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This page is in serious need of updating, which I hope to complete during 2017.


What is FLUTD? Causes of FLUTD


Crystal Types
Struvite Crystals Calcium Oxalate Crystals Interstitial Cystitis


Symptoms Diagnosis Blockages


Struvite Crystals Calcium Oxalate Crystals Interstitial Cystitis


Feed Tinned Food Avoid Obesity Feed Little and Often
Repair the GAG layer Reduce Stress Grow Older


Links Harpsie's Experiences


What is FLUTD?

FLUTD stands for Feline Lower Urinary Tract Disease. It was previously known as Feline Urological Syndrome or FUS, but the name was changed to more accurately reflect the condition.


FLUTD is an expression used to cover a number of problems with the urinary tract. It is not the same as a urinary tract infection. Urinary tract infections are caused by bacteria, whereas only about 2% of cats with FLUTD actually have an infection - their problems tend to have other causes.


The cause of FLUTD is never known in around 50% of sufferers, and in this case it is often called interstitial cystitis.


FLUTD is more common in male cats who are overweight and who eat a dry food diet. Persians like Harpsie appear to be more prone to FLUTD.


This page summarises Harpsie's experiences with FLUTD, and therefore it primarily focuses on struvite crystals and urinary tract blockages, though I do provide some information on calcium oxalate stones and interstitial cystits. I am currently working on a FLUTD website (not yet active) which will cover all aspects of FLUTD in more detail. In the meantime, you may find the links below helpful.


Causes of FLUTD


In many cases of FLUTD, the problem is caused by an imbalance in the urine pH (acidity level of the urine). This imbalance in urine pH may cause stones or crystals (also known as uroliths or urolithiasis) to develop.


It is natural for cats to have a few crystals in their urine, as Cornell University College of Veterinary Medicine explains. However, in cats with FLUTD, the urine pH may become very unbalanced, and more crystals may be present than usual (although this is not always the case).


It used to be thought that ash was a factor in the development of FLUTD, and for a while low ash foods were all the rage. It is now known that ash levels are not linked to the development of FLUTD. Pet Education explains more about this.


It is thought that stress plays a role in whether a cat has an attack of FLUTD.


Mar Vista Vet has an overview of FLUTD.


Crystal Types

There are two main types of crystal or stones:

  1. Struvite Crystals

  • Cats whose urine is too alkaline (urine pH over 6.5) may develop struvite crystals. This type of crystal is composed of magnesium ammonium phosphate and is more common in younger cats;

  1. Calcium Oxalate Crystals

  • Cats whose urine is too acidic (urine pH under 6) may develop calcium oxalate crystals. This type of crystal is more common in older cats. About one third of cats with calcium oxalate crystals have high levels of calcium in their blood (hypercalcaemia).

Both types of crystals may cause problems in the bladder or urinary tract, such as irritation, inflammation, and, in the worst case, a complete urinary tract blockage.


Struvite crystals used to be more common in cats than calcium oxalate crystals. However, following the general acidification of many commercial foods (such foods often have something like "formulated for optimal urinary tract health" on the tin or packet), the opposite problem of calcium oxalate crystals and stones is becoming increasingly common. This is a worry because it is far harder to treat calcium oxalate crystals.


Mar Vista Vet has a good overview of struvite crystals.

Mar Vista Vet has a good overview of calcium oxalate crystals and stones.


Interstitial Cystitis

The cause of FLUTD is never known in around 50% of sufferers, and in this case it is often called interstitial cystitis.


Mar Vista Vet has more information about interstitial cystitis.

Non-obstructive idiopathic/interstitial cystitis in cats: thinking outside the (litter) box (2007) is a presentation by DJ Chew and CAT Buffington to the World Small Animal Veterinary Association World Congress 2007 which discusses interstitial cystitis.




Symptoms of FLUTD depend upon the type of problem, but may include:

  • frequent visits to the litter tray, with sometimes not much urine being produced;

  • the cat may sometimes lie in the litter tray (though Harpsie used to do this sometimes anyway, so it was not a sign of a blockage in his case); but if it is a new behaviour, it might be;

  • the cat may be straining to urinate (stranguria);

  • constantly washing the genital area;

  • blood may be visible in the urine (haematuria);

  • The cat may urinate inappropriately (outside the litter tray) - the cat does this because s/he associates the pain s/he is feeling with the litter tray, and therefore urinates elsewhere in the vain hope that it will not hurt in the new location;

  • The most serious symptom, which fortunately is not seen in every case of FLUTD, is the inability to urinate at all - see urinary tract blockages below.

Urinary Tract Blockages

Urinary tract blockages can occur when struvite crystals combine with something called a protein matrix and form a urethral plug, which stops the urine getting past it. This is more common in male cats, because the male urethra has a little "kink" where these plugs can form.


