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Ascites (Free Fluid in the Abdomen) in Dogs and Cats

The normal abdomen houses organs that are bathed in a certain amount of intra-abdominal fluid.  This fluid helps to maintain sterile environment for the organs and helps to fight infection, keep and cells and tissues moist and healthy, and promote cellular renewal and tissue repair.  When free fluid in the abdomen accumulates that is excessive and even distends the patient, this is referred to as ascites.
Ascites is really not a disease in and of itself, but a syndrome or clinical sign that arises secondary to some other primary disease process.  There are certain diseases that can commonly lead to ascites that I will outline here:

1.) Diseases of the liver may lead to an increase in the pressure of its major venous drainage, a blood vessel known as the hepatic portal vein.  This subsequent increased pressure leads the leakage of the serum portion of the blood through fenestrations in blood small blood vessels normally utilized for nutrient exchange.  Another consequence of liver disease that can contribute to ascites is the liver not having the ability to synthesize adequate amounts of the serum protein albumin.  In addition to being a major carrier protein in the blood stream, albumin also carries a charge that keeps the aqueous (water) portion of the blood stream in the blood vessels at the level of the capillaries, small blood vessels utilized for nutrient exchange at the tissue level.  Insufficient amounts of albumin therefore will lead to extravasation of the aqueous portion of the blood at the capillary level and collect in body cavities such as the abdomen.  Liver diseases that can lead to ascites include: portosystemic shunt, chronic active hepatitis, cholangiohepatitis, cirrhosis, and canine infectious peritonitis.

2.) Congestive heart disease – Left sided heart failure commonly leads to fluid in the lungs, while right sided heart failure more commonly tends to lead to fluid accumulation in the abdomen.

3.) Kidney failure – The large serum protein, albumin, is normally unable to escape the blood stream via the kidneys’ individual filtration apparatuses within the kidneys known as nephrons.  In cases of kidney failure where disease extends to nephrons, albumin can be lost in the urine.  Excessive loss of albumin leads to albumin deficiency and a syndrome that result in line with albumin deficiency that occurs with liver disease: ascites.

4.) A number of infectious diseases can cause abdominal effusions, the most common of which in veterinary medicine is feline infectious peritonitis (FIP).

Free fluid in the abdomen can be treated by tapping the abdomen utilizing a a drainage technique called abdominocentesis.  Some cases will respond to treatment with a diuretic depending on the cause of ascites, however, severe ascites usually requires abdominocentesis to manage initially.  Further management of ascites involves treating the primary disease that is causing it.

Roger Welton, DVM

President Maybeck Animal Hospital

CEO, Founder, Web-DVM

9 thoughts on “Ascites (Free Fluid in the Abdomen) in Dogs and Cats

  1. prast says:

    Thank you Dr Roger Welton

  2. Rachel says:

    I took my one year-old cat to the vet for what seemed to be bladder stones and now he has fluid build up in his abdomen what is not urine. His bladder was flushed to remove the stones. He vomited several times after the procedure and only ate a little food by syringe in what has now been 3 days. Could the procedure to flush the bladder rupture it causing ascites?

  3. Lynn Roe says:

    My Chihuahua has belly bloat, fluid in her abdomen.I’m giving her diuretics, also Albumin.I’ve been doing this for 2 days. Today she’s feeling a little better. I think I’m on the right path. Advice? Comment

    • Thanks, Judith says:

      My 10 year old chihuahua has the same thing. She has low blood albumin, and the ascites and weakness has been going on for two months. She had an abdominal ultrasound, and the vet thought she saw a stomach tumor, but the dog is eating fine, does not vomit, and her stools look normal. She is uncomfortable due to the ascites, and waddles, and is not as active, but her water intake and voiding appears normal. If she has stomach cancer, I doubt she would even be eating, or walking around. Tomorrow, I will have some fluid drained and analyzed, take some pressure off her. More blood work to vheck for kidney or liver disease. I hope this is a treatable disease, rather than cancer.

  4. Lynn Roe says:

    Thank you, even if you don’t answer me. I don’t want my Chihuahua Blue Bell to die.

    • Judy says:

      I am in the same boat. We have a chihuahua named Pie. Very sweet girl, a real character, whose belly gradually distended, and she got weaker, not able to jump up on the chair any longer. My husband thought she was getting fat, but I knew something was very wrong. Her blood work was all good, except for low blood albumen. Her stool is negative for parasites. We had an ultrasound done, and there is a tumor in her stomach. So far, it has not obstructed her stomach, and she eats without vomiting. The vet offered to do a biopsy to see if it is malignant, or benign, or ? She said removal of them tumor probably would result in Pie dying, since her blood protein is low. To open her belly, and all the fluid come out would make her unstable and go into shock. A biopsy of her stomach would cost 1500 dollars, and whether it is benign or cancer, does not really matter. We don’t want to put her through chemo. She is pretty comfortable now, enjoying her food, and until she can’t keep it down, just will love her till we have to say goodbye. Good luck to you!

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