When Your Cat Can’t Pee – Feline Urological Syndrome

When Your Cat Can’t Pee – Feline Urological Syndrome

aka FUS /Feline Lower Urinary Tract Disease (FLUTD)

Ron Hines DVM PhD

The problem that brought you to this page has many long names. I still call it FUS (feline urological syndrome), although that name is no longer in vogue (fashionable). This urinary tract problem is thought to be responsible for 2-13 % of cat veterinary visits worldwide. More accurate numbers are unavailable, but I believe that FUS incidence depends on the diets commonly being fed (dry kibble versus wet ingredients) and an indoor versus an outdoor lifestyle that leads to a lack of exercise and obesity.  (read here, here & here) Many cat owners arrive at their veterinarian’s office believing that their cat just has an etiquette problem – either too much time spent in the litter box, urinating outside of the box or spraying furniture and other objects. (read here) Others are sure that their cat is constipated. A few believe that their cat is straining because it has worms (particularly when they see tapeworm segments on its stool) . When your cat can no longer pass urine (blocked) the signs are considerably more severe. Although both male and female cats suffer from FUS/ FLUTD ; it is only a life-threatening disease when your cat is a male. Female anatomy makes blockage of your cat’s urine passageway considerably less likely. 

FUS is a perplexing disease. Veterinarians and nutritionists do not understand why one cat in a household develops urinary tract problems while other cats in the same household do not. When FUS/ FLUTD occurs, it is because sharp crystals have fallen out of solution in your cat’s urine while the urine is still in your cat’s bladder. These crystals irritate your cat’s bladder lining as well as the urethral passage. When these crystals mix with cellular debris sloughed from the cat’s bladder lining, they can form plugs that prevent male cat from passing urine. In female cats, the irritation these crystals produce cause her urination behavior to change. She has more urges to urinate. Irritation and inflammation in both sexes can progress to the point where blood or clots are present in the urine. (read here)

What Kind Of Cats Are Most Likely To Develop FUS?

Cats of any age are susceptible to lower urinary tract problems. But the average age is said to be about 4 when signs begin. It is quite uncommon for FUS to occur in cats under 1.5 years of age. Older cats also develop FUS/ FLUTD. But when they do they usually have some other underlying health or chronic stress issue. That stress might be a new feline arrival, a move to a new residence, or even a new feral cat taking up residence near a window. Some veterinarians claim to see FUS more frequently in Persian cats; others that Siamese cats have the problem less frequently than other breeds. I do not know of anyone that confirmed that this was more than a coincidence. Until the mid 1990s, the urine crystals that veterinarians encountered were usually composed of the mineral, struvite (ammonium-magnesium-phosphate). But since then, the incidence of calcium oxalate urine crystals has mysteriously increased until currently they make up more than half the diagnosed cases of FUS. I think of this 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. I have treated cats in Texas, Florida, the Cayman Islands, Costa Rica and the Middle East. I do not recall a single cat that spent the majority of its time outside the home that developed FUS/FLUTD. 

If My Cat Develops FUS What Signs Might I See?

I mentioned that the first thing many cat owners notice is that their cat is spending too much time in it’s litter box and/or urinating outside its litter box. You can read an article specifically about that problem here. I also mentioned that 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 and I palpate no hard stools in the colon, I suspect a urinary tract 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. The penis of males may no longer withdrawn entirely into its sheath and might be bluish or inflamed at its tip. There may be a white, cheese-like material surrounding the penis and sheath. Those cats are particularly prone to obstruct (plug up) if they haven’t already done so. They seem to find sinks, tubs, open drawers and closets particularly attractive as new elimination areas. 

What Is Going On In My Cat?

I also mentioned that when FUS/ FLUTD occurs, small sharp crystals form in your pet’s urine, irritating the bladder and urethral 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 minerals (ash). That seemed logical. The only problem was that no one was able to reproduce the disease by feeding high ash/magnesium diets to normal test cats. Some constituents of pet food ash are necessary (calcium and trace minerals) – however, cheap cat foods are often much higher in ash than they should be.

So other factors must be at work. Some speculate that bacteria or virus are involved. However most cats with an FUS/ FLUTD problem have no or few bacteria or virus in their urinary tracts and when transferred to healthy cats they cause no disease. When bacteria are found in your cat’s voided urine, they are often no more than contaminants from the pet’s penis or vagina. However, when bacteria are present in urine obtained sterile through a needle (cystocentesis) they need to be eliminated. The presence of white blood cells in your cats urine is also an indication of infection. 