In cats with calcium oxalate crystals, the crystals may form stones and cause a blockage in the bladder. Occasionally problems occur further up the urinary tract, as far up as in the kidneys.  


If your cat is unable to urinate, as happened to Harpsie, it is a MEDICAL EMERGENCY and you must seek veterinary help IMMEDIATELY. If you do not, your cat could die a horrible, painful death. Because the cat is unable to urinate, potassium cannot be excreted and may build up in the body, eventually causing a heart attack. Alternatively, the cat will develop acute renal failure, and/or may even suffer a ruptured bladder. None of these is a nice way to go, so please seek help as soon as you suspect that your cat may be blocked.


Mar Vista Vet has more information about urinary tract blockages.



A urine sample will be taken and the urine examined for abnormalities, such as blood, infection or crystals. Bloodwork may also be run.


In some cases, an ultrasound or x-rays will also be performed. If larger bladder stones are present, these will usually be visible on x-ray.




Many cases of FLUTD resolve by themselves within two weeks. However, the condition is obviously uncomfortable, so treating it helps the cat, though care must be taken if acidifying the urine not to go too far.


Since infections only rarely accompany FLUTD, antibiotics are not usually necessary, though they may be given as a precaution to a cat who has been catheterised for a urinary tract blockage or to try to flush out calcium oxalate crystals, because such catheterisation increases the risks of infection.


Struvite Crystals Treatment

The goal is to dissolve the struvite crystals, and this can usually be achieved via diet. Because these crystals develop in urine that is too alkaline, a prescription acidifying diet is fed to the cat for about 4-6 weeks in order to dissolve the crystals - one popular brand is Hill's s/d, though all the main manufacturers make these foods. If your cat will not eat one brand, your vet should be able to obtain samples from other manufacturers for you to try.


Once the struvite crystals have dissolved, another prescription diet is normally prescribed which will maintain the correct urine pH levels, so the struvite crystals cannot reappear. This diet is fed on an ongoing basis. One popular brand is Hill's c/d. You should not feed these prescription foods to your healthy cats, because they may acidify the urine too far in such cats, thus causing the opposite problem of calcium oxalate crystals.


If your cat simply refuses point blank to eat these foods (which, like any new food, should be introduced gradually into your cat's diet), you should ask your vet's advice. What we did when Harpsie got bored with his maintenance diet was to feed one of the commercially available acidified diets (if a food says "to maintain urinary tract health", chances are it is acidified to a degree), and our vet also prescribed DL-methionine tablets, which are acidifying. These worked well for Harpsie (not least because he was easy to pill) but there can be side effects from these products, so you cannot use them forever.


In the worst case, for male cats who block repeatedly, the vet may recommend a type of surgery called perineal urethrostomy. This is basically amputation of the penis, so that the opening into the urethra is wider, and there is less chance of a blockage forming.


Calcium Oxalate Crystals Treatment

Unfortunately it is much harder to treat calcium oxalate crystals with diet. Occasionally they can be flushed out if the cat is put on IV fluids (a drip) but if this doesn't work, then normally surgery is necessary to remove the stones.


For some cats, calcium oxalate stones may be caused by a Vitamin B6 deficiency, in which case a Vitamin B supplement may help (be guided by your vet as to an appropriate brand).


If the cat has hypercalcaemia (high calcium levels), treating this may help. Possible treatments are discussed here.


Once the stones are under control, be careful not to feed any of the commercial cat foods labelled as being formulated for urinary tract health - chances are these are too acidifying for your cat, who is already prone to acidic urine. Your vet may recommend a prescription diet.


In humans, it is possible to use shock waves to smash the stones, a procedure known as lithotripsy. Unfortunately this is difficult to perform on cats, who are much smaller than humans. Ureteral dilemma: Non-surgical management of ureteroliths (2007) Adams LG Hill's Symposium on Lower Urinary Tract Disease 2007 pp14-21 mentions that their trials with this procedure were not successful (see page 19), but states that the equipment used may make a difference.


Mar Vista Vet gives a good overview of calcium oxalate stones.

Ureteral dilemma: non-surgical management of ureteroliths (2007) Adams LG Hill's Symposium on Lower Urinary Tract Disease 2007 pp14-21 discusses possible treatment options. Scroll down to page 14.

Management and outcome of cats with ureteral calculi: 153 cases (1984 - 2002) (2005) Kyles AE, Hardie EM, Wooden BG, Adin CA, Stone EA, Gregory CR, Mathews KG, Cowgill LD, Vaden S, Nyland TG, Ling GV. Journal of the American Veterinary Medical Association 226(6) pp937-44 discusses a large number of cases over a period of eighteen years, and states that even after successful treatment, many cats will have impaired renal function.

