When Your Cat Can’t Pee – Feline Urological Syndrome

aka FUS /Feline Lower Urinary Tract Disease (FLUTD)

Ron Hines DVM PhD

This problem – with many long and complicated names – is responsible for perhaps 5-10% of all cat office visits to their veterinarian. Owners often present those cat for a “litter box problem” – either too much time spent in the box or urination outside of the box

Both male and female cats suffer from FUS ; but it is only a life-threatening disease if your cat is a male.

FUS is a very perplexing disease of the bladder and urethra. Veterinarians and veterinary nutritionists do not understand why one cat develops this problem while another cat, under identical circumstances, or living in the same household does not.

In FUS/FLUTD, sharp crystals fall out of solution in your cat’s urine while it is still in the bladder. These crystals irritate the lining of the cat’s lower urinary tract. When they mix with debris, sloughed from the bladder lining, they can prevent your cat from urinating.

What Kinds Of Cats Get This Problem?

Cats of any age can develop lower urinary tract problems. But the average cat is about 4 years old when signs begin. It is very uncommon in cats under 1.5 years of age. Old cats can also develop FLUTD. But when they do, they usually have another, underlying health or stress problem. We see FLUTD a bit more frequently in Persian cats than in standard domestic cats.

Until the mid 1990s, these crystals were usually composed of the mineral, struvite (ammonium-magnesium-phosphate). But since then, the incidence of calcium oxalate crystals has mysteriously increased until, currently, they make up more than half the cases of FLUTD. The presence of these crystals is never fatal to female cats but it is life-threatening in male cats if it prevents their urination. I think of this disease as the “Garfield Syndrome” – because it appears to be a disease of easy living – it is most often a pampered indoor cat that develops the disease.

Much more about FUS/FLUTD still remains unknown than known.

What Signs Might I See In My Cat?

The first thing many owners notice is that their cat is spending too much time in it’s litter box.

A second common complain is that their pet is urinating outside the litter box.

You can read an article specifically about that problem here.

It can be hard to decide if your cat is straining to urinate or to poop. But it is usually obvious there is a problem with one or the other when they squat too long. If the consistency and color of their stool has not changed, suspect a urinary problem. Sometimes these cats will meow and show their discomfort while making their attempts. Between attempts, they often lick there genital area. There may be blood in its urine. Their penis may no longer be withdrawn entirely into its sheath and it may be bluish or inflamed at its tip. There may be a white, cheese-like material surrounding the penis and sheath.

These pets often begin to urine-spray in unusual locations in the house – particularly sinks, tubs and closets. It is not unusual for some sort of household change or stress to precede an attack.

What Is Going On In My Cat?

When FLUTD/FUS occurs, small sharp crystals form in the pet’s urine, irritating the bladder and urethra lining. Sometimes, but quite rarely, actual gravel-like stones form.

Because struvite crystals contain magnesium, one theory was that the problem occurred due to feeding cat foods high in mineral (ash). This seemed logical. The only problem was that no one was able to reproduce the disease by feeding high ash/magnesium diets to normal cats. Some contributors to pet food ash are necessary (calcium and trace minerals) – however, cheap cat foods are often higher in ash than they should be.

So other factors must be at work. Some speculated that bacteria or virus are involved. However, most cats with this problem have no bacteria or virus in their urinary tracts. When bacteria are found in voided urine, they are often no more than contaminants. However, when they are present in urine obtained through a needle (cystocentesis) they need to be dealt with.

Another thought was that lethargic, indoor cats do not drink enough water. We know that these crystals occur more frequently in concentrated urine. However, just as we could not cause the disease with high ash diets, producing concentrated urine didn’t cause the disease either.

Struvite appears when the pH (acidity) of your cat’s urine is greater than 7 and possibly also when dietary magnesium levels are high. When animal nutritionists realized this, they reformulated cat foods to produce more acid urine with a pH range of 6.3 to 6.7. This reformulation did lower the incidence of struvite crystals in house cats. However, it apparently increased the number of cats that formed calcium oxalate crystals. So today, oxalate crystal problems outnumber struvite problems.

Why Is This Problem Much Worse In Male Cats?

Male cats have narrower, longer urethras (the tube leading from the bladder to the outside). If this tube gets blocked, the cat can not urinate and becomes extremely ill.

Female cats with the same problem are in distress due to the pain, but because the urethra is shorter and wider, they never loose the ability to urinate. In the few cats that develop actual bladder or kidney stones (calculi), sex is irrelevant – they can both obstruct.

Is This A Medical Emergency?