Another thought was that lethargic, indoor cats do not drink enough water. They rarely do. We know that struvite and oxalate crystals occur more frequently in concentrated (supersaturated) urine. However, just as we could not cause the disease with high ash diets, producing concentrated urine didn’t cause the disease either. (read here  & here)

Struvite crystallizes 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 acidic urine (as low as 6.3). This reformulation did lower the incidence of struvite crystals in house cats successfully. However, it apparently increased the number of cats that formed calcium oxalate crystals instead. So today, oxalate crystal problems outnumber struvite problems and FUS / FLUTD diets have been reformulated primarily to keep your pet’s urine dilute and low in both struvite and oxalate components with a pH slightly below 7. 

Why Is This Problem So Much Worse In Male Cats?

Male cats have narrower and longer urethras, the tube leading from their bladder to the outside. If this tube gets blocked, your cat cannot urinate and rapidly becomes quite ill due to the buildup of toxins (the end products of normal metabolism). The diameter of this tube is particularly narrow as it reaches the distal end of your cat’s penis. The generalized illness produced is similar in nature to uremia. You can read about that here. But in addition to a buildup of the toxic products of metabolism, the abnormally high urine pressure in a blocked cat’s bladder rapidly starves bladder tissue of oxygen. Tissue starved of oxygen rapidly deteriorates, liberating even more undesirable compounds. 

Female cats with the same problem are in distress due to pain. But because their urethra is shorter and wider, I have never seen one that lost the ability to urinate. In the few cats that develop actual bladder or kidney stones (calculi) that block urine flow, sex is irrelevant – they can both obstruct.

Is This A Medical Emergency?

It is always a medical emergency when your male cat cannot urinate. As I mentioned, urination is how your cat’s body cleanses itself of toxic waste products. Urination is also critical for your cat to keep the proper balance of minerals and water in its body. It doesn’t take long (~24 hrs) 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 him to your veterinarian immediately. If their office is closed, take your pet to a 24-hr emergency veterinary center.

When urine backs up into your cat’s kidneys, the pressure within the kidneys goes up. That can cause irreversible damage to fragile kidney filters 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 cat’s lower rear abdomen. If the cat is still strong enough, it will probably cry when you gently attempt to press in that area. NEVER SQUEEZE ITS TUMMY FIRMLY. Obstructed bladders tear easily. Even if you feel nothing, bring your cat to your veterinarian to have it checked there as well.

Experienced veterinarians learn to identify the male cats with FLUTD that are at the most risk for future blockage. When the bladders of those cats are expressed, the stream of urine is very narrow. Part of that could be anatomical, but often it is due to chronic swelling and inflammation of the urethra that is already present. Those are the cats that suffer from chronic urethral and bladder inflammation (idiopathic cystitis/urethritis) that leads to a swollen, narrowed passage for urine. Because of that, the urethras of those cats are more likely to block or obstruct with debris. (read here  & here)

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

Veterinarians try to eliminate your cat’s urethral blockage in the least traumatic way possible. Catheterization carries the risk of traumatizing its fragile urethra. That can cause swelling that decreases the tube’s diameter. If that occurs, the likelihood of your cat blocking again becomes much greater. I believe that an attempt should always be made (except the most critically ill cats)  to relieve urethral obstructions without catheterization. One author believes that over half of all obstructed cats can be unblocked without resorting to full catheterization. (read here)  When a catheter is required I have had better success using the much softer 22 G catheters designed for intravenous use in humans than those sold as “tom cat” catheters.

The plugs that block male cats is composed of mineral crystals and cellular debris. That material has the consistency of cottage cheese. In many male cats, this plugging material is only compacted near the tip of their penis. In those cats, sedation, gentle massage of the penis and mild pressure on the abdomen often breaks down the plug and allow the cat to void its bladder with only a little assistance. Within a matter of hours, most cats regain bladder muscle tone that allows them to urinate on their own. This is the first method that I try. When successful, I follow that with generous amounts of subcutaneous fluids to maximize urination. 