Oxalate degradation by intestinal lactic acid bacteria in dogs and cats (2004) Weese JS, Weese HE, Yuricek L, Rousseau J Veterinary Microbiology 101(3) pp161-6 mentions that the use of prebiotics, including fructooligosaccharide products (FOS), a type of fermentable fibre, may help reduce the formation of calcium oxalate stones.


Interstitial Cystitis Treatments

Anti-inflammatories are often used to help treat interstitial cystitis. Reducing stress is also essential. Since this problem appears to be more common in indoor-only cats, environmental enrichment may also help.


Mar Vista Vet has more information about treatment options.

The Indoor Cat Initiative at Ohio State University College of Veterinary Medicine states that feeding dry food may contribute to this problem and gives suggestions on how to change your cat's diet.

Clinical evaluation of multimodal environmental modification (MEMO) in the management of cats with idiopathic cystitis (2006) Buffington CAT, Westropp JL, Chew DJ & Bolus RR Journal of Feline Medicine and Surgery 8, pp261-268 discusses how environmental enrichment can help cats with this condition.




Feeding Tinned Food

The single best thing you can do for a cat with FLUTD is to feed tinned (canned) food. This prevents dehydration and limits the favourable environment which stones need to form. If your cat refuses to eat such foods, do at least try to increase your cat's water intake, e.g. by adding extra water to his/her dry food, or by buying him/her a water fountain.


The Indoor Cat Initiative at Ohio State University College of Veterinary Medicine states that feeding dry food may contribute to FLUTD and gives suggestions on how to change your cat's diet.


Avoid Obesity

Try not to let your cat become obese, because this may be a factor in developing FLUTD (though Harpsie was certainly not obese). You should also minimise stress as far as possible for FLUTD cats, e.g. do not move the litter tray, try to maintain regular routines for the cat if possible.


A study of environmental and behavioural factors that may be associated with feline idiopathic cystitis (2004) Cameron ME, Casey RA, Bradshaw JW, Waran NK, Gunn-Moore DA Journal of Small Animal Practice 45(3) pp 144-7  mentions that obesity and stress appear to be factors in the development of FLUTD.


Repairing the GAG Layer

The GAG layer is a layer of cells within the bladder. It is often damaged in FLUTD cats. A number of products, such as those containing glucosamine, appear to help repair the GAG layer. Ask your vet which product s/he would recommend.

Oral glucosamine and the management of feline idiopathic cystitis (2004) Gunn-Moore DA & Shenoy CN Journal of Feline Medicine & Surgery 6(4) pp219-25 did not find the use of glucosamine of much benefit but on the other hand, it is unlikely to do any harm if you wish to try it.

Feline Advisory Bureau - has some information on repairing the GAG layer.

Cystease is one possible brand to try.

Cosequin is one brand containing glucosamine which is usually used for arthritis.


Feed Little and Often

It is sometimes claimed that cats with FLUTD should only be fed once or twice a day, because feeding them more frequently is supposed to increase the risk of stones forming, because of something called "post prandial alkalosis", where urine pH becomes more alkaline a few hours after eating. However, cats did not evolve to eat only once or twice a day. The National Academy of Science has recently done some in-depth research into canine and feline nutrition, and states that:


"If given free access to food, cats will eat between 12 and 20 meals a day, evenly spread out over the 24-hour light-dark cycle. It goes against the nature of the cat to force it to eat only one meal a day."


Thus asking a cat to eat only once or twice a day is stressful for most cats (which is a risk factor for FLUTD); and in fact it is a fallacy that frequent eating causes significant post-prandial alkalosis: it is actually smaller after a small meal than after a large one, so smaller meals seem more appropriate to me. Pet Education has more information on this.


Reduce Stress

FLUTD appears to occur more frequently in cats who are stressed. It is more common in indoor only cats, for whom environmental enrichment is recommended. One study, A study of environmental and behavioural factors that may be associated with feline idiopathic cystitis (2004) Cameron ME, Casey RA, Bradshaw JW, Waran NK, Gunn-Moore DA Journal of Small Animal Practice 45(3) pp 144-7, found that obesity and stress appear to be factors in the development of FLUTD but states that the biggest risk factor appears to be living with another cat with whom there is conflict. The Feline Introductions page may help with this.


Grow Older

One good thing about FLUTD is that, according to Harpsie's nephrologist, cats tend to grow out of it as they age. This seemed to be true of Harpsie: he had just turned 6 when he first blocked, and was 8 when he blocked again (he did have other FLUTD problems inbetween the blockages), but he never blocked again after that. Of course, older cats may be more prone to forming calcium oxalate stones. Whilst this didn't happen to Harpsie, he did develop kidney infections instead (he also had PKD, which predisposes a cat to kidney infections).  




Pet Education has very helpful information about FLUTD.

Mar Vista Vet has excellent and detailed information on FLUTD.

Feline Advisory Bureau - an overview by the UK feline charity.

Long Beach Animal Hospital - detailed and helpful information. 

