Urinary Tract 'Stones' & Cystitis in Cats and Dogs

Dietary factors play a major role in the development of kidney stones that can block the urinary tract in cats and dogs and cause great discomfort, even death. These ‘stones’ or uroliths, (also called calculi, or ‘sand’ when in fine particles/crystals) have various chemical compositions, the most common being composed of calcium oxalate or of ‘struvite’—a composite of magnesium, ammonium and phosphate.

Aside from the fact that certain breeds are more susceptible, there are several co-factors that have also been identified in the increasing incidence of kidney stones in children. These include not drinking sufficient fluids (water) which is a major problem when cats are fed only dry food. Then the urine becomes more concentrated (hypersaturated) which can trigger bladder inflammation. Bladder inflammation can also be associated with bacterial infection (notably Staphylococcus and Proteus), especially in female animals. The bacteria convert urea in the urine into ammonia that inflames the bladder wall and makes the urine alkaline, creating an ideal environment for struvite crystals to form often around a core of bacteria or inflammatory material from the wall of the bladder.

When dogs and cats are fed high cereal diets their urine becomes abnormally alkaline (it is more acidic on a biologically appropriate meat-based diet). Such diets are another co-factor in the development of struvite crystals or calculi. So the best prevention is obvious.

In order to avoid this problem but not reduce the cereal content of their formulas, pet food manufacturers, who initially blamed high ‘ash’ content of their foods and came out with low magnesium diets that proved to be of no benefit, now acidify the formulas.

Acidification is a co-factor in the development of increasingly prevalent oxalate crystals in cats and dogs. Pets with oxalate crystals are often given potassium citrate to make the urine more alkaline so as to help prevent oxalate crystal formation. Adding extra salt to the pet food to make animals drink more water to control struvite crystal formation actually encourages the formation of oxalate crystals, a problem seen in children where the sodium in the salt triggers more calcium excretion by the kidneys. The excess calcium combines with oxalates present in many foods, to form calcium oxalate crystals. Soy products (a cheap source of protein used widely by pet food manufacturers) are high in oxalates and probably represent yet another co-factor in the genesis of urinary tract blockage and much suffering and expense to pet owners.


The feline urologic syndrome, that involves inflammation, and possible infection, and painful mineral crystal and stone formation in the urinary tract, and often the development of mucous plugs in the urethra, is a widespread problem in cats today.

It is a major reason why cats are euthanized, or are put outdoors for the day or night because they become house-soilers, urinating in the home outside of their litter boxes. The major reason why cats develop this distressing condition is because they are fed a dry food diet too high in cereals that makes their urine too alkaline, which encourages the formation of urinary calculi or crystals. The lack of moisture in the cat’s diet can lead to highly concentrated urine that is extremely harmful to the lining of the bladder.

Symptoms of cystitis include straining to urinate, frequent, often frantic licking of the hind end, and great difficulty in urinating, blood in the urine, urinary tract obstruction and inability to urinate at all, (a painful emergency), loud crying, and voiding at the care-taker’s feet as a clear display of distress.

This serious, treatable condition is to be distinguished from cats’ aversion to using the litter box for such reasons as: it is not being cleaned out daily by the care-taker; the cat does not like the type of litter; the box is not in a quiet, low-traffic, easily accessed part of the house; the box is enclosed under a hood, and the interior becomes ammoniated; the cat has a pain-associated aversion to using the litter box because of constipation, impacted or infected anal glands, arthritis, especially spinal, in older cats, and diseases of the urinary tract.

If crystals/urinary calculi are involved in the cystitis, it is important to determine what type they are chemically. With most types, acidifying the urine with Vitamin C or capsules of cranberry can help. Uva ursi or Bearberry can be a valuable anti-microbial and anti-inflammatory herbal treatment for cystitis, but it tends to make the urine alkaline, which is not desirable if a cat has struvite crystals in the urine. But an overly acidified, artificial diet can lead to calcium oxalate crystal/urolith formation in the urine, so maintaining an optimal acid-base balance in the cat’s diet, and normally slightly acidic urine, is essential. Giving appropriate probiotics may help when there are oxalate crystals, and in cases of uremia, and bacterial infection of the urinary bladder and tract.