When gentle pressure on the bladder and massage of the penis is not sufficient, many veterinarians including myself use a small, soft catheter to “jet” a stream of saline around the plugs to encourage them to flush out. This is called retropropulsion. It is similar to veterinary hydropropulsion that is often effective in removing small urinary tract stones blocking the urethra. (read here)

If that is still unsuccessful your veterinarian will probably have to catheterize your cat.  Using the retropropulsion technique to expand the urethra’s diameter as much as is safely possible, 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 tissue damage has already occurred. 

These pets need to be sedated or anesthetized whenever these techniques are attempted. Many of these cats are already “toxic” with blood electrolyte imbalances so they are at a considerably higher anesthetic risk.  Your vet is aware of that and will adjust drug doses accordingly. Once the blockage has been removed, your pet will probably be given intravenous fluids and buffers to correct those earlier imbalances, flush out its kidneys and encourage urination. Once successful, it is always wise to have your  cat’s kidney function tested, (BUN  &  creatinine) a few days later to be sure that no lasting kidney damage has occurred.

Most cats requiring a catheter will pull it out if not wearing a sunflower-like (Elizabethan) collar. They need to stay at your local animal hospital until the staff is pretty confident your pet will not plug again. Your cat might also require antibiotics and medications to relieve pain and help relax its urethra. When for one reason or another a cat has to be sent home before I am confident the problem is behind it, I have the owners bring the cat in twice a day to be sure its bladder is emptying and that it is doing well.

What Are My Cat’s Chances Of  Recovering?

The most important factor is how long your cat could not urinate before the problem was discovered. The longer a cat remains unable to urinate, the sicker it becomes. The longer your cat’s bladder remains over distended, the more bladder tissue damage is likely to occur. The longer urine pressure in your cat’s kidneys remains above normal, the more nephron damage is likely to occur. With time, markers for toxic products in circulation increase. I already mentioned BUN and creatine. They are just convenient markers that veterinarians use to measure for a host of other undesirable products normal kidneys dispose of through urination.  Depending on how long your cat has been obstructed,  toxic levels in its bloodstream (BUN aka SUN > 80 mg/dL), (creatinine > 6 mg/dL), blood potassium level can also increase to dangerous levels (> 8 mmol/L), and  blood pH might also decrease to a dangerous level (< 7.1 ). You can view all the normal blood values of cats here.  Cats with subnormal body temperature (less than 96 F / 35.6 C) and a heart rate of less than 120 beats per minute are also at extreme risk. (read here) In humans  with urinary tract obstructions, urine NGAL level is also measured as an indicator of the degree of kidney damage that might have occurred due to increased urine back pressure. Some believe that it is a more sensitive indicator than creatinine. NGAL has only been measured experimentally in cats. 

What Medical Treatment Will My Cat Probably Need?

Pain Control

As you can imagine, this is a very painful condition for your cat. Pain control medications called butorphanol ( Torbutrol®  ) and buprenorphine ( Simbadol® ) can help. Some suggest medetomidine (Domitor®). Others combine more than one agent. 

Other veterinarians find Non-steroidal anti-inflammatory agents such as meloxicam (Metacam®) sufficient. Metacam® is FDA-approved for cats as a single dose to control postoperative and other forms of pain. In cats, more than one dose has been associated with kidney damage. Perhaps I am overly cautious but I never give this product to cats.  (read here)

Stress Control

Obstructed cats need to be housed in a dimly lit , secluded room by themselves. They need to concentrate on urinating – not on distractive dog and cat odors and sounds. Tranquilizing them with medications such as acepromazine at appropriate doses can be quite helpful. Acepromazine combats dysphoria, it is not believed to lessen pain sensation. 


These are drugs that relax your cat’s urethra and bladder wall. When these areas are inflamed, they go into spasm, causing pain and making a second obstruction more likely to occur. So it would seem that medications to minimize that would be helpful. Two that had been suggested in the past were propantheline and oxybutynin. However, most veterinarians feel they do more harm than good and, if at all, use low doses of diazepam (Valium®) for much the same effect. 


The medetomidine  ( Dormitor® ) mentioned earlier is another sedative and pain-relieving medication that can help relax your cat’s urethra until the acute inflammation of obstruction has passed.


