top of page
HG Cystolith1.JPG

Bladder Stones in a Cat - One of the Common Causes of Cystitis 

Cystitis is inflammation of the urinary bladder.


This is a common condition in cats and causes painful urination. The signs that people notice most commonly are frequent attempts to urinate, small amounts of urine produced at a time, urinating outside the litter box, and blood in the urine.

There are three common causes for this painful, bloody urination:

North County Cat Hospital

Cystitis in Cats

Home / About Cats  / Diseases / Cystitis 


This page describes the three most common causes of of cystitis in cats. There are other, less common causes.

(This page uses three separate columns to organize information and is easier to understand when viewed from a computer screen than from a smart phone.)

Idiopathic Cystitis

This is the most common cause of cystitis in cats. We don't know why cats get this but it is not due to bacterial infection and antibiotics are not helpful. A lot of cats will recover from this disease with no treatment. This causes confusion because if a cat with this disease is given antibiotics and then gets better, people incorrectly think that the improvement was due to the antibiotics.

Alternate names:

FIC - Feline Idiopathic Cystitis

FIC - Feline Interstitial Cystitis

UTI - Urinary Tract Inflammation 

iFLUTD - Idiopathic Feline Urinary Tract Disease

FLUTD - Feline Lower Urinary Tract Disease

FUS - Feline Urologic Syndrome

Bladder Stones

Bladder stones are a less common cause of cystitis in cats. Some stones can be dissolved with diet. Some require surgery to remove.

Alternate names:

Urinary Stones




Bladder stones in a cat.

Bladder Stones in a Cat - One of the Common Causes of Cystitis 

Bladder Infection

Bacterial infection of the bladder is common in older cats but is almost always associated with an underlying condition - either diabetes or kidney disease. Because of this, it usually needs to be treated with an effective antibiotic for at least six weeks.

Alternate names:

UTI - Urinary Tract Infection


"UTI" is sometimes used to mean urinary tract inflammation and sometimes used to mean urinary tract infection

Signs of Cystitis:

The signs for all causes of cystitis are similar. They can't be distinguished by clinical signs alone. 


Humans with cystitis describe it as being very painful and we are confident that the same is true in cats. Cats show pain in a number of ways including hiding, not eating, and vocalizing. Frequently the signs of pain are so subtle that humans don't know their cat is in pain.

Frequent Urination:

With cystitis, the nerve endings in the bladder are stimulated, making it feel to the cat as though they have to urinate, even when the bladder is empty. Humans will see the cat squatting as though to urinate with nothing coming out. This is problematic in that the exact same thing is seen when a cat has a urinary obstruction. They squat to urinate and no urine comes out.

House Soiling:

For reasons that are variable and not fully understood, some cats will urinate outside the litter box when they have cystitis.

Photo by Jae Park on Unsplash Bandana ca

Most cats won't tell us  when they are in pain.

Cystitis Can Be Life-Threatening

Cystitis can potentially lead to urinary tract obstruction which is very painful and can cause death within hours. Obstructed (blocked) cats are typically not eating, very vocal, and very sick. 

Idiopathic Cystitis - 
Obstruction Risk

Male cats: High

Female Cats: Low

Bladder Stones -
Obstruction Risk

Male Cats: Moderate

Female Cats Moderate

Infection - 
Obstruction Risk

Male Cats: Low

Female Cats: Low


Discussing cystitis in cats is confusing. This is because words are used differently by different people. This is a list of our use of the words. Beware that other sources may use other definitions.

Crystaluria: Crystals in the urine. 

Cystitis: Inflammation of the urinary bladder regardless of cause.

Dysuria: Difficult or painful urination. This may manifest as squatting to urinate for long periods, making frequent trips to the litter box, urinating outside of the litter box, howling, or a number of other ways.

Hematuria: Blood in the urine. Sometimes the urine still looks yellow and the blood can only be detected microscopically or with chemical tests. Sometimes it looks like pure blood.

House soiling: Urinating or defecating in the house, outside of the litter box. Some veterinarians use the term periuria or inappropriate urination.

Idiopathic: A medical condition with a cause that has not yet been established in the medical literature. 

Stranguria: Straining to urinate. Since cats don't usually make a face or an odd noise when they strain, a lot of times humans don't recognize what they are doing to be straining.

Stress: Psychological stress. This is an internal reaction to usually external stimuli. Anything that causes a cat to become upset, including medicating them, can cause stress.

Urethral Spasm: Inappropriate and painful contraction of the muscle of the bladder / urethral sphincter. Urethral spasms can prevent a cat from being able to urinate or they may cause an unsteady or intermittent stream of urine.

Urinary Obstruction: Anything that obstructs a cat's urethra so that they can't urinate. This is sometimes a "plug" of debris (crystals, blood, etc.) and it is sometimes a urethral spasm. Urinary obstructions are life threatening.  

Causes of Idiopathic Cystitis

Interstitial cystitis in cats is an idiopathic condition - meaning we don't know what causes it. We do know that stress and obesity are often predisposing factors.

Most cases of FIC resolve without treatment. This can create a lot of confusion in understanding the underlying cause. For example, if a cat with FIC is put on a special diet and gets better, a lot of people conclude that the old diet caused the FIC and that the new diet helped when really, the cat just had a transient, self limiting cystitis. Likewise, if a cat with FIC is put on antibiotics and gets better, it doesn't mean that there was an infection or that the antibiotics were in any way helpful. 

Causes of Bladder Stones

Diets high in certain minerals and low in water (dry food) can predispose a cat to bladder stones. The pH of the urine can be a factor. There are some metabolic disease that will cause some cats to develop stones.

A lot of times we don't really know why one cat gets a stone, and another doesn't.

