Updated September 3, 2021
Essential facts (details below):
Causes Of A Swollen Belly In Cats
There are five likely causes for an enlarged abdomen in a young cat:
- Intestinal worms, especially in untreated kittens up to three months of age
- Pregnancy, in undesexed, free-roaming female cats
- Abdominal fat deposition, which is usually easy to identify
- Excessively large meals (swelling should come and go)
- Feline infectious peritonitis or FIP
However, only FIP is common in cats brought to the vet. This disease alone is estimated to cause the death of between 0.3 and 1.3% of cats worldwide.
Traditionally it’s been a death sentence. But it doesn’t have to any more. This picture shows the same cat after treatment.
Read on to learn more.
What Is FIP?
Feline infectious peritonitis is caused by a coronavirus that is one of the causes of diarrhoea in cats. For some, it’s a short-lived gastrointestinal or upper respiratory infection, whereas other cats become carriers. All you may notice is mild diarrhoea, but these cats will continue to pass large amounts of virus.
Coronavirus carriers can be easily identified with a faecal test, which both allows us to treat them better, and to isolate them from other cats. There is no risk from cats to people. Feline coronavirus is completely separate from the human strains such as COVID-19.
Virtually all coronavirus-positive cats never develop FIP. It’s a rare and tragic accident when it happens. Cats don’t catch FIP, they develop it. FIP occurs when that enteric coronavirus mutates into the FIP strain inside the infected cat.
FIP can happen to any cat but it’s more common in purebred and shelter kittens. That’s because these cats are kept at a higher concentration than strays, and therefore coronavirus is always more common in their environment.
Probably all the cats in contaminated premises catch coronavirus, most shake it off, around 13% become carriers and a smaller number get FIP. That’s no comfort if it’s one of your cats that’s affected.
Signs Of FIP In Cats
FIP comes in two forms, based on how the immune system responds. The effusive or wet form is most common, and is caused by the accumulation of large quantities of fluid in the abdomen and sometimes the chest.
Th wet form of FIP is mostly seen in kittens or young adults. Signs are:
- A swollen belly or trouble breathing
- Poor appetite and muscle loss
- Lethargy and fever
- A rough, staring coat
The cat pictured at the start is a good example. If you look closely you can see:
- Wasting of the back muscles and a loose collar from weight loss
- A swollen pot belly appearance and staring coat
If you noticed the yellowish skin, this cat is also jaundiced from high bilirubin levels. She’s much better now, thanks to the new treatment mentioned below.
The non effusive or dry form is less common and much slower. These cats also usually have a persistent fever, poor appetite, lethargy and weight loss. In addition, the FIP virus produces solid tumour-like granulomas around the body, most notably in the central nervous system and kidneys. Therefore, dry FIP is the great pretender. The symptoms will depend on the organ affected.
I have seen the dry form of FIP as either slowly growing abdominal lumps caused by enlarged lymph nodes or unexplained neurological disease. This could start as an unsteady gait, different sized pupils or a head tilt.
Diagnosis of FIP
The presence of a swollen belly in a young, sick cat is very suggestive of FIP, but to exclude other causes and confirm the diagnosis, further tests are always needed. These are:
- A complete blood count and biochemistry: expect to see elevated globulins and possibly anaemia and high bilirubin
- Abdominal tap: confirms the presence of fluid, which should be high in protein
- Specific FIP tests: a PCR test for the FIP mutation in fluid or tissue biopsies is positive in around 70% of cases
No cat owner should attempt to make a diagnosis on their own. There are now many reports of cats being needlessly treated with antivirals (see below) resulting from incorrect home-diagnosis.
The biggest problem with FIP diagnosis is that it’s often very hard be 100% certain of the dry form. The only definitive test is a positive tissue biopsy, but these are very hard to obtain. Without one the diagnosis is about building up a case, piece by piece.
Treatment Of FIP
Traditional treatment of FIP has been supportive, using good nutrition, anti-inflammatories and attention to secondary infections. Tragically, the most important treatment has been timely euthanasia.
However, new treatments are rapidly changing the outlook for kittens and cats with FIP. More than ever, it’s important to get an early diagnosis so you can begin what might be lifesaving treatment for some cats.
Have something to add? Comments are welcome below and will appear within 24 hours.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. These articles are from a series regularly posted on email and Twitter. Subscribe via email here to never miss a story!