In most cases they are probably unnecessary. (read here) But antibiotics are still commonly dispensed to cats that have had a FLUTD episode involving obstruction. The most common one is probably Augmentin®/Clavamox® . Clever bacteria use indwelling (catheter left in place) urinary catheters as “ladders”  to move up into your cat’s bladder and kidneys. (read here) So protecting your cat in this situation with antibiotics might be wise. Also, cats with significant bladder damage due to over-stretching (distention) probably do not have their natural resistance to bladder infections. In these cats, antibiotic cover (prophylaxis) could be a wise choice as well.

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 and sediment form. So encouraging your cat to drink is important to cure it of its current problem as well as to prevent future relapses. Heavy urine production also helps flush crystals and debris out of the urinary tract before clogs can occur. Cats are not by nature big drinkers. They were designed by Nature to obtain sufficient water from the rodent prey they ate (rodents are 70-80% water). But changing your cat’s diet to a canned or home-prepared  food will supply them with more water. ( read here & here ) Alternatively, you can very gradually add a meat broth to the canned or dry food that your cat currently eats to supply even more water. Be sure one or more water bowls remain full throughout the day. Try putting them in novel containers, fountains and locations to increase your pet’s interest in them. Some veterinarians suggest distilled water. There is no harm in giving distilled water – but ordinary, tap water that meets EPA standards is fine. You might also give Hydra Care® a try. If you do, let me know the results and I will post them. 

Reduce Stress In Your Cat’s Life

Cats are creatures of habit. They often break (develop symptoms) with FUS/FLUTD during periods of stress. That might 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. Cats are as different as people. Some cats just don’t like the company of other cats. Do what you can to give each of your cats their own separate space, food, water bowels, litter boxes and love.

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

Glucosamine Supplements?

Glucosamine and chondrotin have been recommended for cats with urinary tract problems. Both are building blocks of the protective glycosaminoglycan coating of the bladder. Pentosan polysulfate which is marketed for relief of interstitial cystitis in humans and Adequan® marketed for arthritis in pets have also been used. I have little faith that any of them are significantly beneficial for urinary tract issues or arthritis in cats (or dogs) receiving nutritionally-adequate diets, but there is no harm in giving them. (read here)

Urinary Acidifiers For Struvite Crystals

Struvite crystals dissolve when your cat’s urine is acidic. However, it is much more effective if this is accomplish using a commercial diet that is designed to produce acid urine than by giving your pet urine acidifiers. The most common urine acidifiers  dispensed for struvite crystals are ammonium chloride and dl-methionine. Of the three, the first is the most effective. The most common one dispensed for oxalate crystals is potassium citrate. However  the  effects of all of them on urine pH is short lasting and they taste bad. Oral acidifiers must be used with caution, if at all, in cats that are already consuming a diet formulated to acidify your cat’s urine. If your cat is in the middle of an FLUTD crisis, feed a diet furnished by your veterinarian or hire a veterinary nutritionist service to guide you in making one yourself. There are services at many veterinary schools as well as Balance IT that will provide you with special recipes. (see here) If this was your cat’s first episode and its urination now appears normal, you can try a non-prescription diet formulated for lower urinary tract health (such as one of Purina  or Royal Canin’s urinary health formulas).

More About Potassium Citrate When Your Cat’s Crystals Contain Oxalate

As I mentioned, this compound has been shown to raise the pH (=lower the acidity) of urine. Oxalate crystals only form in acidic urine. So reducing the acidity (making your cat’s urine more basic) should help prevent the oxalate that is found in all cats urine from falling out of solution (crystallizing). Unfortunately, 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, your veterinarian will have to remove them from your cat surgically or with the aid of sophisticated “basket & YAG  laser apparatus” available at a few large veterinary centers such as the AMC the RVC  and the  UQ.

Would Surgery Help?

