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Presence of Fluids in a Dog's Abdomen

Fluids in a Dog's Abdomen

If your vet has told you that your dog has ascites, he was using the technical term meant to depict the presence of fluids in a dog's abdomen, or more, free fluids exactly in the dog's peritoneal cavity. In order to better understand ascites in a dog's peritoneal cavity, it's important to learn more about this body part and the type of fluids accumulating there. Only your vet can diagnose your dog and find the underlying cause for a collection of fluids in the abdomen, but there are several possible causes for ascites in dogs, and unfortunately, many of them are indicative of significant, potentially life-threatening medical problems.

dog fluid abdomen

A Secondary Sign

The term ascites derives from the Greek word askítes which means "baglike."

It's important to recognize that ascites in dogs in not a primary disease but rather a secondary sign of disease.

This means that there is an underlying condition causing the fluids to accumulate in the dog's abdomen. To be more precise, the fluids are accumulating in the dog's peritoneal cavity.

The dog's peritoneum is a membrane that lines the abdominal cavity. It supports abdominal organs and acts as a channel for these organ's blood vessels, lymph vessels, and nerves.

Fluids collecting in the peritoneum may consist of bile, chyle, urine and blood along with exudative ad transudative fluids.

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 If your dog's abdomen is suddenly enlarged because of gas rather than fluids, and he is retching and restless, see your vet immediately. This can be a case of bloat which is life threatening if not treated immediately.


Determining the Cause

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Because ascites in dogs is a sign of an underlying disorder, veterinarians must run several tests in an attempt to recognize the primary disorder. The vet will start with a physical examination with careful listening of the heart and tapping of the abdomen.

Many vets start with blood work, including a complete blood count and chemistry profile.

While x-rays are helpful in many cases, in the case of ascites, they may provide little information due to the excessive density of fluids affecting visibility. Removing some fluid may help provide a better visual.

A preferable option is a dog ultrasound which can show the size and shape of the dog's abdominal organs. A biopsy may be performed during the ultrasound if the vet deems it helpful. It is best if the ultrasound is performed by a radiologist.

A sample of fluid taken from the abdomen (paracentesis) through a needle or small catheter can provide important insights on the underlying cause. This test is fast, simple and doesn't typically require sedation unless the dog is fractious and not collaborative.

It's important that fluid sampling is performed only after an ultrasound is done so to rule out a distended abdomen due to enlarged organs. This is to avoid poking organs with the needle.

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A List of Differentials

Differential diagnosis in medical terms relates to several conditions that may cause similar symptoms. It takes a process of elimination to rule out several differentials.

As mentioned, when it comes to fluids in a dog's abdomen, it's important finding the underlying cause for the distended abdomen due to fluid build-up.

A dog's symptoms may sometimes point out to an underlying cause, but it's important that the cause is confirmed though testing so to initiate the most appropriate treatment.

For instance, giving diuretics when a dog is suffering from a distended abdomen due to cirrhosis, may lead to more problems down the road. Following are some possible causes of fluids collecting in a dog's abdomen.

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History of Trauma

Internal bleeding may occur as a result of trauma and cause hemoabdomen, an abdomen filled with blood. A ruptured urinary bladder may cause ascites from the collection of urine leaking in the abdomen. Affected dogs will not urinate, may have nausea, vomiting, poor appetite and abdominal pain, explains veterinarian Dr. Drew. Other organs that may rupture spilling contents in the abdomen include the gallbladder and spleen.

A Heart Issue

Heart problems are one of the top causes for ascites. If the heart is failing from pumping well, fluid may build up and end up accumulating in the dog's abdomen and lungs. Generally, when the right side of the heart is mostly affected, the fluids accumulate in the abdomen; whereas, when the left side of the heart is affected, the fluid accumulates in the lungs, explains veterinarain Dr. Michael Salkin.

