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bloated bellies: dr. kim smyth explains a condition called ascites

  • Dr. Kim
  • Posted by Dr. Kim Smyth on
    Staff Veterinarian and Pet Health Writer of Petplan


Ascites is the buildup of fluid in the abdomen.  The fluid accumulates in the space between the organs and over time it can cause abdominal distention.  As fluid accumulates, it can also put pressure on the diaphragm, making breathing a challenge for those affected by ascites. 

Ascites is not uncommon in dogs and cats, and it has plenty of underlying causes.  If your pet has ascites, you can bet that there is a significant and serious underlying problem causing it.  Below are some of the most common reasons for ascites:

Right-sided heart failure.  While left-sided heart failure often results in fluid buildup in the chest, right-sided heart failure causes ascites.

Chronic liver disease.  Ascites can occur due to decreased protein production by the liver or by increased resistance to blood flow in the liver.

Peritonitis.  Inflammation or infection of the lining of the abdomen can cause fluid buildup.

Abdominal tumors.  Decreased lymph flow or fluid production by the tumor can both contribute to ascites.

Protein-losing enteropathy.  This gastrointestinal disorder causes protein to be lost through the stool. Low blood protein levels lead to ascites, just as in the case of chronic liver disease.

Feline infectious peritonitis (FIP).  In young cats, FIP commonly causes ascites.

While we generally think of ascites as a buildup of clear fluids called transudates and exudates, strictly speaking, ascites is a buildup of any fluid, so two additional causes can be added to the list.

Hemorrhage.  Blood in the abdomen (or hemoabdomen) can be caused by trauma, like when a pet gets hit by a car, tumors in the abdomen, or blood clotting disorders (including rodenticide ingestion).

Urinary bladder rupture. If a urinary blockage goes untreated, eventually the patient will succumb or the bladder will rupture, leaving the abdomen full of urine.

Diagnosis of ascites can sometimes be accomplished via physical exam only, as an uncomfortable distended abdomen is likely to be found.  However, because ascites is only a symptom and not a disease, further diagnostics will need to be done to determine the underlying cause.  Blood work, a urinalysis, and x-rays will proved a good data base for identifying what might be causing ascites.  Taking a sampling of the abdominal fluid can also help guide your vet towards an underlying cause.

The treatment and prognosis for ascites varies quite a bit depending on the underlying cause.  If the condition can be cured or corrected, ascites can resolve.  But sometimes ascites is present at the end stage of diseases that cannot be cured, and when this occurs, we can only try to manage ascites rather than resolve it.

Treating the underlying condition, such as heart or liver failure, with appropriate medications can decrease the amount of ascites present.  Diuretics are the mainstay of medical therapy for ascites, but your veterinarian may recommend a special salt restricted diet.  In cases of ascites where a large volume of fluid is present in the abdomen, medical therapy may not be adequate to provide relief for your pet.  In these cases, fluid can be removed from the abdomen in a procedure called an abdominocentesis.  Removal of fluid can resolve discomfort from a distended abdomen and allow your pet to breathe easier.

Ascites always has an underlying cause, and until that cause is addressed, it will continue to occur.  In the case of chronic or end-stage diseases, ascites will likely continue to occur even with treatment, but the goal of treatment is to keep your pet comfortable. 

If your pet has ascites, talk with your vet about quality of life issues and how to help your pet live the best way while managing his condition.

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Chris AshtonCo-Founder and Co-CEO of Petplan Pet Insurance
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