Bladder problems in cats: cystitis, crystals and blockage

FLUTD (feline lower urinary tract disease) is an umbrella term for signs that come from the bladder or the urethra, the tube that carries urine out. It is not one disease and not a diagnosis; the newest guidelines prefer the plainer term lower urinary tract disease because the name says nothing about the cause. It is common: it is one of the most frequent reasons a cat goes to the vet, and roughly 1 to 3 in 100 cats are affected each year, with middle-aged cats most often.

The usual causes are idiopathic cystitis (painful bladder inflammation without a known cause and without infection), crystals and stones, and plugs in the urethra. A bacterial infection is a less common cause. Rarely it is a tumour or a birth defect. 'Idiopathic' means the cause is not known. Idiopathic cystitis is the most common finding, in roughly 55 to 70 in 100 cats with these signs, and it is found by ruling other causes out, because no single test confirms it.

The word cystitis suggests an infection, as it does in people. In cats it usually is not one: the urine is usually sterile. Many cats have repeat episodes. Signs often settle in about a week, but they can come back, so a plan matters more than a single treatment.

The classic signs are straining or crying out while peeing, going to the box again and again for small amounts, blood in the urine, and peeing outside the box. Other signs are licking the genital area a lot, over-grooming the belly or back legs, restlessness, hiding, lying on cold floors or tiles, peeing in the bath or sink, a different smell, and changes in behaviour such as irritability.

Blood in the urine is not always visible. It can look red, pink or brownish, or only show on a vet's test. A healthy cat usually pees a few times a day. Many visits an hour with hardly any urine is a warning sign.

Straining in the box can look like constipation. The difference is the urine: if no urine or only drops come out, treat it as a possible blockage. Signs that come and go are easy to miss. In a study of young pet cats, owners reported crying out or blood in the urine, and the signs often came and went. If you notice them even once, mention them to the vet.

In a blockage the urethra is closed by a plug, a small stone, a blood clot or a spasm, so the bladder fills and the cat cannot pee. It happens almost only in male cats, because their urethra is longer and narrower. A blocked cat strains with little or nothing coming out, may cry, lick his penis, hide, vomit, stop eating and grow quiet and weak. A full, firm bladder may be felt at the back of the belly, but a bladder that cannot be felt does not rule a blockage out.

Without treatment a complete blockage can be fatal, because the kidneys fail and the potassium in the blood rises, which affects the heart. Sources say this can happen within about a day or two, so treat it as an emergency from the first moment. With quick treatment the outlook is good. Most blocked cats survive, although blockages come back in a share of cats.

Both sexes can have bladder problems, but most cases are not blockages. A vet has to find out which one it is.

Idiopathic cystitis (FIC) is thought to involve the nerves, stress hormones and the protective lining of the bladder, not only the bladder itself. Stress is believed to play a major part, and episodes often follow a change: a move, a new pet or baby, a conflict with another cat, boarding, or a change of food.

Crystals and stones are the cause of roughly 10 to 25 in 100 cases. The two common stone types are struvite and calcium oxalate. Struvite forms more easily in concentrated, alkaline urine and can often be dissolved with a vet-prescribed diet; calcium oxalate stones cannot be dissolved and usually have to be removed. Crystals alone are not a disease. Many healthy cats have crystals in the urine and never get stones or a blockage. A special diet is not needed for crystals alone, unless the cat already forms stones.

A urethral plug is mostly a mix of protein, inflamed cells and mucus, often with crystals. During a severe attack the bladder lining leaks protein that can build such a plug, which is how an inflammation can lead to a blockage.

A bacterial infection is an uncommon cause in healthy younger adult cats, under about 5 in 100. It becomes more likely in cats over 10, in females, and in cats with kidney disease, diabetes or an overactive thyroid, or after a catheter or urinary surgery. Other causes are uncommon: a bladder tumour, mostly in much older cats, a birth defect, nerve damage, or an injury.

Risk goes up in middle-aged cats, overweight cats, cats that move little and spend all their time indoors, cats that mainly eat dry food and drink little, and cats living with other cats. Neutered males are most at risk of blockage because of the narrow, long urethra. Females are not immune: they can get cystitis, stones and, especially when older, infections.

Studies point to a nervous or fearful temperament and a stressful environment. The most common stress trigger in cats with FIC is conflict with another cat in the home, and having fewer litter boxes than cats is also linked to it. Not every study agrees. A study of young pet cats found indoor life linked with owner-reported signs, but no clear link with body condition, dry food or neutering, so the risk factors are tendencies, not rules. Persian cats may be more prone to bladder problems, but this is a single mention and the evidence is weak.

The vet asks about the home, the diet and the litter boxes, examines the cat and feels the bladder, and tests the urine for concentration, acidity, blood, crystals, cells and bacteria. If the cause is unclear or the problem returns, the next steps can be a urine culture, blood tests, X-rays or an ultrasound scan. X-rays show small stones in the lower urethra that ultrasound cannot reach. Older cats, cats with leaking urine and cats whose signs return get a fuller check, including imaging.