It is a medical emergency when your male cat cannot urinate. Urination is how the body cleanses itself of toxic waste products. Urination is also critical for the cat to keep the proper balance of minerals and water in its body. It doesn’t take long (24hrs) for cats that can not urinate to become depressed and for systems in their body to begin to fail. If you suspect blockage in your male cat during the day, take it to your veterinarian immediately. If their office is closed, take the pet to a 24-hr emergency veterinary center.

When urine backs up into the pet’s kidneys, the pressure within the kidneys goes up. This will cause irreversible kidney damage if the pressure is not relieved. Three days in this condition is often fatal.

You can confirm that your cat is blocked if you feel a hard lemon-to-orange size “ball” in the lower rear abdomen. If the cat is still strong enough, it will cry when you attempt to feel it. Do Not Squeeze Its Tummy Firmly. Obstructed bladders can be easily popped. Even if you feel nothing, bring the cat to a veterinarian to have it checked there as well.

Experienced veterinarians can identify the male cats with FLUTD that are at most risk for blockage. When the bladders of these cats are expressed, the stream of urine is very narrow. This is due to swelling and inflammation of the urethra. Some of these cats suffer from chronic urethral and bladder inflammation (idiopathic cystitis/urethritis) that leads to a swollen, narrowed passage for urine. The urethras of those cats are more likely to block or obstruct with debris. ( ref1, ref2 )

How Will My Veterinarian Restore My Cat’s Ability To Urinate?

We will try to break down the blockage in the least traumatic way possible. Trauma to the urethra causes it to swell – then the likelihood or the cat blocking again becomes greater. I believe that an attempt should be made in all cats – except the most critically ill – to relieve their urethral obstruction without catheterization. Most veterinary cat catheters are considerably more rigid than the ones used in human medicine and thus more likely to cause damage. When I do have to catheterize cats, I try to use the much-softer catheters designed for intravenous use. Over half of all obstructed cats can be unblocked without resorting to catheterization. (ref)

The plug that blocks male cats is composed of mineral crystals and cellular debris. It has the consistency of cottage cheese. In many male cats, this plug is only near the tip of the penis. In these cats, gentle massage of the penis often breaks down the plug and allows the cat to urinate with a little assistance. This is the first method that I try.

If gentle pressure on the bladder and massage of the penis is not sufficient, many veterinarians use a small, soft catheter to “jet” a stream of saline around the plugs and flush them out. This is called retropropulsion.

If that is still unsuccessful, the veterinarian will have to catheterize the cat. Using the retropropulsion technique, a very small, catheter is slowly advanced into your cat’s bladder. Sometimes the bladder has been over-distended so long that the urine must be removed through the catheter with a syringe. The color and consistency of the urine is a good indication as to how long the cat was blocked and how much damage has already occurred.

Pets that are still fully conscious often need to be sedated or anesthetized to pass a catheter into their bladder. In the sickest animals, it can be done without these drugs. Once the blockage is removed, the pet will be given intravenous fluids and buffers to correct electrolyte (salt ion) imbalances, flush out its kidneys and encourage urination. Once that is done, the cat’s kidney function needs to be tested to see what damage, if any has occurred.

Most cats will pull their catheter out if they do not wear a sunflower-like collar. They need to stay at the animal hospital until the staff is pretty sure the pet will not plug again. It is also important that their kidney function, and water consumption return to normal before they leave. They may also receive antibiotics and medications to relieve pain and help relax the urethra. If the cat is to be sent home before this , I have the owners bring the pet in twice a day to be sure the bladder is emptying and that it is doing well.

What Are My Cat’s Chances Of Surviving?

The most important factor is how long your cat could not urinate before the problem was discovered. The longer a cat remains blocked, the sicker it will become. Markers for toxic products will increase to toxic levels in its bloodstream (BUN aka SUN over 80mg/dL), (creatinine over 6mg/dL); its blood potassium level will continue to increase to dangerous levels (over 8mmol/L), and its blood pH will continue to decrease to dangerous levels (less than 7.1 pH). You can view the normal blood values here.

The second bad consequence of long standing obstruction is lack of blood circulation in an over-stretched bladder. At some point, the bladder tissue damage becomes irreversible. Cats with subnormal body temperature (less than 96F 35.6C) and a heart rate of less than 120 beats per minute are also at extreme risk.

What Medical Treatment Will My Cat Need?

Pain Control

This is a painful condition for your cat. A pain control medication called butorphanol or buprenorphine can help with this (Some veterinarians use Non-steroidal anti-inflammatory agents such as Metacam® for the same purpose).

Stress Control

Obstructed cats need to be housed in a darkened, secluded room by themselves. They need to concentrate on urinating – not on strange dog and cat odors and sounds. Tranquilizing them with medications like acepromazine can be quite helpful.