Washington State University College of Veterinary Medicine - helpful information, but quite technical.

The Winn Feline Foundation has a good overview of FLUTD.

The Winn Feline Foundation also discusses bladder stones and urinary obstructions.

Feline lower urinary tract disease (2006) Sparkes AH Presentation to the 31st World Small Animal Veterinary Association World Congress has a brief overview of FLUTD.

FLUTD List is a support group for people whose cats have FLUTD. 

Cats with FLUTD List is another support list for people dealing with this problem.


Harpsie's Experiences

Harpsie first blocked less than a month after his sixth birthday. We were going out to a committee meeting one evening, and I saw him go to his litter tray as I began to get ready. When I went downstairs I discovered he had gone into the garden and was squatting in a flower bed. This was unusual for him but not unknown. We had never heard of urinary tract blockages (I wish vets would tell people more about the symptoms and risks before the problem ever arises!), so we thought he was simply constipated. I planned to give him some constipation meds and see how he was - it simply never occurred to me that this was an emergency.


I am not a morning person, so I used to get up at the last possible minute, having prepared everything I needed the night before, and run out the door to catch my train (I had a long commute and used to leave home very early each morning). Fortunately for Harpsie and for us, as it happened I actually had a blood test booked at the hospital for that day, so I was not in such a rush as usual. My husband told me Harpsie seemed a bit subdued, so I went to Harpsie, who would not make eye contact. I picked him up and he howled - he was clearly uncomfortable. I called the vet, and was given an appointment for 9.30 a.m.


I went for my blood test, then Harpsie and I went to the vet appointment. I still had no idea how serious things were. Within seconds the vet realised Harpsie was blocked. She told me she would have to admit him and perform emergency surgery. She warned me Harpsie could die. I was devastated, and so worried.


Later that day I spoke to Harpsie's breeder, who told me Harpsie's father had also blocked in the past! Why didn't she tell me this earlier?


Harpsie survived the surgery, which entails putting a catheter in the urethra under general anaesthesia to try to clear the blockage. He was supposed to stay at the vet's for four days, with the catheter in place for two of those days, until the vet was sure he was out of the woods and could urinate by himself. But the vet called me after one night and told me Harpsie was in such a state he would be better off at home. He was refusing to eat for them, and he was also terrified: when I went to collect him, I had to go to the cage and remove him myself using gauntlets, and he tried to bite me several times (and they told me he was still calmer than he had been with them!). It was from this time that Harpsie began exhibiting fear aggression at the vet's - I assume because the blockage was so painful and frightening for him. 


Harpsie was glad to be home but he was still not at all well. But eventually he was prepared to eat for me. His first evening home he spent lying on my knee. He still had the catheter in place, so pee could dribble out, but it was not a large amount and was easily managed by a towel on my knee. I was so relieved that he had survived despite our delay in getting him treatment, but even now I still shudder when I remember how close we came to losing him - the vet told me afterwards she had thought she would not be able to save him. The catheter was removed the next day, and Harpsie was able to pee unaided, thank goodness. 


Harpsie was supposed to eat the Hill's s/d, which fortunately he liked. After a few weeks we switched him to the maintenance diet, Hill's c/d. He ate this happily for about six months, then he began to get bored with it. I was firm with him though, and encouraged him to eat it. But he gradually stopped eating, so after speaking to my vet, we allowed Harpsie to eat normal "urinary tract friendly" commercial food, and gave him daily urine acidifying tables (DL-methionine).


Unfortunately these tablets can have side effects if used longer term, so we took Harpsie off them after about a year. Not too long afterwards, he blocked again - this was about two years after his first blockage. He only blocked 70% on this occasion, because we realised something was going on quite quickly (he was squatting in his litter tray but nothing was coming out) and got him into the vet as an emergency at midnight. On this occasion he did not need catheterising under general anaesthesia, IV fluids managed to flush him out.


We watched Harpsie like a hawk, but in fact he never blocked again. He did have urinary tract problems regularly, but eventually he began developing kidney infections (he also had PKD, which predisposes a cat to kidney infections), rather than FLUTD. This brought its own set of problems for us to learn about.







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This page last updated: 26 March 2008


Links on this page last checked: 2 February 2008


Copyright Harpsie's Site 2005-2008. All rights reserved.






I have tried very hard to ensure that the information provided in this website is accurate, but I am NOT a vet, just an ordinary person who cared for Harpsie with the help of qualified vets. This website is for educational purposes only, and is not intended to be used to diagnose or treat any cat. Before trying any of the treatments described herein, you MUST consult a qualified veterinarian and obtain professional advice on the correct regimen for your cat and his or her particular requirements; and you should only use any treatments described here with the full knowledge and approval of your vet. No responsibility can be accepted.


If your cat appears to be in pain or distress, do not waste time on the internet, contact your vet immediately.



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