Causes of Bladder Infection

Bladder infections in cats are almost always due to a bacteria. Because cats normally have very concentrated urine and effective immune mechanisms, it is very rare for them to have a bladder infection unless there are underlying conditions that allow bacteria to grow, most commonly kidney disease and diabetes.

Infection is a common cause of cystitis in cats with kidney disease or diabetes. Infection is rare in cats without one of these underlying diseases. Of young cats with cystitis who don't have kidney disease or diabetes, approximately 3% have an infection.  That means that about 97% of young, otherwise healthy, cats who are showing signs of dysuria (difficulty in urinating) don't have an infection and don't benefit from antibiotics. 

Our experience is that most young cats who have been diagnosed with a "UTI" actually had idiopathic cystitis that is not a true infection.

Causes of Cystitis 
Dry Cat Food
Dry Food.jpg

Dry cat food may predispose a cat to any of the common causes of cystitis.

We usually only see idiopathic cystitis and bladder stones in cats who are eating dry food.

We usually only see diabetes in cats who are eating carbohydrates and diabetes can predispose a cat to bladder infection.

Things that Probably Don't Cause Cystitis in Cats.

There are a a number of things that have been incorrectly described as causing idiopathic cystitis in cats.


Crystals commonly form in a cat's urine when:

  • The urine is concentrated (e.g., from a diet low in moisture / water)

  • The pH of the urine is high (e.g., from a diet high in carbohydrates)

  • The kidneys secrete high levels of minerals (e.g., from a diet high in ash)

  • There is blood in the urine (e.g., when a cat has cystitis)

  • The urine stays in the bladder for prolonged periods (e.g., when a cat is obstructed)

  • The temperature of the urine decreases (i.e., crystals will grow after the urine sample is taken from the cat)

Crystals almost never cause cystitis but are often caused by cystitis.

Under the microscope the crystals look sharp and we used to think that the crystals caused the bleeding. Most experts now agree that crystals don't cause inflammation and bleeding. Inflammation and bleeding cause crystals.

We see a lot of cats with crystals in the urine who have no sign of cystitis.

We don't want crystals in the urine because:

  • They can be a sign of a problem (e.g., lack of water intake or too much carbohydrate in the diet)

  • They may predispose a cat to forming stones in the bladder and kidneys.

  • A male cat with cystitis is more likely to get a urinary obstruction if he also has crystals

Ash in the Diet

"Ash" is the component of food that is left over when the food is burned (i.e., it is the same as ashes).  It is composed of minerals, such as phosphorus and calcium. We used to try to limit ash in the diet because it may be associated with crystals. Ash is no longer considered a factor in causing cystitis.


Neutering predisposes cats to becoming obese and obesity predisposes cats to getting idiopathic cystitis. Other than that, there is probably no relationship between neutering and FIC.

Urinary Obstruction

There was a study that showed that some cats with cystitis have urethral obstruction and the study suggested that the obstructions were the cause of the cystitis. Most experts agree that this is almost never the case: the cystitis is the cause of the obstructions, not the other way around.

Treatments for Cystitis 
Treating Idiopathic Cystitis

There is no treatment that is proven to resolve FIC.

Hill's Prescription Diet c/d Multicare Urinary Stress was shown to decrease the incidence of recurrence of FIC compared to another diet but that diet was one that was created specifically for the study. 

When we see a case of FIC, we usually recommend:

Short term treatment to:

  • Resolve pain

  • Resolve urethral spasms

  • Dilute the urine 

  • Reduce stress

Long term treatment to:

  • Normalize weight

  • Resolve stess

  • Dilute the urine

Treating Bladder Stones

Before treating for bladder stones, it is important to look for and attempt to resolve underlying diseases that might be contributing to the formation of the stones.

For most stones, we attempt to dissolve them medically (through diet). If that doesn't work, then removal through urohydropropulsion or surgery is used.

Lithotripsy is not typically used  in cats.

No Dry Food.jpg

We rarely see FIC or bladder stones develop in cats who are on high quality canned food.

Treating Bladder Infection

Bladder infections are treated with antibiotics.


When treating for bladder infection it is important to:

  • Look for the underlying cause and address that.

  • Confirm (by culture) that there is a true infection - not just cystitis.

  • Know (by culture) what antibiotic will be effective against the bacteria.

  • Treat with the appropriate antibiotic consistently for an appropriate period of time

Things that Probably Don't Help Cats with Cystitis.

There are a a number of things that have been used to treat cystitis in cats that probably don't work.

Prescription Diets

There is no scientific evidence that supports the use of prescription diets over high protein, over-the-counter canned cat food in the treatment of FIC in cats. They may help with cystitis related to stones.


Cranberries are helpful in people to treat infection. They are in a lot of things to treat cystitis in cats. Studies indicate that they don't help. The vitamin C in cranberries may predispose cats to certain bladder stones. So they may actually increase the incidence of cystitis.

Perineal Urethrostomy Surgery

"PU" surgery is sometimes used to prevent male cats with idiopathic cystitis from becoming obstructed. This surgery may prevent obstruction but does not prevent cystitis. It can predispose a cat to urinary tract infections so I almost never recommend it.


In humans, interstitial cystitis is treated with Elmiron, which is a drug that is similar to Adequan. Because of this, some veterinarians recommend Adequan for cats with FIC. I'm skeptical that it is helpful.

Steroids or NSAIDs

We used to try to treat FIC with corticosteroids and other anti-inflammatories, but because the inflammation involved with FIC is different than most inflammatory conditions, they don't work.

Any Of the Three Hundred OTC Products that Claim to Work

There is just no evidence that any of these are helpful.

bottom of page