Related terms
Crystalluria; Stones, bladder stones
VeNom term
Urolithiasis/crystalluria – calcium oxalate (VeNom code: 2062)
Related conditions
hypercalciuria
Outline
Calcium oxalate stones are formed in the urinary tract when calcium and oxalate ions combine. Himalayan cats have a greater risk of forming stones of calcium oxalate than some other cat breeds. Diet and water intake, and the volume and frequency of urination can influence stone formation. Stones can irritate, inflame and/or damage the bladder or urethral walls, and therefore cause pain, and cats with stones are more prone to urinary tract infections and urinary tract obstruction.
Summary
1. Brief description
Urolithiasis is a condition in which mineral crystals in urine combine to form stones (also called uroliths, calculi or ‘stones’). Stones are classified based on the type of minerals that they are composed of, and commonly are formed from any of 10 different minerals, either combined in various combinations or individually; calcium oxalate stones are formed when calcium and oxalate ions combine. These stones can develop or reside anywhere in the urinary tract – in the kidney, ureter, bladder or urethra – and their presence causes irritation and secondary infection. Most stones end up in the bladder or in the urethra, where they may cause obstruction.
2. Intensity of welfare impact
Small stones may cause minimal adverse effects and can be passed from the urinary tract during urination, without the need for intervention. However, even small stones can irritate, inflame and damage the bladder or urethral walls and thereby cause pain and the appearance of blood in the urine. Urinary tract infections are commonly associated with stones and are likely to cause persistent pain.
3. Duration of welfare impact
Older cats are more commonly affected by calcium oxalate stones, and they commonly reoccur in affected animals. Dietary and environmental management may reduce the risk of calcium oxalate urolith development.
4. Number of animals affected
Calcium oxalate stones are the most common type of urinary stone to occur in cats. Himalayans cats have a higher risk of developing calcium oxalate stones than other breeds.
5. Diagnosis
Stones can be diagnosed with an x-ray or ultrasound scan of the urinary tract. Quantitative analysis of stones is recommended, e.g. via optical crystallography or infrared spectroscopy, to identify which minerals they contain.
6. Genetics
The genetic mechanisms of urolith development in Himalayans are not known, but it is suspected that some factors relating to calcium oxalate urolithiasis may be inherited in this breed.
7. How do you know if an animal is a carrier or likely to become affected?
Currently, it is not known which individual animals are more likely to become affected. We do know that Himalayans cats – especially males – are more at risk of developing obstruction with calcium oxalate stones.
8. Methods and prospects for elimination of the problem
Since the genetic mechanisms for the development of calcium oxalate stones in Himalayans are unknown, the methods for elimination or reduction of the problem are limited.
Clinical and pathological effects
Urolithiasis is a condition in which mineral crystals in urine combine to form stones (also called uroliths or calculi). Stones can be composed of individual or combinations of approximately 10 different minerals, and stones are classified based on the type of minerals that form them. Calcium oxalate is a calcium salt of oxalic acid and forms when calcium and oxalate ions combine; they are one of the most common types of stones in cats; 40% of all feline stones are calcium oxalate (Buffington & Chew 2009). Although there are different combinations of calcium oxalate salts, calcium oxalate stones are most commonly the monohydrate form (crystal name: whewellite) rather than the dihydrate form (weddellite) in cats (Dijcker et al 2011). Stones can develop or reside anywhere in the urinary tract – in the kidney, ureter, bladder or urethra – and commonly cause irritation and secondary infection. Most stones end up in the bladder, kidney or the urethra, where they may cause obstruction (Cannon et al 2007).
Intensity of welfare impact
Small stones may cause minimal adverse effect and may pass uneventfully from the urinary tract, without the need for intervention, during normal urination. However, even small stones can still irritate, inflame and damage the bladder or urethral walls, and therefore affected cats may have difficulties when urinating with pain and discomfort.
Duration of welfare impact
Calcium oxalate stones more commonly affect older cats, with an average (mean) age of 7 to 7.5 years (Lekcharoensuk et al 2000, Picavet et al 2007).
Number of animals affected
The number of calcium oxalate urolithiasis in cats submitted to Hill’s Pet Nutrition Benelux (Belgium, The Netherlands and Luxemburg) increased significantly over a 10-year period from below 50 in 1994 to just below 300 stones in 2004 (Picavet et al 2007).
Diagnosis
Stones can be diagnosed using radiography or ultrasonography of the bladder. Where there are many stones, or when stones are large, veterinarians may be able to physically feel the stones in the bladder.
Genetics
A predisposition to form calcium oxalate stones has been shown to be passed down to family members in humans (Goodman et al 1995) and rats (Bushinsky et al 1995), but to date, has not been reported in cats. Himalayans have a greater risk of developing calcium oxalate stones (Thumchai et al 1996, Lekcharoensuk et al 2000) and these studies suggest that some factors relating to calcium oxalate urolithiasis may be of an inherited nature. However, there may be important environmental factors relating to the way Himalayans are kept, which may cause the predisposition.
How do you know if an animal is a carrier or likely to become affected?
It is currently not known which individual animals are more likely to become affected. We do know that the Himalayan breed is more at risk of developing calcium oxalate stones. Males, especially neutered males are more prone to calcium oxalate stones compared to females and intact males.
Methods and prospects for elimination of the problem
Since the genetic mechanisms for the development of calcium oxalate stones in Himalayans are unknown, the methods for genetic reductions of the problem are limited (Lyons 2010). Further work is necessary to determine the genetic interactions in the pathophysiology of calcium oxalate uroliths in Himalayan cats. Control of diet and environment, for example increased water intake, feeding alkaline or varied diets and access to outdoors, may help reduce the risk of calcium oxalate urolithiasis, even in breeds predisposed to the condition.
Acknowledgements
Science for Animal Welfare thanks Dr Emma Buckland (BSc PhD), Dr David Brodbelt (MA VetMB PhD DVA DipECVAA MRCVS) and Dr Dan O’Neill (MVB BSc MSc PhD MRCVS) for their work in compiling this section.
References
Albasan H, Osborne CA, Lulich JP, Lekcharoensuk C, Koehler LA, Ulrich LK and Swanson LL (2009) Rate and frequency of recurrence of uroliths after an initial ammonium urate, calcium oxalate, or struvite urolith in cats. Journal of the American Veterinary Medical Association 235: 1450–5
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