More precisely, urine outflow through the urethra is blocked. Urine accumulates in the bladder because it cannot leave the body normally. Even a suspected blockage is an emergency.
When to see a vet urgently
Go to an emergency vet immediately if you notice any of the following:
- Your cat strains to urinate but passes no urine or only drops.
- Repeated litter tray visits involve pain, restlessness or crying out.
- Difficulty urinating is accompanied by vomiting, failure to eat or marked lethargy.
- Your cat cannot stay on its feet, collapses or responds poorly.
Contact the clinic and transport your cat without delay. You can find an emergency vet near you. Do not wait for every symptom to appear.
Overview
Urethral obstruction can develop suddenly, often alongside feline lower urinary tract disease (FLUTD). The blockage may consist of mucus or protein plugs, crystals, stones or swelling of the urethral wall. When urination is prevented, the bladder fills rapidly, causing severe pain, impaired kidney function and electrolyte disturbances. Without treatment, the cat may die within 24–72 hours.
The number of hours stated is not a safe waiting period: the condition can deteriorate rapidly and life-threatening changes can develop sooner. You also usually cannot know when a complete blockage began. Treatment needs are determined by difficulty urinating, rather than by counting hours.
Lower urinary tract signs are an umbrella term covering several diseases. Pain, blood in the urine and frequent litter tray visits do not identify the cause on their own. In idiopathic cystitis, bladder inflammation without another identified cause, the stress response system and environment can have significant effects. Inflammation therefore does not always mean bacterial infection.
Causes
The main causes of urethral obstruction in male cats include:
- Crystals and stones, such as struvite and oxalate.
- Mucus or protein plugs.
- Swelling of the urethral lining associated with cystitis.
- Tumours of the urethra or bladder.
- Urethral spasm due to pain and inflammation.
Both a mechanical blockage and functional contraction of the urethra can contribute to the same clinical picture. Bladder inflammation, a plug and a stone are not the same diagnosis, although all can lead to difficulty urinating. After treatment, the cause of the blockage is investigated where possible.
Not all urinary stones are alike. Some can be dissolved with a diet chosen for that purpose, but not every stone type responds. Emergency treatment for a blocked cat cannot be replaced by a dietary trial, as dissolution does not happen quickly enough to relieve an acute obstruction.
Risk factors
Urethral obstruction occurs more often in cats that:
- are neutered
- are overweight
- are inactive
- eat dry food and take in little water
- live in stressful environments, such as multi-cat homes or during house moves
Neutering does not itself narrow a cat's urethra. The list should therefore not be interpreted as meaning a blockage is automatically caused by neutering. Weight, activity, water intake and living environment are assessed together. A particular feeding method alone also neither establishes nor rules out the cause of obstruction.
Main symptoms
A urethral blockage may be suspected from the following signs:
- frequent unsuccessful attempts to urinate
- pain and loud meowing during urination
- blood in the urine or no urine
- a firm, enlarged bladder on palpation
- apathy and lethargy
- vomiting and loss of appetite
- seizures, collapse and loss of consciousness in severe cases
Feeling the bladder is part of a veterinary examination. Do not try to squeeze the abdomen or empty the bladder by hand. With a partial or early blockage, the bladder may not yet be markedly enlarged, so failing to feel a lump at home does not rule out the problem.
Straining can be mistaken for constipation, and a cat may also lick its genital area or hide. Some cats are still fairly bright in the early stages. If you do not know whether your cat is trying to urinate or pass faeces, this is a reason for prompt assessment. A few drops of urine do not show that the bladder is emptying normally.
Complications and consequences
Without urgent treatment, urethral obstruction leads to:
- bladder rupture
- severe electrolyte disturbances, including hyperkalaemia
- kidney failure
- toxic effects within the body
- death
Hyperkalaemia means an excessively high potassium level in the blood. It can disrupt the heart's electrical activity and cause serious arrhythmias. Initial treatment of a very ill cat may therefore need to support circulation and correct potassium disturbances while preparations are made to relieve the blockage.
Rising pressure and blocked urine outflow also impair the kidneys' ability to regulate body fluids and remove waste products. Lethargy and vomiting can therefore reflect a wider problem than local bladder symptoms. Severity cannot be determined from urine colour alone or how loudly a cat expresses pain.
Diagnosis at the vet
Your vet carries out:
- bladder palpation
- urethral catheterisation to confirm and relieve obstruction
- a complete blood count and biochemistry to assess kidney function and electrolytes
- urine analysis
- ultrasound or X-rays to detect stones
As well as the bladder, clinical examination assesses general condition, hydration and circulation. An electrocardiogram, or ECG, helps detect arrhythmias. Blood tests focus particularly on potassium, kidney values and, where necessary, acid–base balance. The order of investigations is tailored to your cat's condition so that treatment of a seriously ill cat is not delayed unnecessarily.
