Kidney stones form in cats for a few different reasons. The different causes ultimately predict which type of nephro (kidney) + lith (stone) is most likely to form. And the type of stone affects what treatments might help. Cats with small kidney stones really may have no signs at all. Kidney stones may show up on x-rays of the belly that are being taken for unrelated reasons, as a so called “incidental” finding. Since kidney stones in cats don’t seem painful, why should we worry about them?
A kidney stone that allows normal urine flow out may be one that your vet watches closely, but ultimately leaves untreated. However, if the stone gets very large, or if little pieces break off and lodge in the ureter (the long narrow tube that connects each kidney to the urinary bladder), it likely becomes very painful. Kidney colic—signaled by abdominal pain, malaise and even vomiting—may result; the kidney may swell and be damaged. If this should happen simultaneously to each kidney, and the blockage persists, your kitty will likely become critically ill from the disrupted flow of urine. If you think your cat’s abdomen is painful, or his urinations change in any way, please contact your veterinarian right away. A urinary obstruction is a life threatening emergency that must be treated!
Signs of kidney stones in cats
The signs and symptoms of kidney stones could include:
- Abdominal discomfort
- Kidney pain
- Blood in the urine (hematuria)
- Altered urine production (increased or decreased)
- Poor appetite
- Weight loss
Diagnosis of kidney stones in cats
Most stones usually show up readily on plain radiographs, but small stones may be hidden behind intestinal contents. Another reason that simple x-rays may not give enough information is because certain stones just don’t show up well. An example would be a urate stone, which might occur as a result of liver disease. Once a stone has been diagnosed, your vet will want to do some tests to help with predicting the stone type. Tests are needed also to assess what impact the stone(s) may be having on your cat’s kidney health, and whether other conditions may be present that might increase the risk of stones. Testing may include:
- Complete blood count (CBC)
- Blood chemistry with electrolytes — Testing for evidence of kidney disease and risk factors for stone formation
- Urinalysis— The urine quality may predict kidney disease and help identify bacterial infection or crystals that may help predict stone type
- Urine culture with susceptibility— To identify bacterial infection and the best antibiotic choice(s)
- Abdominal radiographs (x-rays)— To examine the size and shape of the kidneys and look for urinary stones
- Systemic blood pressure— To identify an important complication of kidney disease
- Abdominal ultrasound— This will help verify the location of any stones and the suspected degree of any obstruction
- Contrast radiography— Dye studies may be needed to confirm blockage and help to show the contribution that each kidney makes to urine production.
Causes and types of kidney stones in cats
Most cats affected by stones are middle aged or older1.
Metabolic kidney stones (those formed due to a blood or urinary imbalance) are much more common in cats than infection-based stones1. Your veterinarian will determine treatment based on the kind of stone and what it’s made of.
Treatment of kidney stones in cats
A reason to treat kidney stones is bacterial urinary infections that recur or cannot be cleared. Veterinarians often struggle to determine whether the stone or the infection comes first, but sometimes eliminating a kidney stone is needed to help resolve the infection.
Again, with some types of urinary stones, your veterinarian may want to treat conservatively, with a combination of antibiotics, diet and plenty of fluids. Dissolving kidney stones completely often takes months, but any early reduction in size is great news.
It’s likely that your kitty with a kidney stone will not need more specific treatment to remove it. But it’s good to be prepared, and to understand what’s involved if the situation changes. Medical efforts to dissolve feline kidney stones are usually safer than surgery, but won’t work for most stones. Since most feline kidney stones won’t dissolve, plans for treatment can be challenging for your cat’s veterinary team. Skilled surgery is widely available to remove kidney stones, but does risk permanently damaging the affected kidney, even if the surgery goes smoothly.
Special techniques to break up a stone (lithotripsy for example) are not usually recommended for cats because the stone fragments tend to lodge in their narrow ureters2. Fortunately, veterinary specialists are continuing to find better treatments of cat kidney stones by applying advanced techniques, commonly used in people, to our feline friends. For some cats, specialists may recommend treatment with an endoscope (a small device with a light attached). For emergency situations, when the ureters are blocked, they might recommend life- saving bypass techniques that re-route urine around the blocked ureters3. It’s always fair to ask your doctor if surgery is the only option, or if there might be a cutting edge technology to try, instead of surgical cutting.
Monitoring and management of kidney stones in cats
If your vet suspects oxalate kidney stones, she may suggest a special diet and some medications to reduce or slow stone growth, with a big emphasis on increasing kitty’s water intake. By encouraging your cat to drink more, or to take extra water in the form of canned food, the urine should be more dilute. The goal here is to reduce the amount of mineral available to add to a stone.
Many special diets are available to prevent or manage urinary stones, but finding the best fit for your cat could take some trial and error. Your vet will also want to balance the dietary needs of any other illness that kitty has, such as kidney disease, diabetes or gastrointestinal disease. If an underlying cause for stones is suspected, then resolving that primary problem will be a key part of any plan.
Even if the stones don’t seem to be causing complications now, your vet will likely ask you to agree to regular monitoring of blood and urine tests for the foreseeable future. It’s important to know that any prevention strategy is working, and to show that the stones are not growing or causing complications. Likely your vet will recommend repeating radiographs (x-rays) or ultrasound studies periodically. If the stones have been removed, monitoring for any recurrence will be critical to keeping your kitty healthy. You and your veterinarian can map out the monitoring schedule that best matches your cat’s condition.
If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.
