the Nov./Dec. 2023 issue of Chickens magazine.