A urine sample is examined for inflammatory findings and crystals, among other things. Bacterial culture is performed as needed because similar urinary signs do not always mean bacterial infection. Crystal findings are considered alongside imaging and the overall assessment; they do not, by themselves, establish the presence or treatment of every possible stone.
X-rays and ultrasound can look for stones and bladder changes. Some stones do not appear on ordinary X-rays, in which case ultrasound or contrast imaging can add information. A catheter is a thin tube passed through the urethra into the bladder to relieve the blockage and allow urine to drain.
Emergency treatment and hospital monitoring
Treatment includes pain relief and, where necessary, intravenous fluids and correction of dangerous electrolyte changes. Removing the blockage usually requires sedation or general anaesthesia. A very unstable patient may first need stabilisation so the procedure can be carried out as safely as possible.
During catheterisation, the obstruction is relieved and the bladder may be flushed. The catheter may be left in place temporarily, allowing urine to drain and its volume to be monitored. General condition, kidney values and electrolytes are monitored as they recover. Any urinary stone or other underlying cause needs its own treatment plan.
After catheter removal, the team checks that your cat can urinate independently. Briefly opening the obstruction alone does not establish that discharge is safe. If urination becomes blocked again, treatment continues. Antibiotic needs are assessed according to confirmed or suspected bacterial infection, rather than inflammatory signs alone.
If the blockage cannot be relieved or recurs despite appropriate treatment, a perineal urethrostomy may be considered. Surgery creates a wider urethral opening by removing the narrow end section. It can reduce the risk of another blockage, but does not prevent all bladder inflammation or stone formation. Surgery also carries complication risks, so the need is assessed individually.
Home care and recognising recurrence
At discharge, ask for instructions on medication, feeding and what urination to expect. Monitor the amount of urine in the litter tray and whether urine is actually being passed. Mild irritation may occur after treatment, but renewed unsuccessful straining is not safe to monitor at home.
Contact the clinic immediately if no urine is passed, pain increases, your cat vomits or becomes subdued. In a multi-cat home, you must be able to distinguish the treated cat's urination from other cats' visits. Agreed follow-up and treatment of the underlying cause continue even if your cat seems recovered.
Prevention
Preventing urethral obstruction involves:
- following an appropriate diet, including special diets for cats that form crystals
- ensuring free access to drinking water
- weight management
- reducing stressors
- regular preventive checks for at-risk cats
- prompt treatment of cystitis and urinary stone disease
Diet is chosen according to investigation findings; not all urinary diseases are treated with the same food. Water intake can be encouraged by offering wet food and several appealing drinking places. Adding water to food is suitable only if your cat accepts the change and continues eating enough.
Provide clean, quiet litter trays and opportunities to rest and retreat. In a multi-cat home, make sure one cat does not block another's access to water or the tray. Play, climbing places, hiding spots and a predictable routine support activity and reduce stressful situations. Make changes at a pace your cat accepts.
What it means for owners
Urethral obstruction in a male cat is an emergency. Remember that a cat repeatedly sitting in the litter tray without results, crying loudly or showing pain must be taken to a vet immediately. Do not try home remedies: rapid treatment can save your cat's life.
This material is for information and does not replace veterinary advice. Seek veterinary attention immediately when the first signs of illness appear.
Frequently asked questions
Can a urinary blockage wait until morning?
No. Even suspicion is an emergency. The condition can deteriorate quickly, and you usually cannot know how long the blockage has really been present.
Do a few drops of urine rule out a blockage?
No. Dribbling does not guarantee normal bladder emptying. Repeated straining with little or no urine needs immediate examination.
Does neutering narrow the urethra?
No. Neutering should not be treated as the explanation for a narrow urethra. Weight, activity, water intake and other risk factors are considered separately.
Does surgery remove every urinary problem?
No. Urethrostomy can improve urine outflow and reduce blockages, but bladder inflammation or stone formation may continue. Feeding, environment and monitoring remain part of care after surgery too.
This article is for general information only and is not a guide to treatment. If you notice the first signs of illness, contact your vet.
Paw4care editorial team
Sources
- Feline Lower Urinary Tract Disease, Cornell Feline Health Centre, accessed 2026-11-03.
- Urinary Obstruction in Male Cats, American College of Veterinary Surgeons, accessed 2026-11-03.
- Urethral Obstruction in Small Animals, Merck Veterinary Manual, accessed 2026-11-03.
- Urethral Obstruction in Cats, MSPCA-Angell, accessed 2026-11-03.
- Feline Idiopathic Cystitis, VCA Animal Hospitals, accessed 2026-11-03.
- Basic Indoor Cat Needs, The Ohio State University, Indoor Pet Initiative, accessed 2026-11-03.
- Bladder Stones in Cats, VCA Animal Hospitals, accessed 2026-11-03.