Feline Lower Urinary Tract Disease

Feline Lower Urinary Tract Disease (FLUTD) is not a specific disease. This rather is the term used to describe conditions that can affect the urinary bladder and/or urethra (the lower urinary tract) of cats.

Feline Lower Urinary Tract Disease (FLUTD) encompasses feline UTIs (Urinary tract infections).

Problems that affect a cat’s lower urinary system often prevent the bladder from emptying correctly. Other problems may even cause fatal blockage of the urethra (the tube connecting the bladder to the outside of the body). 

  • Dysuria – difficulty or painful urination – strain to pass urine, sometimes cry out if it is painful.
  • Pollakiuria – increased frequency of urination – infection and inflammation of the bladder and urethra will cause irritation and the increase the need to urinate more frequently.
  • Haematuria – blood in the urine – this can also occur with infections and inflammation.
  • Periuria – urinating outside the litter-box and in unusual or inappropriate places.
  • Over-grooming – because of the pain and irritation in the bladder and urethra, some cats may start to over-groom and lick around their genital area.
  • Behavioural changes – loss of litter-box training, aggression or irritation.
  • Stranguria – blockage to the urethra – cats will strain to urinate and try to pass urine but could not eliminate it. Male cats are more likely to become blocked, as their urethras are longer and narrower than in female cats.

Two divided feline groups

  • Cats with a urethral obstruction (males);
  • Cats that are not obstructed but are displaying clinical signs (male, female).

A cat with urethral obstruction is ALWAYS AN EMERGENCY!

The “Blocked Cat” is a cat with a urethral obstruction from urinary stones or urethral plugs. Most common in neutered male cats eating only dry food.

Cats with urethral obstruction

  • Most obstructions are the result of urethral spasm and/or plugs.
  • Urethral spasms -> inflamation and irritation of the urethral musculature -> leakage of plasma, including albumin and bicarbonate, into the urine.
  • This provides the protein needed for matrix formation and increases the urine pH, promoting the formation of struvite crystals.
  • Urethral obstruction typically occurs in male cats between 1 and 6 years of age.
  • Cats may strain unproductively to urinate and may cry out during the attempt. Some pet parents mistake this attempts with constipation.
  • They are licking the genital region (frequently observed), hide in a secluded area.
  • Diagnostic: Urinalysis and urine culture can be performed on urine collected by cystocentesis before urethral catheterization or via the catheter after relief of the obstrucion. Serum creatinine and BUN allow assessment of the degree of azotemia. Serum potassium levels and an ECG tracing should always be performed in depressed cats to assess cardiotoxicity associated with hyperkalemia. Affected male cats may be azotemic, hyperkalemic, acidosis, or bradycardic.
  • Cats with obstructed Feline Lower Urinary Tract Disease (FLUTD) have an enlarged and firm bladder.

Non-obstructed cats

  • Not urinating in designated spaces and vocalizing during urination is a clinical sign that often initiates the visit to a vet.
  • As vets, we must differentiate cats with FLUTD from those with behavioural issues.
  • Other possible causes include uroliths, UTIs and neoplasia.
  • Signs: stranguria. pollakiuria, hematuria, dysuria.
  • Diagnostic: along with diagnostic imaging, laboratory data should include a CBC, serum chemistry panel and urinalysis. The CBC and chemistry panel help rule out systemic disease. Crystalluria is a common urinalysis finding and it is unlikely to be the cause of the condition; rather it is most ikely a result of an inflamation.
  • Cats with nonobstructed Feline Lower Urinary Tract Disease (FLUTD) usually have a small and thickened bladder wall.

Once called Feline Urologic Syndrome (FUS), Feline Lower Urinary Tract Disease (FLUTD) is not a singular problem, but a collection of clinical symptoms that may have more than one possible causes.


Urinalysis – Collecting a urine sample to analyse (examine microscopically and perform bacterial culture to rule out bacterial infections) is an important step. Your vet may obtain a urine sample by placing a very fine needle directly into the bladder (cystocentesis).

All cats presenting for FLUTD should have diagnostic imaging (X-rays) or even better, an ultrasound performed. This will allow us to inspect the urinary tract for uroliths, anatomic malformations or neoplasia.

Biopsies – sometimes, obtaining a biopsy (tissue sample) of the bladder wall may be needed, especially if an underlying tumour is suspected. 