- Jessica E Markovich and Mary Anna Labato, Medical Management of Nephroliths and Ureteroliths in JD Bonagura and DC Twedt ed Kirk’s Current Veterinary Therapy XV, Saunders Elsevier, St. Louis, 2014 PP 892-896
- (3tate of the Art: Nephroliths and Ureteroliths - A New Stone Age World Small Animal Veterinary Association World Congress Proceedings, 2013 Larry G. Adams, DVM, PhD, DACVIM (SAIM) Purdue University, West Lafayette, IN, USA
- Proceedings: Diagnosis and Management of Feline Ureteral Obstructions: Past Present and Future ACVIM 2014 Allyson Berent DVM, DACIM (SAIM) New York NY
Diagnosing Struvite Crystals
If you notice any of the symptoms above, its best to contact your veterinarian immediately. At your veterinary visit, your vet will perform an exam and diagnostics to rule out the known causes of struvite crystals and stones and form a diagnosis.
- History: Your veterinarian with the help of the veterinary technician will obtain a history on your cat. This will include your cats’ behavior, including any changes to the environment, cat’s routine and schedule, and any other symptoms you have observed at home.
- Physical Exam: Your veterinarian will perform a physical exam of your pet
- Bloodwork and Urinalysis: By obtaining and running bloodwork and a urinalysis, your vet will be able to see how your cat’s internal organs are functioning as well as check for dehydration, bladder inflammation, and infection.
- Urine Culture and Susceptibility: A urinalysis sample should ideally be obtained via a cystocentesis which is a procedure where a needle is placed into the urinary bladder through the abdominal wall and a sample of urine is removed. A urine culture test is a method of identifying the specific bacteria that may be causing a urinary tract infection. It involves placing a urine sample on a special medium, incubating the sample so the bacteria can grow, and then identifying the bacteria. A second test (a sensitivity test) is usually conducted to determine the most effective antibiotics to use against the bacteria involved.
- X-Rays and Ultrasound: These are done to assess if the bladder appears abnormal or contains bladder stones. Radiographs are the most effective way to diagnose bladder stones, because most bladder stones (including struvites) are visible on radiographs. On radiographs, struvite stones typically look like smooth rocks or pebbles within the bladder. Ultrasound may also be used to visualize bladder stones.
Types of kidney stones in cats
There are various forms of kidney disease in cats, but kidney stones (known as a calculus) will not necessarily cause permanent damage. They are, however, incredibly painful and can lead to complications if they are accompanied by a bacterial infection which can lead to sepsis  . The ‘stones’ themselves are actually crystals formed by different chemicals in the urinary tract of the cat and are a part of a larger group of diseases known as Feline Lower Urinary Tract Disease (FLUTD).
Cats can produce kidney stones which are expelled naturally by the body. They may form in the kidney and are then passed on to the bladder where they are expelled through urination. The calculus causes problems when it is too large to pass through the urinary tract. If they are large enough they will cause partial or total obstruction which is both painful and dangerous.
During the formation of the deposits, the pH value of the urine is very important since it will influence how alkaline or acidic is their urine. Similarly, the stones are classified according to their composition. They will depend on the diet of the individual cat, but the two most common are:
- Struvite stones: the most common type of feline kidney calculi, they are formed by ammonium phosphate and magnesium in urine with high alkalinity. This occurs most commonly after a urinary tract infection, since crystals can form around the bacteria. They can also occur in younger cats.
- Calcium oxalate stones: formed in acidic urine, they occur due to a high concentration of calcium in the urine.
Ways to Eliminate Kidney Stones in Cats
Kidney stones in cats are the result of the modern way of life. Natural cat health, or the ways of the wild, prevents the formation of kidney stones. Let’s look at why and then measures you can take to prevent or eliminate them without expensive and invasive surgery.
Kidney stones in cats, as in everyone, are insoluble mineral salts that accumulate over time. They are hard and of variable size. Without help, they are extremely painful to pass.
The symptoms a cat can exhibit, indicating kidney stones, include frequent urination, straining to urinate, passing only small amounts of urine and sometimes blood (not always visible) in the urine. Serious cases can lead to vomiting, a loss of appetite, weakness, lethargy and depression.
Cats try to tell us when something is amiss by behaving out of character. They may urinate in unusual places, a sure sign that something is upsetting them. Cats are fastidiously clean, so you need to look beyond your own displeasure when this happens.
Veterinary diagnosis includes X-rays, urine test and ultrasound. As bladder infections invariably accompany any renal disturbance, your cat will inevitably be prescribed antibiotics. However, bacteria are not the cause of the kidney stones. They are merely opportunistic feeders when the health of your cat is down. Antibiotics are liver toxic and lower the immune system, so they don’t help your cat help herself.
The main cause of kidney stones is an unhealthy diet. The vast majority of commercial cat food provides your cat with an unhealthy diet, even the expensive ones from your veterinarian.
So the best way to prevent this unhappy and painful problem occurring, you need to feed your cat a quality, natural diet. This will also dissolve kidney stones that are not currently causing any great problem. However, well advanced cases may need immediate treatment. Homeopathic treatment can provide instant relief and help pass the stones without incident.
Prevent kidney stones in cats forming, and keep your cat healthy overall, by feeding your cat according to natural cat health.
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Kidney stones don't typically present symptoms until they grow large, irritating the kidney ducts and potentially causing a serious infection or obstruction. Male cats and domestic Shorthairs are more likely to develop kidney stones than females and other breeds of cats.
The kidneys are responsible for filtering the blood, removing wastes such as mineral salts, urea, and toxins, and excreting these filtered wastes with water in the form of urine. Some of these wastes that are normally excreted by the kidneys aren't completely soluble and remain in the kidneys, forming crystals or renal calculi. Over time, these crystals can form stones, known as nephroliths, and cause a condition known as nephrolithiasis.
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