These are drugs to relax the urethra and bladder wall. When these areas are inflamed, they go into spasm, causing pain and making obstruction more likely to reoccur. So it would seem that medications to minimize this would be helpful. Two that are commonly used are propantheline and oxybutynin. However, some veterinarians feel they do more harm than good and use Valium® for much the same effect.


Medetomidine is another sedative and pain-relieving medication that can help relax the cat’s urethra until the acute inflammation passes.


In most cases they are probably unnecessary. But they are still commonly dispensed to cats that have had a FLUTD episode. Bacteria use indwelling (left in place) urinary catheters to move up into the bladder and kidneys. So protecting pet in this situation with antibiotics may be wise. Also cats with significant bladder damage, due to over-stretching, probably do not have their natural resistance to bladder infection. In these cats, antibiotic cover is a wise choice also.

Increased Water Consumption

The more water your cat consumes, the more dilute its urine will be and the less likely it will be that crystals form. So encouraging your cat to drink is important to cure it of its current problem and to prevent future relapses. Heavy urine production also helps flush crystals and debris out of the urinary tract. Cats are not by nature big drinkers. But changing their diet to canned food will supply them with more water. You can add a meat broth to the canned food to supply even more water. Be sure one or more water bowls remain full all day. Try putting them in novel containers, fountains and locations to increase the pets curiosity. Some veterinarians suggest distilled water. There is no harm in giving distilled water – but ordinary, tap water that meets EPA standards is fine.

Reduce Stress In Your Cat’s Life

Cats are creatures of habit. They often break with FUS/FLUTD during periods of stress. This may be a move to a new location, the introduction of another cat or a diet change. If at all possible, try to return the situation to what it was before the problem occurred. If you can not do that, be sure your cat has some private space to itself. Some owners find pheromone products like Feliway™ or catnip helpful. If you have a multi-cat household, the problem becomes more difficult. Some cats just don’t like the company of other cats. Do what you can to give each of them their own, separate space, food, water bowels, and litter boxes.

Some veterinarians have found that dispense amitriptyline, an anti-anxiety medication, seems to reduce the reoccurrence of urinary tract obstruction. Amitriptyline is a human anti-anxiety medication (Elavil). But the drug also has a relaxing effect on the muscles that surround the bladder and urethra. In humans, this can be a worrisome side effect because it becomes difficult to void a relaxed bladder. But in cats, it may be a positive effect in relieving urethral spasms. (ref)

Glucosamine Supplements?

Glucosamine and chondrotin have been recommended for cats with this urinary problem. They are the building blocks of the protective glycosaminoglycan coating of the bladder. Pentosan polysulfate which is marketed for relief of interstitial cystitis in humans and Adequan, used for arthritis in pets, have also been used. I have little faith in any of them, but there is no harm in giving either.

Urinary Acidifiers For Struvite Crystals

Struvite crystals dissolve when a cat’s urine is acidified. However, it is much more effective if this is accomplish using a commercial diet that is designed to produce an acid urine than by giving urine acidifiers. There effect is quite short lasting and they taste bad. If your cat is in the middle of an FLUTD crisis, feed a diet furnished by your veterinarian or make one yourself. There are services that will provide you with special recipes. (ref) If the problem is mild or the cat’s urination appears normal, you can try a non-prescription diet formulated for lower urinary tract health (such as Purina Special Care Formula) or find recipes for home cooked meals here.

Potassium Citrate When The Crystals Contain Oxalate

This compound has been shown to raise the pH (lower the acidity) of urine. Oxalate crystals only form in acid urine – so reducing the acidity should help prevent them. Potassium citrate will not dissolve crystals or stones that have already formed. If true stones are present that are too large to pass through the urethra,, they will have to be removed from your cat surgically.

Would Surgery Help?

A few cats with FLUTD have actual granules of mineralized material plugging up their urethra and bladder. In these animals, the bladder must be opened and the material removed. This surgery is called a cystotomy.

But in the majority of cats, the material is fine and pasty. When cats with this more common form relapse despite everything you do, the best solution may be a surgical procedure called a perineal urethrostomy.

This surgery works best in male cats that have a very narrow portion of urethra near the tip of their penis but in which the remainder of the urethra is adequately wide. In these cases, plastic surgery restructures that narrow portion to prevent debris and crystals from blocking again. It does not prevent the crystals and debris from forming. When the surgery is complete, your cat will look allot like a female cat.

