Urinary blockage in male cats: the emergency that cannot wait
This is probably the most important emergency for anyone living with a male cat to know about. It gets mistaken for constipation or "he is acting oddly", and within 24 to 72 hours it can be fatal. Treated properly and in time, almost all cats pull through.
What is happening
The male cat's urethra, the tube that carries urine out of the bladder, is long and very narrow at its end, in the penis. All it takes is a small plug of crystals, mucus and inflammatory cells, a tiny stone or a spasm caused by inflammation for it to close. The bladder keeps filling but cannot empty, it stretches and becomes extremely painful. And the worst happens inside: unable to get rid of urine, potassium and other substances build up in the blood, and high potassium disrupts the heart rhythm. A blocked cat can die of cardiac arrest or kidney failure in one to three days. Females, with a shorter, wider urethra, rarely block; males, neutered or not, do.
The signs you need to recognise
The cat goes in and out of the litter tray again and again, gets into position to urinate and strains, but nothing comes out or only a few drops, sometimes with blood. He may cry or complain as he tries, lick his genitals a lot, pass small amounts of urine outside the tray or seek out cool places such as the bath or the sink. Later he stops eating, vomits, hides, is very flat, weak or wobbly, and his belly hurts when touched. Many owners think he is constipated because they see him straining in the tray: in a male cat, any straining in the litter tray without a clear result must be treated as a possible blockage until the vet says otherwise.
What to do: go now
Do not wait until tomorrow or to see whether he passes urine overnight. Call your clinic or a 24-hour emergency clinic, tell them you are bringing a male cat who cannot urinate, and set off. Carry him in his carrier gently, without squeezing his belly. Do not try to empty his bladder by pressing on it: you could rupture it. Do not give anything for pain or to help him urinate on your own, least of all human medicines; paracetamol is deadly to cats. If you are not sure whether he is urinating, look at the litter: are there normal-sized clumps from the last few hours? If there are only tiny spots or nothing, go. An emergency visit for nothing is better than arriving too late.
What the vet will do
First, stabilise him: urgent blood tests to check potassium and kidney function, an ECG if needed, intravenous fluids and pain relief. Then, under sedation or anaesthesia, the vet will pass a urinary catheter up the urethra to clear the plug and empty the bladder, and will often leave it in place for one to three days while the cat is hospitalised, so the urethra can settle and the kidneys can recover. The urine will be tested for crystals, infection or blood, and X-rays or ultrasound are often done to look for stones. When the catheter comes out, the vet checks that the cat is urinating well on his own before sending him home with painkillers, sometimes urethral relaxants, and the recommended diet.
What it costs
It is an expensive emergency, and it is worth knowing beforehand. As a guide in Spain in 2026, unblocking with catheterisation, blood tests and two to four days in hospital usually costs between 600 and 1,500 €, and can exceed 2,000 € if there are complications, if it has to be repeated or if it is done out of hours at a big-city emergency clinic. If the cat blocks repeatedly, perineal urethrostomy surgery, which widens the urinary outlet, costs 1,000 to 2,500 €. Pet insurance with emergency cover or a reserve fund for the cat means you do not have to decide with your wallet in a situation like this.
Why it happens
The most common causes are urethral plugs, made of proteins, inflammatory cells and often struvite crystals, almost always in the context of feline idiopathic cystitis, a bladder inflammation closely linked to stress. Next come small stones, struvite or calcium oxalate, and urethral spasm caused by the inflammation itself. These conditions are grouped under the term FLUTD (feline lower urinary tract disease). The well-known risk factors are being male, being overweight, being inactive, living alone indoors with little stimulation, drinking little and eating only dry food, and stress: changes at home, conflict with other cats, too few or dirty litter trays.
Relapse: the risk in the following weeks
A cat that has blocked once has a fair chance of doing so again, especially in the first days and weeks. After discharge, check the litter tray every day: size and number of clumps, straining, blood. If he starts going in and out without urinating again, go back to the clinic without waiting. Stick to the medication, diet and check-ups, even if he seems fine. If blockages keep recurring despite everything, perineal urethrostomy is an operation with good results that greatly reduces the risk of further blockages, although it does not get rid of the underlying cystitis and can make urinary infections more likely.
Prevention: water, weight and less stress
What works best is increasing water intake: wet food as the base of the diet, or at least a large part of it, added water, several water bowls, fountains. If the vet recommends it, a therapeutic urinary diet, which can dissolve struvite crystals and reduce their formation; be careful, because not every supermarket "urinary" food is therapeutic, and some are no use for oxalate. Keep him at his ideal weight and play every day. And reduce stress: one litter tray per cat plus one, cleaned daily, in quiet places; separate food bowls, water bowls and resting areas in multi-cat homes; hiding places and high spots; stable routines. All of this, which looks like interior design, is treatment.
Which cats need more attention
Young and middle-aged males, roughly between one and ten years old, overweight, indoor, eating mostly dry food and living in homes with some source of stress, such as several cats, building work, house moves or changes in routine. If your cat ticks several of these boxes, do not panic, but learn the signs and check the litter tray every day. Being neutered neither protects nor dooms a cat: what matters is his weight, hydration and environment. And although blockage is far rarer in females, a female cat that strains often and passes bloody urine also needs a vet, although not usually with the same urgency.
A male cat who goes in and out of the litter tray without passing urine, or only a few drops, is an emergency: he can die in one to three days because of potassium. It is not constipation or a whim. Go to the clinic now, and afterwards prevent it with water, a healthy weight, clean litter trays and less stress.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.