At a glance
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). Pet owners often mistake the symptoms for constipation. However, a blockage is far more severe.
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 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.
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 an obstruction than females due to their longer and thinner urethra, which is the tube connecting the bladder to the genitals.
Crystalluria: Microscopic urinary crystals 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.
Cystitis: Inflammation or infection of the bladder can lead to a feeling of urgency to urinate. Cystitis is far more common in females than in males.
Bladder stones: Also called calculi or uroliths, bladder stones are rock-like substances formed in the bladder. They are the result of urinary crystals which clump together to form larger stones.
Bladder cancer: Bladder cancers are rare in cats; the tumour can potentially cause a blockage of the urinary tract.
Matrix plug: 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: Bleeding within the urinary tract has the potential to cause a urinary blockage in the urethra. Other predisposing factors include 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. Struvite is the most common type of crystal; calcium oxalate is the second most common type.
Struvite crystals can form in alkaline urine, so cat food manufacturers tried to combat this by lowering magnesium to make the urine more acidic, which lead to an increase in oxalate crystals. Other types of crystals include cystine, ammonium biurite, and bilirubin.
|Struvite crystals||Magnesium, ammonium, phosphate||Alkaline urine|
|Oxalate crystals||Calcium oxalate||Acidic urine|
|Urate crystals||Calcium urate||Acidic urine|
- Frequent visits to the litter tray
- Passing small amounts of urine, which may contain blood
- 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 can 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)
- Excessive thirst
Once the bladder becomes full, the kidneys can no longer remove wastes from the blood, resulting in toxins building up in the blood, which can quickly affect organ systems.
Your veterinarian will perform a complete physical examination of your cat including palpitating the abdomen where he will feel a firm, full bladder.
- Biochemical profile: This tests the clear portion of the blood to evaluate organ function.
- Urinalysis: A sample of urine is obtained to look for crystals in the urine, tumour cells and signs of infection.
- Urine culture and sensitivity: A small sample of urine is smeared on a growth medium that is cultured identify the type of bacteria present in the urine. Several antibiotics are placed on the medium to determine which is effective to treat the infection.
- X-ray or ultrasound: To look for the presence of stones or crystals in the bladder and assess urinary bladder size and wall thickness.
- Microscopic examination of stones or crystals: This helps the veterinarian determine what kind they are.
Intravenous pyelogram (IVP/excretory urography): A contrast medium (dye) is injected into a vein that the kidneys excrete via the urine which enables the technician to view the structures of the urinary tract, this can reveal small or radiolucent (transparent to x-ray) stones.
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 which allows urine to drain out of the bladder.
- Finding the cause of the blockage, which is usually due to crystals or stones, and treat accordingly, which may include 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 encouraging more water consumption.
- Administer fluids to correct metabolic and electrolyte imbalances. Your cat will receive fluids over several days to flush out the toxins via the urine (diuresis).
- Antibiotics to treat bacterial infections.
- Surgery to remove bladder stones or tumours.
- Antispasmodic medications, to relax the urethra.
- It may be necessary to perform a urethrostomy to increase the size of the urethral opening if the cat continues to block.
Be aware that once your cat has had a blockage once, he is at higher risk of developing another one. Especially as scar tissue can develop along the urethra, narrowing it further.
Increase water consumption: 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.
Avoid stress: Stressful situations can also result in a recurrence of a urethral blockage 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.