Updated: May 4, 2021
Sometimes cats and dogs experience difficulty in passing urine. The difficulty can be expressed either through:-
Painful or difficult urination (dysuria),
Blood appearing in urine (haematuria),
Increased frequency of urination (pollakiuria),
Dogs leaving puddles in the house and cats in and out of the litter box with increased frequency,
Painful, frequent urination of small volumes that are expelled slowly only by straining (stranguria),
Increase in thirst levels (polydipsia),
Non-passage of urine (anuria/oliguria),
Excessive licking of private parts,
Lack of appetite and
It could be kidney or bladder stones.
Kidney or Bladder stones (uroliths), what are they?
Dogs and cats can develop stones anywhere in the urinary tract system. They can develop in the kidney, ureter, bladder, or urethra, referred to as nephroliths, ureteroliths, urocystoliths, and urethroliths, respectively. These stones are formed in many different shapes and sizes. Bladder and kidney stones are toughened deposits of minerals found in urine. The minerals involved include struvite, calcium oxalate, cystine, urate and silica stones.
1. Struvite stones
These contain magnesium ammonium phosphate in both dogs and cats. They may also contain calcium phosphate or calcium carbonate. High dietary intake of protein and minerals encourages urine to be supersaturated. Urinary tract infection (UTI) is a predisposing factor in the formation of this stone. About 50% of uroliths (bladder stones) are struvites.
2. Calcium oxalate stones
Calcium oxalate stones are associated with the increased use of acidifying diets; changes in dietary content of calcium, magnesium, phosphorus, and oxalate; more sedentary lifestyles; decreased water intake; small breeds that are more prone to developing calcium oxalate stones; increased incidence of overweight dogs; and/or dogs living to more advanced ages. About 70% of canine and feline oxalate sones are from males which is related to an increase in the hepatic production of oxalate mediated by testosterone. Conversely, estrogens in female dogs may increase the urinary excretion of citrate, which facilitates the formation of soluble calcium citrate. Abou30% of uroliths (bladder stones) are calcium oxalate.
3. Cystine stones
Cysteine is found in most high-protein foods, including pork, poultry, eggs, and dairy products, as well as oats and wheat germ. Cystine is absorbed by the small intestine, freely filtered, and then reabsorbed by an active process in the kidneys. Decreased reabsorption of cystine results in cystinuria (cystine in urine), a predisposing and required factor for—but not the sole cause of—cystine stones. Not all dogs have cystine in uroliths or even have cystine crystals in their urine; the exact mechanism of cystine stones formation is unknown, but there is a genetic condition that increases cystine in the urine. About 1% of uroliths (bladder stones) are cysteine.
4. Urate stones
Ammonium urate bladder stones (urate stones) are a type of bladder stones in dogs and cats that occur as a result of a genetic deficiency in the way uric acid is metabolized in the body. Urate stones are the third most common urolith type in dogs and cats. In dalmatians, a recessive gene that causes a defect in hepatic uric acid metabolism leads to increased urinary urate excretion. This trait in the dalmatians s responsible for their predisposition to urate stones. In other dog breeds and in cats, urate stones are predominantly associated with liver disease. Idiopathic urate uroliths may occur in animals without liver disease. Urate stones are amenable to medical dissolution. Approximately 8% of uroliths (bladder stones) are urate stones.
5. Silica stones.
Silica stones account for about 0.1–4% of canine urinary stones worldwide. Silica stones in dogs are mainly caused by silica-rich drinking water or specific brands of pet foods. The type of silica molecule (not the amount of silica) in the food is the crucial factor resulting in silica stones formation. Silica stones are relatively rare in dogs. Male dogs are far more commonly affected by silica stones than females. Silica stones are more commonly found in the lower urinary tract (94%) than the upper urinary tract (1.2%). Silicate stones are tan, hard, rough stores with spicules.
What is the cause of these stones?
These stones are frequently caused by an underlying situation that alters the balance of minerals or other substances that are excreted in the urine. Factors that could influence the risk for the formation of stones include:
Urinary tract infections
Genetic predisposition (the breed of the animal)
Which breeds are prone to kidney or bladder stones?
Certain breeds of animals are more likely to form certain kinds of stones.
Dalmatian *They have a genetic defect in hepatic uric acid metabolism which leads to increased urinary urate excretion.
West Highland white terrier
Calcium oxalate urolithiasis
German shepherd dogs
Old English sheepdogs
Cocker spaniel *The high prevalence of struvite uroliths in the cocker spaniel suggests a familial predisposition in this breed.
Calcium oxalate: adults.
Cystine: 3-5 years.
Urate: 1.5-7 years.
Cystine: males predominance.
Calcium oxalate: male predominance.
Struvite: female predominance.
Urates: male predominance (unless associated with portosystemic shunt).
Is it painful for my dog or cat?
Stones can have sharp edges and can irritate or become embedded in the lining of the bladder, causing the tissue to become thickened and inflamed. They can also form inside the kidneys. Stones can cause serious problems when they lodge in the ureters (the thin tubes connecting each kidney to the bladder) or the urethra (the narrow tube that allows urine to flow from the bladder out of the body). When the normal flow of urine from the kidney to the bladder is obstructed, urine (and pressure) can build up in the kidney, potentially causing kidney infections or kidney failure. If a stone obstructs the urethra, the pet is unable to urinate, and the urine builds up inside the urinary tract. This occurs more commonly in male pets because, compared with females, as they have a long and very narrow urethra. When pets are unable to urinate, it's a medical emergency, and a vet should see the pet immediately.
Can my cat or dog die from this urinary bladder stones?
Urinary obstructions are a veterinary emergency. Without treatment, death occurs in as little as two to three days as toxins build up in your dog's or cat's body. Bladder stones cause frequent urinary tract infections, pain, and blockages, which can be potentially fatal if untreated. So, it's important a vet is contacted immediately bladder stones are suspected.
What is the treatment?
Cats and dogs with blockages may require surgery to remove the bladder stones, and most will also require hospitalization.
Increase in fluid intake is indicated provided there is no obstruction to outflow.
Antibiotics for urinary tract infection.
Dietary modification or provision of prescription diets.
How can this be prevented?
Treat urinary tract infections promptly.
Avoid breeding from predisposed lines.
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Hesse, A., & Neiger, R. ((2009). .). Colour Handbook of Urinary Stones in small animal medicine. Manson Pub.
Houston D.M., M. A. (2010). Stone Disease in Animals. (P. G. Rao N., Ed.) London: Springer. doi:10.1007/978-1-84800-362-0_10
McCue, J., Langston, C., Palma, D., & Gisselman, K. (2009, October 31). Urate urolithiasis. Compendium: Continuing Education for Veterinarians, 31(10), 468-475.
Osborne, C. A., Jacob, F., Lulich, J. P., Hansen, M. J., Lekcharoensul, C., Ulrich, L. K., . . . Swanson, L. L. (1999). Canine silica urolithiasis: Risk factors, detection, treatment and prevention. Veterinary Clinics of North America: Small Animal Practice, 29, 213-230. doi:10.1016/s0195-5616(99)50012-0
Syme, H. M. (2012). Stones in cats and dogs: What can be learnt from them?. Arab journal of urology, 10(3), 230-239.
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