Heart conditions known for causing ascites include congestive cardiomyopathy, right heart failure, and congenital pulmonic stenosis. Sometimes, the heart may fail to work as it should when there is heartworm disease. In severe heartworm disease, the dog presents with and enlarged right ventricle along with enlarged pulmonary arteries. Heartworm disease left untreated can cause right sided heart failure and ascites may be present.

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A Liver Problem

Ascites can be a sign of advanced liver disease and is often a sign that the liver is failing and shutting down. With the liver no longer being able to detoxify the blood, toxins often accumulate making the dog feel poorly.

Liver conditions known for causing ascites include liver insufficiency, hepatitis,cirrhosis, and cholangitis. Symptoms suggesting liver disease include vomiting, appetite loss, increased drinking more and increased urination and jaundice (yellowing of the skin).

Low Protein Levels

Ascites at times can be caused by low levels of protein in the blood. Low blood protein (hypoproteinemia) can be caused by protein loss due to decreased production of protein from the liver. This tends to happen when there is low albumin,the most abundant blood plasma protein that is made by the dog's liver.

Albumin and the rest of blood proteins work by holding serum in the blood vessels, therefore when their numbers are low, fluid leaks out due to osmosis and this can cause leg swelling and fluids in the abdomen.

Low albumin happens either because the liver is not making enough or it is lost because of kidney disease or protein losing enteropathy, a condition where protein is lost from the dog's intestines, which leads to diarrhea, explains veterinarian Dr. Fiona.

A Possible Tumor

There are certain types of tumors in dogs that cause cause blood to collect in the dog's abdomen. One worrisome tumor that tends to bleed is a hemangioma (benign) or a hemangiosarcoma (malignant). When this tumor grows on the dog's spleen and it ruptures, it can cause bleeding into the belly, explains Dr. Fiona. 

Extensive blood loss from the presence of a ruptured tumor may cause anemia, pale gums, thirst, wobbliness, lethargy and even sudden collapse. Tumors of the liver, intestines, or lymph nodes are other possible causes for a distended abdomen in dogs.

Other Possible Causes

There are several other possible causes for an enlarged abdomen in dogs. For instance, peritonitis, the inflammation of the peritoneum, may lead intestinal contents leaking out.

Pyometra, the infection of a dog's uterus often seen in non-spayed female dogs may lead to abdominal distention due to the infection draining pus into the abdomen.

Problems with the proper clotting of the blood may cause bleeding into the abdomen either due to ingestion of rat poison or a bleeding disorder.

Portal hypertension, which is high blood pressure in the portal vein, is another potential cause that is associated with heart failure or with liver cirrhosis and can cause fluids to build up.

Removing the Fluid

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Regardless of the cause, treatment for dog ascites involves treating the underlying cause. Having an abdomen filled with fluid can be very uncomfortable to a dog and in severe cases may interfere with breathing due to the pressure placed on the dog's diaphragm. Some dogs find it uncomfortable to lie down.

Removing fluid from a dog's abdomen is done through a procedure known as abdominocentesis.

This procedure involves inserting a needle and drawing out the fluids. Dogs typically do not require sedation nor anesthesia as the only pain felt is the needle prick. However, it's important to recognize that the fluid is likely to recur and therefore this procedure only provides short-term relief, explain veterinarians Dr. Peden and Dr. Zenoble. 

Also, the sudden removal of large amounts of fluids may further compromise the affected dog. Too much fluid removed at once can cause abrupt albumin loss and circulatory collapse. If fluid must be removed for patient comfort, it's preferable removing it over several days.

How much does dog abdominocentesis cost? The cost for abdominocentesis in dogs can vary from one place and another. On average it can range anywhere between $70 to $200, but it's best calling around for more precise price quotes.


  • Iowa State University, Digital Repositary, Vol 44, Issue 1, Canine Ascites, W. Michael Peden, R. D. Zenobl
  • Textbook of Veterinary Internal Medicine, by Stephen J. Ettinger, Edward C. Feldman

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