There are several reasons why a cat may have difficulty urinating or may stop producing urine altogether. The most common causes are:
1. Urethral obstruction
This is the most frequent cause, especially in male cats.
- Bladder inflammation (FIC – Feline Idiopathic Cystitis)
Inflammation of the bladder wall can make urination painful or cause the cat to pass only small amounts of urine. In severe cases, the urethra can go into spasm and become completely blocked. This is seen more often in male cats. Because their urethra is narrow, inflammatory cells can get stuck together with bladder crystals and debris from the diet. This forms a “plug,” similar to putty, which then blocks the urethra.
- Bladder stones
Stones form in the bladder when crystals excreted by the kidneys clump together. Larger stones can block the bladder outlet or become lodged in the urethra. This happens more often in male cats than in females. Male cats have a natural narrowing of the urethra at the level of the penis, making this the most common place for stones to get stuck.
Cats are experts at hiding illness, so stones may have been present for some time without you noticing. The most common types of stones in cats are struvite and calcium oxalate (see “Struvite in cats” or “Calcium oxalate in cats”).
2. Urethral spasm
Pain, stress or inflammation can cause the urethra to spasm so tightly that urine can no longer pass. This can also occur after a temporary urinary catheter has been placed. Treatment may include medication such as diazepam (see “Urological medications”) or placing a soft silicone urinary catheter that is removed once the medication has taken effect.
3. Less common causes
Occasionally, another underlying reason may be found. These are less frequent:
-
Tumors: Tumors of the bladder or urethra are uncommon in both male and female cats. They usually cause increased urgency rather than complete inability to urinate. Diagnosis is made with ultrasound of the urinary tract, sometimes combined with endoscopy.
-
Trauma: Injury to the pelvis (for example, after a car accident) can damage the urethra or the nerves that control urination. The bladder may feel very firm, and the sphincter may be excessively tight.
-
Neurological problems: Issues affecting the spine or brain (such as nerve disorders, dementia, parasites or tumors) can disrupt the normal control of the urinary system, leading to various urination problems.