Underlying causes and treatment of Feline Lower Urinary Tract Disease (FLUTD):

1.Urolithiasis (bladder stone)

  • The two most common types of stone, depending on their composition, are “Magnesium Ammonium Phosphate” (or “Struvite”) and “Calcium Oxalate”. These are the most frequent (80-90%) but others may also be seen.
  • Treatment: Some types of stone, such as Struvite Stones, may possibly be dissolved by simply changing your cat’s diet with a special food available at your vet; this can also prevent them recurring.
  • Other stones, such as Calcium Oxalate, cannot be dissolved, so your cat will need surgery removal of the stones. Feeding you cat also with a wet (tins or sachets) diet and not only dry food, will help increase the water intake which can also be helpful in preventing stone recurrence.

2.Bacterial infection

  • Bacterial cystitis (bacterial infection of the bladder) is the most common cause of lower urinary tract disease, but is relatively uncommon in cats.
  • Bacterial cystitis tends to be seen more often in older cats.
  • Symptoms of FLUTD include frequent or painful urination, bloody urine and frequent licking of the urinary opening. If the cause of these symptoms cannot be determined, the cat is considered to have bladder inflammation (cystitis).
  • Treatment: antibacterial therapy (made on the basis of bacterial culture and sensitivity testing of the bacteria).

3.Urethral plugs (urethral stones)

  • Sometimes, an obstruction of the urethra in male cats may occur as the result of a ‘Urethral Plug’.
  • What is this “Urethral Plug”? An accumulation of proteins, cells, crystals and debris in the urine that combined together, forms a plug that cannot be passed.
  • A blocked urethra in a cat can cause acute kidney failure within just 2-3 days, so rapid relief of the blockage is critical.
  • Struvite (magnesium ammonium phosphate) crystals are often present in the urethral plug and while these do not cause the obstruction, they may contribute to it.
  • Treatment: Usually the plug must be removed under anaesthetic, as the procedure may be painful for the cat. After the blockage is relieved, there can be quite severe inflammation of the urethra. This may cause swelling and spasms of the urethral muscles.
  • Some cats may need to be hospitalised for a period of time to monitor their progress. Cats will also need intravenous fluid therapy, and some may need a urinary catheter placed for a few days. If your cat is diagnosed with FLUTD, then we must place an IV catheter (sedate the cat to be able to place urinary catheter), monitor the urine output every 2-4 hours (when the obstruction is relieved) and match the IV fluid rate. This is necessary because we need to monitor and reestablish hydration levels.
  • Drugs to relieve pain, swelling and spasm are important.

Other causes of urethral obstruction include: small bladder stones becoming lodged in the urethra or severe muscle spasm of the urethra (which can occur with severe inflammation/irritation).

4.Anatomical defects

  • A stricture affecting the urethra.
  • This can be caused if the urethra becomes damaged, during the healing process. The fibrous tissue may develop as a scar tissue, which can significantly restrict the diameter of the urethra.
  • If this happens, it can be difficult for cats to pass urine normally.
  • Treatment: if a urethral stricture occurs, this can be difficult to manage, as surgery is usually needed to correct the problem. FIC is more complex, as the underlying causes are not fully understood.


  • The most common bladder tumour is known as “Transitional cell carcinoma” and occurs mainly in older cats. Surgical removal of the tumour is rarely possible.

6.Idiopathic cystitis

  • If no specific underlying disease can be identified, these cats are classified as having “feline idiopathic cystitis”. This term means that there is an inflammation of the bladder that has no known cause.
  • Others: Endocrine diseases such as hyperthyroidism and diabetes mellitus can cause lower urinary tract problems in cats.

References: https://pets.webmd.com/ https://www.avma.org/ https://icatcare.org/ Book: Clinical Medicine of the Dog and Cat: Second Edition ‐ by Michael Schaer, HILL’S ATLAS OF VETERINARY CLINICAL ANATOMY

It is important for all pet parents to have a basic understanding of common veterinary medical emergencies!

A blocked urethra in a cat can cause acute kidney failure within just 2-3 days, so rapid relief of the blockage is critical.

Be aware of Feline Lower Urinary Tract Disease (FLUTD)!

2 thoughts on “Feline Lower Urinary Tract Disease

Leave a Reply

Your email address will not be published. Required fields are marked *