Diagnosis – History and Clinical Examination

FIP is a very challenging diagnosis. Even for specialists, it can be impossible to be certain that FIP is the sole cause of a cat’s symptoms.

This means that it is easily possible to think that a cat has FIP when it doesn’t and also to think that a cat does not have FIP when it does. This applies in both specialist and general practice settings for many different reasons. Our service is here to help you and your vet understand the difficulties with this process. This is a very emotional time as a cat owner and this communication is incredibly important.

The information below is a guide and your vet will need to look at the whole picture to formulate a plan. None of these risk factors is certain and they just change the index of suspicion. Hence the challenge. 

We have tried to make this as simple as possible but it is NOT! That is why we are here to help you and your vet understand what a difficult process this is and to help you through piecing together this fuzzy diagnostic jigsaw! 

What things can give your vet a suspicion that your cat has FIP?

Signalment – Age/Breed/Sex/Lifestyle
FIP is more common in young (under 2 years old), purebred cats. It is less likely in cats over 5 years of age and in cats that lead an outdoor lifestyle. 

History – What you may have noticed.
Many cats with FIP will have a recent history of a stressful event. This can be confusing in two senses. Firstly, most young cats have had recent stressful events – changing home, vaccination, vet visits. And secondly, cats have been known to develop FIP after being investigated or treated for other conditions. So, it is possible for a cat to have both FIP and another condition.
Cats living in a multi-cat household or kittens from multi-cat household are at higher risk of having FIP. Being in contact with another cat with FIP or being the sibling of a cat with FIP both increase the risk of developing FIP.
Cats that have a recent history of fighting or having lived feral are less likely to have FIP.

Other features that may be seen in cases of FIP.

  • weight loss or failure to grow properly
  • dullness or lethargy
  • poor appetite
  • difficulty breathing
  • diarrhoea, vomiting and/or constipation.
  • swollen abdomen
  • wobbly gait, hypersensitivity
  • unable to walk on back legs or all four legs
  • Fits /seizures

Clinical Examination Findings

  • persistent or recurrent high temperature without response to antibiotics 
  • swollen abdomen possibly with fluid 
  • Fluid in chest/abdomen
  • masses in abdomen
  • heart sounds difficult to hear or absent
  • breathing with difficulty or rate elevated 
  • swollen or irregularly shaped internal organs
  • Swollen scrotum
  • Penis stuck out after erection – priaprism
  • jaundice- yellow mucous membranes of eyes/gums
  • pale mucous membranes – anaemia
  • Change in colour of the iris of the eye
  • Inflammation or bleeding in the eye or retinal detachment
  • Abnormal changes in pupil size
  • Flicking of the eyes from side to side or vertically
  • Head tilt to one side 
  • Wobbliness or unsteady gait
  • Fits or seizures
  • Behaviour changes or altered mental state
  • Skin nodules
  • Poor body condition (<5/9)

Presence of a heart murmur, arrythmia or crackles on listening to the lungs are features that point towards other diagnoses and are less likely to be present in cases of FIP. Similarly cats with signs of external ear disease or polyps are less likely to have FIP.