Encouraging the cat to drink more water, as by flavoring with milk, tuna juice or unsalted beef or chicken broth, and not feeding an all-dry type commercial cat food are additional steps to take. Diuretic herbs like parsley and dandelion help keep the urinary tract flushed out, but increasing the cat’s fluid intake, as with flavored water and moist, canned or home-prepared foods, is important. No cereals and more raw or lightly cooked meat to increase the acidity of the urine is advisable in many cases, unless they have calcium oxalate crystals in their urine.

Cats with cystitis and incontinence may have an underlying food allergy and some have made spontaneous recoveries when all corn was eliminated from their diets—a common ingredient in many cat foods.

Cats with cystitis often need antibiotics because of underlying infection. Diabetic cats and those on long-term steroids, often develop bacterial cystitis because of lowered immunity. Incontinent cats should be checked for these problems.

Changing the type of litter to a non-mineral/clay base, like newspaper or corn pellets, may also help.

Emotional stress, as well as an all-dry diet, is a major aspect of feline cystitis/urologic syndrome. Environmental enrichment, as with perches and climbing posts; a cat ‘condo;’ safe places to hide; identifying and resolving conflict between cats in the same home; regular play and grooming; providing an extra litter box, and putting out extra food and water bowls located in a quiet place were cats will not be startled or compete with each other are all helpful preventive measures. Treatment with an analgesic like Butorphanol, or with Valium or Valerian, that have antispasmodic properties as well as being anxiety-alleviating, has helped many cats during the first 5-10 days of treatment.


Am J Vet Res. 2004 Feb;65(2):138-42.

Evaluation of effects of dietary carbohydrate on formation of struvite crystals in urine and macromineral balance in clinically normal cats by Funaba M, Uchiyama A, Takahashi K, Kaneko M, Yamamoto H, Namikawa K, Iriki T, Hatano Y, Abe M.

Laboratory of Nutrition, School of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Sagamihara 229-8501, Japan.


Urine volume was lower in the starch group and fiber group in study 1, whereas no differences were detected among the groups in study 2. Urinary pH and struvite activity product were higher in the starch group in both studies, and the fiber group also had higher struvite activity product in study 2. In both studies, urinary concentrations of HCl-insoluble sediment were higher in the starch group and fiber group. In the fiber group, a net loss of body calcium, phosphorus, and magnesium was detected in study 2.


Starch and fiber in diets potentially stimulate formation of struvite crystals. Hence, reducing dietary carbohydrate is desirable to prevent struvite urolith formation. In addition, a net loss of body calcium, phosphorus, and magnesium during feeding of the fiber diet suggests that dietary inclusion of insoluble fiber could increase macromineral requirements of cats.

Also, these acidifying diets, which are so often prescribed, may end up promoting calcium oxalate stones and hypokalemia.

Many prescription diets, as detailed in the book that I co-authored with two other veterinarians, Not Fit for a Dog: The Truth About Manufactured Cat and Dog Food, are not only costly and contain dubious ingredients but are often highly unpalatable. A good source for more palatable, veterinary-formulated special diets is the company called Balace IT. Website www.Secure.balanceit.com Cats and dogs seem more prone to develop urinary crystals/calculi/stones when fed dry kibble, while moist canned, rehydrated freeze-dried and thawed frozen food formulations mean less concentrated urine, bladder inflammation and bacterial infection and likelihood of struvite ( magnesium ammonium phosphate) or calcium oxalate crystals forming in the urine. Males suffer more when their urethras become blocked and emergency surgery is needed. Some manufactured pet foods are acidified to help prevent struvite crystal formation which may then lead to oxalate crystal formation, the prevention of which some veterinary nutritionists contend calls for a diet of low protein, low oxalate and sodium but high cereal content to make the urine more alkaline. Potassium citrate ( 40-70 mg/kg) in the food twice daily can help normalize the urine acidity/alkalinity.

But in my opinion the best preventive is to ensure a high moisture content in a balanced, biologically appropriate diet and making sure the animal is always well hydrated. cats especially may not maintain optimal hydration so adding a little chicken bullion to their drinking water can help encourage adequate water intake: same for dogs prone to oxalate crystals.

This seems to have a genetic basis, being seen frequently in breeds like the Lhasa apso, Yorkshire terrier, Miniature and Standard Schnauzers, Bichon frize, Shi tzu and Miniature poodle. A metabolic anomaly causing elevated calcium in the blood may play a role in oxalate crystal formation.