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Cat Straining to Urinate

What causes urinary blockages?   Types of urinary crystal   Symptoms of a urinary blockage  Diagnosing a urinary blockage   Treatment for a urinary blockage   Preventing urinary blockages

urinary blockage in cats

Have you noticed your cat going to the litter box more often than usual? Is he digging around in the litter tray, crying, straining, licking his genitals? You may have a cat with either a partial or a full urinary blockage (medically known as ischuria). If he is urinating, you may notice the urine is pink, which means it contains blood (hematuria). These symptoms are often mistaken for constipation, but a blockage is far more serious.

Please do not delay taking your cat to a veterinarian as a urinary blockage can quickly lead to death. Even if you are not sure if your cat is constipated, a medical evaluation is absolutely vital at this time.  If your cat can't urinate, waste products quickly build up in his bloodstream leading to uremic poisoning, which is life threatening.

What causes urinary blockages?

The cause may be urinary crystals, bladder stones and bladder tumours, which may extend to the urethra, causing a blockage. Males are more at risk of a blockage than females due to their longer and thinner urethra, which is the tube connecting the bladder to the genitals.

  • Microscopic urinary crystals (crystalluria) can develop if the urine becomes too concentrated. Over time small crystals form in the urine. It has been speculated that the trend in feeding a diet made up of predominantly dry food is contributing to the problem.  Many cats aren't big water drinkers, in the wild, they would obtain a larger amount of moisture through their prey (the average animal is made up of around 70% water), however dry food only contains 10% water and many cats don't make up this shortfall, leading to the urine becoming supersaturated. Urinary stones are made up of struvite, oxalate or urate.
  • Another common cause is cystitis, which is inflammation or infection of the bladder. This can lead to a feeling of urgency to urinate.  Cystitis is more commonly seen in females than males. 
  • Bladder stones (also known as calculi or uroliths) are rock-like substances formed in the bladder. They are the result of urinary crystals (mentioned above) clumping together to form larger stones.
  • Bladder cancers are rare in cats, the tumour can potentially cause a blockage of the urinary tract.
  • If crystals are present along with inflammation, a matrix or urethral plug can potentially form, this is comprised of inflammatory cells, crystals, urinary tract cells and mucoid material. Combined, this matrix forms a plug, blocking the urethra.
  • Hypercalcemia (high blood calcium levels) can cause increased calcium levels in the urine, leading to the formation of calcium oxalate crystals.
  • Blood clots are the result of bleeding within the urinary tract and have the potential to cause a urinary blockage in the urethra.

Other predisposing factors to the formation of urinary crystals includes a multiple cat household with shared litter trays, especially when there aren't enough, or they're not cleaned as often as required. Obesity and stress also play a role.

Types of crystals in cat urine:

Crystals are more likely to form in either acidic or alkaline urine. The most common type of crystal seen in cats is struvite followed by calcium oxalate.

Struvite crystals can form in alkaline urine, so cat food manufacturers tried to combat this by lowering magnesium. This made urine more acidic, which lead to an increase in oxalate crystals. Other less common types of crystals include cystine, ammonium biurite (which is associated with liver shunt), and bilirubin.

Type Composition Cause
Struvite crystals Magnesium, ammonium, phosphate Alkaline urine
Oxalate crystals Calcium oxalate Acidic urine
Urate crystals Calcium urate Acidic urine

What are the common symptoms of a cat who can't urinate?

  • Frequent visits to the litter tray
  • Passing small amounts of urine, which may be blood tinged
  • Crying when in the litter tray
  • Pain in the abdomen, discomfort when touched or sitting hunched over
  • Abdominal swelling
  • Licking the genitals
  • Urinating (if he is able to pass any) outside the litter tray
  • Lethargy (a friend who lost a cat to a urinary blockage initially thought his cat had been bitten by a paralysis tick)
  • Vomiting
  • Excessive thirst

Once the bladder becomes full, the kidneys can no longer remove wastes from the blood, resulting in them building up in the blood, this can quickly affect organ systems. If immediate medical treatment to reverse the blockage isn't carried out your cat can quickly collapse and fall into a coma, eventually dying.

How is a urinary blockage diagnosed?

Your veterinarian will perform a complete physical examination of your cat including palpitating the abdomen where he will feel a firm, full bladder. Other tests he may want to perform include:

  • Biochemical profile to evaluate organ function.
  • Urinalysis to look for crystals in the urine, tumour cells and/or signs of infection.
  • Urine culture and sensitivity to identify the type of bacteria present in the urine if infection is present.
  • X-ray or ultrasound to look for the presence of stones or crystals in the bladder and assess urinary bladder size and wall thickness.
  • Evaluation of stones or crystals to determine what kind they are. This can help  your veterinarian tailor the treatment plan.
  • Intravenous Pyelogram (IVP/excretory urography): To see very small or radiolucent (transparent to x-ray) stones may require contrast radiography. This is where a contrast medium (dye) is injected into a vein. It is excreted via the kidneys and appears in the urine. This enables the technician to view the structures of the urinary tract. - See more at: http://www.cat-world.com.au/Cat-Health-Collection/bladder-stones-in-cats.html#sthash.JJOB5Abh.dpuf

How is a urinary blockage treated?

Treatment depends on the severity of the blockage. Your veterinarian may be able to manually express the bladder by palpitating the urethra. If this is not possible, he will insert a catheter (a thin tube) via the penis/urethra or urethra in females and into the bladder. This allows urine to drain out of the bladder.

  • Finding the cause of the blockage, which is usually due to crystals or stones, and then treating accordingly. This is generally managed by putting the cat on a prescription diet to dissolve the stones and change the pH of the urine.
  • Increasing water consumption by switching him to a wet food diet and/or encouraging more water consumption.
  • Fluids may be administered to correct metabolic and electrolyte imbalances. As toxins will have undoubtedly built up in the cat's blood, fluids may be given over a period of several days to flush these out of the system by increasing urination. This is known as diuresis.
  • Antibiotics will be prescribed to treat bacterial infections.
  • If your cat has bladder stones, surgery will be necessary to remove the stones. This may be followed up with chemotherapy.
  • Antispasmodic medications may be prescribed, to relax the urethra.
  • If your male cat continues to block, urethrostomy surgery may be required to increase the size of the urethral opening.
  • If you live in a multi-cat household and/or have a stressed cat, I recommend using Feliway. This product is made from a synthetic hormone which mimics the cat's own 'feel good' hormone. This can help reduce stress in your cat.

How is it avoided in future?

For crystals and bladder stones, changing your cat's diet to include more wet foods is important. The more moisture, the more dilute the urine will be.

Be aware that once your cat has had a blockage once, he is at greater risk of developing another one. Particularly as it is possible for scar tissue to develop along the urethra, narrowing it further.

Stressful situations can also result in a recurrence of a urethral blockage. This is because a stressed cat will often hold onto his urine for longer than he should, once again, resulting in supersaturated urine which is the perfect environment for crystals to develop.

Related content:

Causes of litter tray refusal

Last updated 28th August, 2016.