related term: cystinuria
What is urolithiasis?
Urolithiasis is a condition in which crystals in the urine combine to form stones, also called calculi or uroliths. These can be found anywhere in the urinary tract, where they cause irritation and secondary infection. Most end up in the bladder or urethra.
Several different types have been identified, with struvite stones (magnesium ammonium phosphate) being by far the most common, except in the Dalmatian. Any breed can develop uroliths, but a genetic predispostion to producing crystals makes the development of stones more likely.
Dalmatians have a defect in the pathway that normally leads to the breakdown of urates, which are a by-product of protein digestion. This results in increased urate excretion in the urine (4 to 8 times that of other breeds), and this predisposes them to the formation of urate crystals and eventually, stones.
In some other breeds, an inherited defect in a different pathway causes excessive urinary excretion of the amino acid cystine, resulting in cystine crystals and potentially stones in the urine.
type of crystal/stone breeds affected inheritance treatment prevention
struvite -(triple phosphate, MAP) cocker spaniel, miniature schnauzer, bichon frise, seen in many other breeds as well. This is the most common type of stone seen, but little is known about inheritance. Dissolve medically or remove surgically. Feed special diet; acidify urine
urate-Dalmatian, English bulldog. Autosomal recessive. Dissolve medically or remove surgically. Provide special diet (reduced purine) and, if necessary, use allopurinol; alkalinize urine
calcium oxalate -Lhasa apso, miniature poodle, miniature schnauzer, Yorkshire terrier little is known remove surgically feed special diet; supplement with potassium citrate
cystine- English bulldog, dachshund, Newfoundland, Irish and Scottish terrier. Autosomal recessive in Newfoundland and suspected in Irish and Scottish terrier. Alkalinize the urine by increasing vegetable protein in the diet, +/- supplement with sodium bicarbonate.
xanthine -Cavalier King Charles spaniel thought to be autosomal recessive
For many breeds and many disorders, the studies to determine the mode of inheritance or the frequency in the breed have not been carried out, or are inconclusive. We have listed breeds for which there is a consensus among those investigating in this field and among veterinary practitioners, that the condition is significant in this breed.
How is urolithiasis inherited?
The trait for high urate excretion is autosomal recessive in the Dalmatian. The gene pair responsible is genetically linked to the gene pair responsible for the absence of white hairs in the spots, so that selection for sharply delineated black spots may have accidentally also resulted in selection for high urate excretion.
The trait that results in high cystine in the urine (called cystinuria) appears to be autosomal recessive in the Newfoundland, and in the Irish and Scottish terrier.
What does urolithiasis mean to your dog & you?
The changes in the urine are generally present from birth. However it usually takes some time for crystals to form and combine into stones that cause problems, most often between 3 and 6 years of age. The signs you will see in your dog depend on where in the urinary tract the stones end up. They collect most commonly in the bladder, in which case you may see blood in the urine, difficulty and pain in urinating, and small frequent amounts of urine. If a stone completely obstructs the urethra and thus blocks the outflow of urine (more common in male dogs, who have smaller urethras), then these signs of discomfort will be magnified and your dog may also show signs of kidney failure - vomiting,depression, loss of appetite.
How is urolithiasis diagnosed?
If your dog is showing the physical signs described above, your veterinarian will do an analysis of his/her urine (urinalysis) to look for crystals and also for a bacterial infection, which is commonly seen with this condition. Many stones can be seen with x-rays; some (especially urate uroliths) will only show up with contrast radiography. Ultrasound can generally detect stones of all types.
A DNA test is available to detect cystinuria in Newfoundlands, making it possible to identify affected, carrier, and clear animals.
For the veterinarian: Types of uroliths vary in radiodensity. Calcium oxalate uroliths are usually obvious on radiography; urate uroliths may be radiolucent and therefore require contrast radiography or ultrasonography.
How is urolithiasis treated?
A combination approach is usually needed. Stones are often small and numerous. Larger ones may be removed surgically - this is preferred if your dog is in pain or the stone is blocking the ureter or a kidney. Stones may also be fragmented by laser shockwaves, so they are small enough to be passed in the urine. The medical approach is to dissolve the stones gradually by changing the pH of the urine, ie. making it more or less acidic (depending on the type of stone) through medication and changes in diet. Special diets also result in a larger volume of more dilute urine, making it easier for a dog to pass the stones. Your veterinarian will monitor your dog's progress through periodic radiographs and analysis of the urine over the period of time the stones are dissolving (which can take some months). Some types of stones are more amenable to dissolution than others.
In all cases of urolithiasis, in addition to paying careful attention to your dog's diet, you can help to reduce the formation of stones by providing lots of fresh water and regular opportunities to urinate, so that urine doesn't accumulate in the bladder allowing time for stones to form. You can increase your dog's water consumption by feeding a canned diet with a high water content, or mixing dry food with water.
Bacterial urinary tract infections are common with urolithiasis, and should be treated promptly.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.
Ackerman, L. 1999. The Genetic Connection: A Guide to Health Problems in Purebred Dogs.182-186. AAHA Press, Lakewood, Colorado.
Osborne,CA and Finco, DR. 1995. Inherited and congenital disease of the lower urinary tract. In Canine and Feline Nephrology and Urology. p. 681-692. Williams and Wilkins, Philadelphia.
Lulich, JP, Osborne, CA, Bartges, JW, Polzin, DJ. 1995. Canine lower urinary tract disorders. In E.J. Ettinger and E.C. Feldman (eds.) Textbook of Veterinary Internal Medicine, p. 1833-1861. W.B. Saunders Co., Toronto. - contains good protocols for management and prevention of the different types of uroliths, including stubbornly recurring ones.
Copyright © 1998 Canine Inherited Disorders Database. All rights reserved.
Revised: November 24, 2003.
This database is a joint initiative of the Sir James Dunn Animal Welfare Centre at the Atlantic Veterinary College, University of Prince Edward Island, and the Canadian Veterinary Medical Association.