By Dial A Vet Veterinary Team
A dog whose belly is steadily getting rounder, even while it loses weight and muscle, may have fluid building up inside the abdomen. Vets call this ascites or abdominal effusion. VCA Animal Hospitals notes that free fluid in the abdomen is always a cause for concern, because it is a sign of something else going wrong, such as heart, liver or kidney disease, bleeding or cancer. Finding that cause is what matters most.
Key takeaways
- Ascites is not a disease in itself. It is a sign of an underlying problem.
- Causes include right-sided heart failure, liver disease, low blood protein, bleeding into the abdomen, leaking urine, inflammation and tumours.
- A suddenly swollen belly, especially in a large deep-chested dog, may be bloat, which is a surgical emergency.
- Your vet will usually take a small sample of the fluid to find out what it is.
- Outlook depends entirely on the cause.
Is it fluid, fat or something else?
VCA explains that a dog's belly can look bigger for many reasons. Some are simple, such as weight gain, a heavy worm burden in puppies, or pregnancy. Others relate to illness, such as enlarged organs, Cushing's disease, hypothyroidism, a build-up of gas, or free fluid. Only a vet can tell these apart, often with the help of imaging and a fluid sample.
What causes fluid in the abdomen?
VCA describes several types of free fluid, each pointing to different problems:
Effusion. Fluid that escapes from body tissues and collects in the abdomen. This can develop with:
- Heart disease. VCA explains that in right-sided congestive heart failure, blood backs up in the vessels of the abdomen and the abdomen may fill with fluid. See congestive heart failure in dogs.
- Liver disease. See liver disease in dogs.
- Low blood protein. Very low levels of albumin can cause fluid to build up. Albumin can be lost through the gut with severe intestinal disease, or through the urine with kidney disease.
- Abdominal tumours.
- Inflammation of the abdominal lining.
Blood. Bleeding into the abdomen can follow trauma or surgery, or happen with bleeding disorders and some tumours.
Urine. Leaking urine usually means the bladder or urinary tract has been damaged, often after trauma such as being hit by a car. A blocked urethra can also cause the bladder to swell and possibly rupture.
Signs to watch for
- A swollen or rounded belly, which may develop slowly or suddenly
- Depending on the cause, other signs. With heart failure, for example, VCA lists tiring easily, coughing, breathing difficulty, an increased resting breathing rate, loss of appetite, pale or bluish gums, and weight loss with muscle wasting
When to see a vet
Go to an emergency vet now if your dog has:
- A belly that has swollen suddenly
- Trouble breathing
- Collapse, weakness or pale gums
- A swollen belly in a large deep-chested breed such as a Great Dane or German Shepherd. VCA describes gas build-up with twisting of the stomach (GDV) as life-threatening and needing emergency surgery.
- A swollen belly after a fall, fight or being hit by a car
- An unspayed female who is unwell with a swollen belly, as VCA notes pyometra (a uterus filled with fluid or pus) is life-threatening
Book a vet appointment soon if:
- Your dog's belly has been slowly enlarging
- Your dog has a known heart, liver or kidney condition and you notice any belly swelling
How vets find the cause
VCA explains that your vet will ask how long the swelling has been there, how quickly it appeared and whether anything happened beforehand. A full examination includes listening to the heart and lungs and gently feeling the abdomen. Tests may include:
- Blood tests and a urine test
- X-rays and ultrasound to look at organs and check for masses
- Heart tests, such as chest X-rays and an echocardiogram
- Abdominocentesis. A sterile needle is used to collect a small sample of fluid, which is sent to a laboratory. This shows whether the fluid is blood, urine or an effusion and gives clues to the cause.
- Fine needle samples or biopsies of any masses or enlarged organs
Treatment at a high level
Treatment targets the underlying cause. Heart failure, liver disease, kidney disease, inflammation, bleeding and cancer are each managed differently, and some problems such as GDV or pyometra need emergency surgery. Your vet will explain the options once the cause is known. Never give your dog human medicines such as fluid tablets, and do not restrict water unless your vet advises it.
Outlook
VCA notes the outlook varies with the cause. Conditions that can be managed often have a good outlook. Some emergencies can be corrected with surgery. Others, such as advanced heart disease, liver disease or cancer, may be manageable for a time but carry a poorer long-term outlook.
FAQ
Can ascites go away by itself?
Fluid in the abdomen always needs a vet assessment, because the cause needs treatment.
My dog has a heart condition. What should I watch for?
Ask your vet about monitoring your dog's resting breathing rate at home, and report any increase, coughing or belly swelling.
Talk with a vet
If you have noticed your dog's belly changing shape, a Dial A Vet veterinarian can help you work out how urgently to be seen. Book a Dial A Vet consult.
References
- VCA Animal Hospitals. Testing for Abdominal Enlargement in Dogs.
- VCA Animal Hospitals. Congestive Heart Failure in Dogs.
- VCA Animal Hospitals. Bloat: Gastric Dilatation and Volvulus in Dogs.
Disclaimer: Educational only. This page does not replace an examination or advice from your own veterinarian. If you are worried about your pet right now, contact your local vet or nearest emergency animal hospital.