Feline Lower Urinary Tract Disease

Tabby cat standing on pavingFeline lower urinary tract disease (FLUTD) is a common syndrome which affects the bladder and/or urethra in cats.  It may also be known as ‘cystitis’.  It can be very distressing for both cat and owner.

There are several potential causes of FLUTD but the most common is Feline Idiopathic Cystitis (FIC).  This can be a very challenging condition to manage and is caused by an inflammatory reaction in the bladder and urethra which has no obvious cause.

How can I tell if my cat has FLUTD?

Cats with lower urinary tract disease can show a variety of clinical signs, although most are obviously urine-related.

  • Increased frequency and difficulty passing urine – the cat may visit the litter tray frequently and strain but not pass very much urine.  They may also cry when passing urine.  In severe cases, your cat may not be able to pass urine at all.  This requires emergency veterinary attention.
  • Blood in the urine – sometimes this is very obvious with the urine being discoloured, but sometimes this is only detected with a laboratory examination.
  • Cross Siamese cat hissingUrinating in inappropriate places – the inflammation can give a real sense of urgency to urinate so your cat may not be able to make it outside or to the litter tray.  Some cats may spray urine because of their discomfort.
  • Overgrooming – because of the discomfort in the bladder, some cats will lick their tummy or rear end excessively causing baldness.
  • Behaviour changes – because of their discomfort, cats may become more irritable and aggressive than normal, as well as apparently losing their house training.

Causes of FLUTD

  • Tabby and white cat walking onto path from grassIdiopathic cystitis – this is the most common cause but it is a diagnosis of elimination, meaning that all other causes must be ruled out first.  The inflammatory cells produced can lead to urethral plugs which can block the urethra, making it difficult to pass urine.
  • Bladder stones – stones can cause irritation as well as blockages.  There may be one large stone or lots of smaller ones.  The most common types of stones in cats are struvite (magnesium ammonium phosphate) and calcium oxalate.
  • Bacterial cystitis – caused by a bacterial infection in the bladder.  This is most common in older cats and is often due to an underlying disease which causes the urine to be more dilute or sugary, for example kidney disease and diabetes.
  • Tumours – bladder tumours are rare in cats but can occur.  Transitional cell carcinoma is the most common.
  • Anatomical defects – these are rare but can occur after trauma or surgery to the lower urinary tract.  Narrowing of the urethra (strictures) due to scar tissue can make it difficult for a cat to produce a normal flow of urine.

How is FLUTD diagnosed?

A diagnosis of FLUTD is made simply by taking a history and examining the cat.  Determining the underlying cause of the problem will involve further investigation.

Urine sample
Urinary crystals
Urinary crystals

A urine sample is really useful to determine the most likely cause.  In mild cases of FLUTD, it may be the only investigation needed.  The concentration of the urine sample is key.  If the urine is concentrated, FIC is the most likely cause.  If the urine is quite dilute, bacterial cystitis is most likely and investigations into the underlying cause of this should be started.

If bacterial cystitis is suspected, sending a sample of urine taken directly from the bladder to the laboratory for culture is advisable before starting on antibiotics.

Examination of the urine under the microscope may reveal urinary crystals which could indicate that bladder stones are more likely.


X-rays should be performed if the problem is recurrent, or if there is evidence of an obstruction.  Some stones are very obvious on x-ray but others need the addition of a contrast material.  Contrast is placed into the bladder using a catheter.  This will also allow any narrowing or tears in the bladder or urethra to be detected.


Ultrasound examination of the bladder is also helpful to see stones and is the best way of seeing bladder tumours.

Related conditions

Chronic kidney disease

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