Urethral obstruction in males

Read this section twice. It is the one emergency in this course where hours matter, and it is the one owners most often get wrong, because from across the room a blocked cat looks like a constipated cat.

The short version. A male cat that keeps straining and produces nothing, or only drops, is a blocked cat until a vet says otherwise. That is an emergency within hours. Go now, whatever the time of night.

What it is

A blockage means the urethra, the tube from the bladder to the outside, is plugged so that urine cannot leave. It occurs almost exclusively in male cats and is the life-threatening complication of lower urinary tract disease.³ The reason is plumbing: a male cat's urethra is longer and narrower than a female's, so it blocks more readily.¹⁴²⁷ Neutering does not change this. Obstruction is more common in younger, overweight and male cats, with no difference between intact and neutered males.²

Any urinary disease can end in a blockage, and idiopathic cystitis is the most commonly reported cause.³

What you'll see

The commonest presenting sign is straining in the litter box with nothing coming out, sometimes with crying.³ Owners commonly mistake this for constipation, and the mistake costs the hours that matter.³²⁸ So we will say it plainly: if your male cat is straining and you think he is constipated, treat him as blocked until a vet has checked, because the two look the same from the doorway and only one of them kills.

Before the blockage is complete you may see the ordinary urinary signs: frequent small pees, peeing outside the box, blood in the urine.³ Once a blockage has lasted more than 24 hours the cat becomes ill all over: vomiting, not eating, lethargy, seeming not quite present, weakness and stupor.³ A cat with a severe, prolonged blockage may be found collapsed on his side.³ His bladder is typically hard, swollen and painful, which you may notice as a tense belly he will not let you touch.³²⁸ Urethral obstruction is a true medical emergency, and any cat suspected of it needs a vet immediately.¹⁴²⁸

Do not give a straining cat any human painkiller while you wait or on the way. Acetaminophen (paracetamol) and ibuprofen are among the commonest causes of poisoning in cats, and both can kill.

What the vet will do

When urine cannot leave, waste products build up, and the resulting disturbances include high blood potassium, acid build-up and low blood calcium.³ High potassium is the most common life-threatening complication, because it slows the heart and causes rhythm problems.³

In outline, the vet checks the cat for shock and high potassium, starts intravenous fluids, gives pain relief, and then relieves the blockage with a urinary catheter under sedation or anaesthesia.³¹⁴²⁸ Pain relief is a priority in its own right, and in some cats controlling pain relaxes the urethra enough that they start to pee on their own.³ The catheter usually stays in for no more than about 24 to 36 hours unless the cat's blood values have not come right.³ X-rays find an underlying cause in 30 to 40% of blocked cats and are the first imaging test of choice.³

Survival to discharge after standard treatment is excellent, at 91 to 94%.³⁸ The longer view is less rosy: the same studies report re-blocking rates of 11 to 58% at various time points, with 21% of cats eventually put to sleep.³⁸ Treating a blocked cat as an inpatient with a catheter and fluids cut re-blocking within 30 days compared with a single catheterisation and discharge, 11% against 31%.⁸

Your vet may prescribe a drug intended to relax the urethra after the catheter comes out; prazosin is the usual one, and it is widely used. On current evidence the 2025 consensus does not generally recommend prazosin.³ This is a live disagreement among vets, and it is their call, not yours.

A bladder that has been stretched can stop contracting, so a cat may fail to pee even though the urethra is now open, and recovery can take 7 days or longer.³

For a cat that keeps blocking, or where money limits further medical care, a surgery called perineal urethrostomy widens the urethral opening, with a good reported outlook for blockages near the tip.³ Surgery does not cure the underlying disease: the bladder problem, usually idiopathic cystitis, still has to be managed afterwards.³

Cost is the thing nobody prints. The only published comparison we have is from a 2010 US teaching hospital, where standard treatment was estimated at $1,200 to $1,800 against a set $350 for a low-cost alternative; those are 2010 US dollars, and Alberta prices today will differ.³¹ That cheaper protocol succeeded in 11 of 15 cats, but its own authors said it cannot be recommended as an alternative to conventional treatment, because the two were never compared directly.³¹ The honest framing is that a cheaper protocol exists as an alternative to euthanasia, not as an equivalent to proper treatment.⁸³¹ Our own suggestion, and it is only ours: ask your clinic what a blockage costs and what payment options exist before you ever need to know.

What you can do at home

Preventing the next blockage is the same work as preventing the next bout of the underlying disease: environmental changes, water, enough boxes and the right diet.³ When your cat comes home, you need a workable plan for ongoing pain relief and advice on reintroducing him to the other cats, because he will smell of the hospital.³