I mentioned that surgical or sophisticated apparatus are the only two ways I know of to remove urinary blockages that are composed of oxalate. A few cats with struvite-based FUS / FLUTD also have actual granules of that mineralized material plugging up their urethra and its entrance into the bladder. In those animals also, the cat’s bladder is usually opened surgically and the material removed. This surgery is called a cystotomy. However in the majority of cats, thankfully this material is fine-grained and pasty. When male cats with this more common form relapse despite everything your veterinarian can do, the best solution may be a surgical procedure called a perineal urethrostomy. This surgery works best in male cats that block because they have an abnormally narrow portion of their urethra nearest the tip of their penis, but in which the remaining upper portion of their urethra is adequately wide. In these cases, plastic surgery performed by your veterinarian restructures that narrow portion to lessen the chances that debris and crystals will blocking the channel again. The surgery does not prevent future crystals and debris from forming. Only a diet change, greater fluid intake, exercise and weight loss for obese cats will do that. When the surgery is complete, your cat’s privates will look allot like a female cat. This surgery can be the only option to save the life of your cat when diet, medication and life style changes do not control FUS / FLUTD. However, it is not always successful. Occasional cats I have performed this procedure on appear more susceptible to subsequent urethral and bladder infections. So they need to be monitored throughout their lives for urinary tract infections. If found, those infections can be controlled or eliminated with periodic antibiotics. Again, maintaining high water intake is critical to long term success. A second possible complication is chronic irritation of the surgically remodeled area that causes granulation tissue to form. Only the natural lining of your cat’s urethra is resistant to the chronic dampness and constituents of its urine. 

What Causes Feline Urological Syndrome?

The short answer is that we do not know. On rare occasion, perhaps an underlying anatomical cause might be detected. But in the vast majority of cases, no underlying anatomic or metabolic cause is found. When veterinarians don’t know the cause of something, they call it “multifactorial”. We do know that overweight cats, cats consuming dry cat food, cats that do not drink adequate water or consume sufficient water from their food and cats in multi-cat households are more at risk. But we see FUS / FLUTD is cats that do not fit into those groups. In those cats, some veterinarians believe that perhaps genetics, and even the age at which your cat was neutered might be contributing factors.  Burmese and Himalayan cats are said to have more than their share of oxalate problems. On the average, oxalate problems develop in cats at a bit older age than struvite. In some cases, cats with oxalate problems were found have blood calcium levels that were too high. (read here)  Burmese and Himalayan cats are said to have more than their share of oxalate problems. On the average, oxalate problems develop in cats at a bit older age than struvite. In the cases where struvite crystal formation is the problem, anything that causes your cat’s urine to be less acidic or more concentrated is thought to make the problem more likely to occur. Suspicion often falls on cats receiving inappropriate diets for what is basically a carnivorous animal. Despite fancy cat food ingredient lists and cat food company commercials, your cat’s nutritional needs are not the same as yours.  (read here)

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


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

Here Is Some Advice That Might Help:

 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.

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

 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.

 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.

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

 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 “prescription” diets that are formulated to help prevent struvite-related FUS/FLUTD. These diets do this by promoting acidic urine and thirst. They are more expensive. That is not because the ingredients they contain cost more. It is because the companies manufacturing them are intent on maximizing their profits. Do you rely on your common sense or text your physician for approval before ordering what appeals to you on your restaurant menu? As I mentioned, I would prefer your feed cats with FUS / FLUTD a canned or home-prepared moist diet. However since home-prepared diets are more flavorful, you will need to be sure that 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 6.8 most of the day. If your cat is consuming sufficient water, the specific gravity of its urine should stay below about 1.035 most of the day. The diagram photo above shows the materials you will need to do this at home, a medical refractometer and test paper colorimetric strips. Their use at home is easily mastered by watching YouTube videos. Test samples shortly after they are voided. As urine sits after it is collected, its pH rises. Don’t forget about Hydra Care® and  let me know  what your cat thinks about it.

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 when possible. (read here) If your pet’s blood calcium level is normal, veterinarians also sell many brands of feline diets that might help prevent oxalate crystal formation too. Many of these diets are higher in fiber and have only the amount of protein content actually required by cats. They also promote a urine pH that is not in the range where oxalate crystals are likely to form. They encourage thirst which keeps your cat’s urine dilute. That is probably their most important attribute.

Some suggest that having specific mealtimes for your cat rather than food available at all times, also helps keep your pet’s urine pH closer to neutral (pH 7). I do not know if that has been verified but there is no harm in doing so. 

Bring a fresh sample of your cat’s urine to your veterinarian occasionally to be checked for the presence of distinctively shaped oxalate or struvite crystals. Call ahead to inquire when the nurses are likely to have free time to immediately check the sample. It is of no concern for there to be a few struvite crystals in urine – particularly if the sample has been standing for a time. In deciding if a minimal/moderate number of crystals are of importance, an increased number of white blood cells and, perhaps even traces of blood (invisible blood = occult blood) in the urine add significance to the finding of a minimal/moderate number of crystals in fresh urine samples. (read here)

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