For a culture the vet often takes urine straight from the bladder with a fine needle, which gives a clean sample. Urine should reach the vet fresh, because old or refrigerated urine can show crystals that were not there. You can often collect a sample at home with a non-absorbent litter that the clinic gives you. Do not press on the bladder to get urine out: it hurts and can damage the bladder wall.

Idiopathic cystitis has no cure and no single proven medicine. Care rests on pain relief, more water and a calmer home; the home changes are called multimodal environmental modification (MEMO). Medicines are chosen by the vet and are used only when diet and home changes have not been enough. Antibiotics are not a treatment for idiopathic cystitis. Vets use them when a urine test shows a bacterial infection, ideally after a culture. Giving them without a test is not useful for most cats and adds to unnecessary antibiotic use.

Painkillers are a cornerstone, but only a vet should choose them: some pain medicines harm the kidneys of a dehydrated cat, and many human medicines are toxic to cats. Other measures for repeat or severe cases include a vet-prescribed diet, anti-anxiety medicine for cats that stay stressed, and a referral to a behaviour specialist. Steroids and bladder-lining supplements showed no clear benefit in studies, and evidence for supplements such as cranberry is weak.

Struvite stones can often be dissolved by a prescription diet over a few weeks, with repeat imaging to check. Calcium oxalate stones cannot be dissolved and are removed by surgery or other methods; the stone is sent to a laboratory to find its type.

A blocked cat is treated in the clinic: pain relief, a drip, treatment of dangerous potassium levels, and a soft urinary catheter passed under sedation or anaesthesia to empty the bladder. The catheter may stay a few days, and stays in hospital last from days to weeks. A large 2022 study of 388 male cats found that prazosin, a muscle-relaxing medicine vets sometimes give to prevent a repeat blockage, did not lower the chance of another blockage and was linked to more early re-blocking. Medicines for this are for the vet to choose. For a male cat that blocks again and again, or whose blockage cannot be cleared, a last-resort surgery called perineal urethrostomy widens the urethra. It lowers the chance of re-blocking but has risks such as bleeding for a few days, narrowing and incontinence.

Costs depend on the cause. A check with a urine test costs far less than a stay for a blockage or an operation, and prices differ per practice, so ask for an estimate.

Water is the most important nutritional factor for every cause: diluted urine is less irritating and flushes out crystals. Wet food adds a lot of water and is the only nutrition step linked to fewer FIC signs in controlled studies. If your cat eats dry food, change slowly and never starve a cat onto a new food. Some vets advise wet food only, others add wet food to dry; discuss which fits your cat.

Prescription urinary diets exist for cats with stones and some with FIC. They suit one purpose each, so they are only for use on a vet's advice, and not every cat benefits. Do not mix different urinary foods or add urine acidifiers on your own, because over-acidifying can harm the kidneys. A urinary diet does not stop all bladder problems. It may lower the chance of a blockage, but there is no evidence that it prevents every episode. Do not change a cat's food during an episode. Wait until the cat is eating well, and then change gradually.

Offer water in several places, away from noise and from the litter box. Wide ceramic bowls, a drinking fountain and a dripping tap help some cats drink more. Keep bowls from touching the whiskers. Add wet food to the daily ration, or moisten dry food, and give small meals often at steady times.

Provide one litter box per cat plus one extra, in quiet places spread around the home, scooped daily and washed weekly with warm water. Use a large box, about one and a half times the length of the cat, with an unscented litter the cat likes.

Reduce stress: keep a steady routine, give hiding places, high resting places, scratching posts and daily play, give each cat in a multi-cat home its own food, water and rest spots, and make changes at home one or two at a time. A plug-in synthetic pheromone diffuser may help some cats, but the evidence is mixed. Keep a healthy weight and let the cat move and play. Overweight, inactive cats get bladder problems more often. After a first blockage, the risk of blocking again is highest in the first week, so watch urine output closely and keep to the vet's plan.

Peeing outside the box is both a sign of bladder pain and a common behaviour problem. A sudden change usually points to a medical cause, while a gradual change after a stressful event points more to behaviour. Rule out a medical cause first. Cats in pain may choose soft surfaces or cold tiles, and peeing outside the box can be the first thing an owner notices.

Never punish a cat for it: it adds stress and does not fix the cause. Clean old spots with an enzyme cleaner, because ordinary cleaners hide the smell from people while the cat still smells it.

Most cats with idiopathic cystitis live a fairly normal life with changes to water, food and the home, and the condition often eases with age. A minority are hard to keep comfortable and may need a specialist or a behaviour expert.

Repeat episodes are common. In studies up to about half or more of cats with FIC had another episode within one or two years, which is why prevention matters.