This surgery can be the only way to save the life of your cat if diet, medication and life style changes do not control FLUTD. However, it is not always successful. Also, cats that have had this procedure are also more prone to bacterial infections  gaining access to their urinary system. So they need to be monitored throughout their lives for urinary tract infections. If found, these infections can be controlled or eliminated with antibiotics.

What Causes Feline Urological Syndrome?

The short answer is that we do not know. We do know that overweight cats, cats consuming dry cat food, cats that do not drink adequately and cats in multi-cat households are more at risk. But we see FLUTD is cats that do not fit in that group. In those cats, veterinarians think that perhaps genetics, and even the age at which they were neutered  might be factors.

Occasionally, an underlying cause is detected. But in the majority of cases, no underlying cause is found.

In the cases where struvite is the problem, anything that causes the urine to be less acidic or more concentrated is thought to make the problem more likely to occur.

In the case where oxalate is the problem, too acid a diet and insufficient water consumption are probably involved. Genetic factors probably also play a part because Burmese and Himalayan cats have more than their share of oxalate problems. On the average, oxalate problems develop in cats at a bit older age than struvite. In many cases, cats with oxalate problems were found have blood calcium levels that were too high. (ref).

Will This Problem Return? What Can I Do To Prevent A Relapse?



We currently have no way to predict that for individual cats such as yours. Some cats have only one incident of FLUTD in their live. Others have repeated episodes despite all veterinarians do to prevent them. Until we understand the causes better, I can only give you general suggestions. It’s been said that that the reoccurrence rate of FUS is about 35% – although that would be very hard to truly document.

Here Is Some Advice That Might Help”

1) Monitor the amount and characteristics of your cat’s urine for specific gravity with a refractometer and for acidity and the presence of unseen blood with paper dipsticks similar to the ones in the photograph.

2) Monitor the specific gravity of your cat’s urine to be sure it is consuming enough liquid to keep its urine quite dilute.

3) Keep your cat’s litter box clean and placing it in a low-traffic area. If you have more than one cat, have proportionally more litter boxes.

4) Feed a prescription or home cooked diet that is formulated to prevent struvite or oxalate formation. There are many brands on the market. I prefer the canned types over the dry types. Dry chows are convenient, but cats that consume them tend not to drink proportionately more to meet their hydration needs.

5) Do everything you can to encourage your cat to drink more.

6) Minimize stressful changes in your cat’s routine, environment and diet.

What Type Of Diet Changes Might Help?

If The Problem Is Struvite:

Veterinarians sell many brands of diet that are formulated to help prevent struvite FLUTD. These diets do this by promoting acidic urine. As i mentioned, I would prefer your feed cats with FLUTD a canned diet. However, you will need to be sure your cat does not put on excess weight.

It is also important that your cat munches throughout the day – as cats like to do. By eating small amounts frequently, your cat will minimize the tendency to have alkaline urine (high pH) shortly after a large meal.

No mater what you feed a cat with a struvite crystal problem, it is important that you keep track of its urine pH. It should stay below 6.5 most of the day. If you follow the link next to the title of this article, you will see the materials you will need to do this. You can also follow that link here.

If The Problem is Oxalate:

If your cat was found to be hypercalcemic (too much calcium in the blood) the cause for that needs to be looked into and corrected if possible.

If your pet’s blood calcium level is normal, veterinarians also sell many brands of diet that are formulated to help prevent oxalate formation. These diets are high in fiber and have only the amount of protein required by cats. They promote a urine pH that is not in the range where oxalate crystals are likely to form.

It appears that having specific meal times for your cat rather than food available at all times, also helps keep the pet’s urine pH closer to neutral.

Do not allow your cat to consume Vitamin C supplements.

You can collect a few drops of your cat’s urine by placing a sheet of clear plastic film over the litter or purchasing special litter designed for that purpose. If you can, monitor your pet’s urine pH and specific gravity. You can purchase strips that record the pet’s urine pH and purchase a small device called a refractometer to measure urine specific gravity. It is very easy to use. Cats are most likely to do well if their urine pH remains between 6.0 and 6.5 and cats with either form of FUS are most likely to do well if their urine specific gravity remains between 1.015 – 1.020 most of the time. You can purchase an inexpensive refractometer on line. As urine sits after it is collected, its pH rises. So do your tests on recently voided samples.

Bring a urine sample in to your veterinarian occasionally to be checked for the presence of distinctively shaped oxalate crystals. It is of no concern for there to be a few struvite crystals in urine – particularly if it has been standing for a time. If a minimal number of crystals are of importance, there should be an increased number of white blood cells in the urine and, perhaps, traces of blood (occult blood) as well.

If oxalate crystals are still present after diet change, urine pH modification, and increased fluid intake, one should consider giving the cat a potassium citrate supplement.

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