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Urolithiasis
Synonym(s): Bladder stones, Cystic calculi, Ureteral calculi, Nephroliths
Introduction
- Urolithiasis refers to the presence of stones anywhere in the urinary tract.
- Most canine uroliths are found in the lower urinary tract.
- Most common types: struvite (magnesium ammonium phosphate), calcium oxalate, cystine and ammonium urate.
- Rarer types: calcium phosphate, silica, carbonate, xanthine and drugs or their metabolites.
- Incidence estimated at 0.3-2.8%.
- Cause: (and therefore treatment) depends on type of urolith; usually due to underlying inherited, congenital or acquired metabolic disorder or infection.
- Signs: usually of lower urinary tract disease (may be none).
- Prognosis: many uroliths recur unless underlying cause is corrected, eg infection.
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Presenting signs
- Dysuria.
- Pollakiuria.
- Hematuria.
- In association with urinary tract infection.
- Urinary tract obstruction (upper or lower); usually urethral.
Acute presentation
- Urinary tract obstruction.
- Post-renal acute kidney injury Kidney: acute kidney injury (AKI).
Age predisposition
- Struvite: adult.
- Calcium oxalate: adults.
- Cystine: 3-5 years.
- Urate: 1.5-7 years.
- Struvite: puppies.
Breed/Species predisposition
- Dalmation Dalmatian - urate
. - Miniature Schnauzer Schnauzer: miniature - calcium oxalate, struvite, urate.
- Yorkshire Terrier Yorkshire Terrier - calcium oxalate, urate.
- Dachshund Dachshund - cystine, struvite.
- Bulldogs Bulldog - cystine, urate.
- Newfoundland Newfoundland - cystine.
- Mastiff Mastiff - cystine.
- Lhasa Apso Lhasa Apso - calcium oxalate.
- Bichon Frise Bichon Frise - calcium oxalate, struvite.
- Shih Tzu Shih Tzu - calcium oxalate, struvite, urate.
- Miniature Poodle Poodle: miniature - calcium oxalate.
- Pug Pug – struvite.
Cost considerations
- Emergency therapy for acute urinary obstruction and kidney injury.
- Surgery.
- Tendency to recur.
- Quantitative mineral analysis.
- Radiography.
- Dietary modification.
Special risks
- Acute post-kidney injury due to obstruction Kidney: acute kidney injury (AKI).
Pathogenesis
Etiology
- Supersaturation of urine with crystalloid → crystal nidus (nucleus) formation.
Predisposing factors
General
- Urine pH.
- Diet.
- Metabolic acidosis or alkalosis Acid base imbalance.
- Medication.
- Anatomical abnormalities.
- Lifestyle.
- Gender.
- Sedentary lifestyle.
- Genetic mutation.
Specific
- Urinary tract infection Cystitis (struvite) with urease producing bacteria (eg Staphylococcus and Proteus).
- Portosystemic shunt Congenital portosystemic shunt (CPSS) (urate).
- Hypercalcemia (calcium oxalate).
- Breed.
Pathophysiology
- Inherited, congenital or acquired predisposing condition; depends on nature of urolith.
- Supersaturation of urine with calculogenic crystalloids.
Struvite
- Approximately 50% of uroliths
. - Oversaturation of urine with magnesium ammonium phosphate.
- Urinary tract infection with urease-synthesizing bacteria (eg Staphylococci, Proteus, Enterobacter, Klebsiella, etc) → hydrolysis of urea → ammonia and carbon dioxide → alkaline urine.
- More common in females as higher risk for urinary tract infection.
- Other factors: alkaline urine, high protein diet, genetic predisposition.
Calcium oxalate
- Approximately 30% of uroliths
. - Hypercalciuria.
- Causes of hypercalciuria:
- Intestinal hyperabsorption of calcium.
- Decreased renal absorption.
- Hypercalcemia Hypercalcemia: overview , eg primary hyperparathyroidism, paraneoplastic.
- Hyperoxaluria – primary hyperoxaluria in the Coton de Tulear Coton de Tulear.
Cystine
- Approximately 1% of uroliths
. - Metabolic defect → increased urinary excretion of cystine, lysine, arginine and ornithine.
- Acidic urine → precipitation of cystine.
- Association with entire males in some breeds, resolves with neutering.
Urate
- Approximately 8% of uroliths
. - Dalmatian → defect in hepatic uric acid metabolism → increased urinary urate excretion.
- Defect in hepatic uric acid metabolism can also be seen in other breeds, most commonly in English Bulldogs and Black Russian Terriers Black Russian Terrier.
- Other causes: hepatic dysfunction or portal vessel anomalies (portosystemic shunts) → decreased urate metabolism.
Timecourse
- Uroliths may not be detected until dog is middle-aged.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Lulich J P, Berent A C, Adams L G et al (2016) ACVIM Small Animal Consensus Recommendations on the Treatment and Prevention of Uroliths in Dogs and Cats. J Vet Intern Med 30 (5), 1564-1574 PubMed DOI: 10.1111/jvim.14559.
- Hoppe A & Denneberg T (2001) Cystinuria in the dog - clinical studies during 14 years of medical treatment. J Vet Intern Med 15 (4), 361-367 PubMed.
- Caywood D D & Osborne C A (1986) Surgical removal of canine uroliths. Vet Clin North Am Small Anim Pract 16 (2), 389-407 PubMed.
- Osborne C A & Polzin D J (1986) Non-surgical management of canine obstructive urolithopathy. Vet Clin North Am Small Anim Pract 16 (2), 333-347 PubMed.
- Osborne C A, Klausner J S, Krawiec D R et al (1981) Canine struvite urolithiasis - problems and their dissolution. JAVMA 179 (3), 239-244 PubMed.
Other sources of information
- Osborne C A, Lulich J P, Barges J W (eds) (1999)The Rocket Science of Canine Urolithiasis. The Vet Clin North Am Small Anim Pract 29(1), 1-306.
- Davies M (1996) Management of Canine and Feline Urolithiasis. In: BSAVA Manual of Canine and Feline Nephrology and Urology. Bainbridge J & Elliot J (eds). Chapter 17. pp 209.
- Ling G V & Sorenson J L (1995) Management and prevention of urate uroliths. In: Current Veterinary Therapy XII. Kirk (ed) W B Saunders, Philadelphia. pp 985-998.
- Lulich J P & Osbourne C A (1995) Canine calcium oxalateuroliths. In: Current Veterinary Therapy XII. Kirk (ed) W B Saunders, Philadelphia. pp 992-996.
- Hope A (1994) Canine Lower Urinary Tract Disease. In: Waltham Book of Clinical Nutrition of the dog and cat. Chapter 19. pp 335. (Very useful overview.)
- Osborne C A, Lulich J P, Bartges J W, Thumchai R, Felice L J, Unger L K, Koehler L A, Bird K A & Swanson L (1994) Canine urolithiasis - diagnosis, treatment and prevention. In: Renal Disease in Small Animal Practice. Trenton, NJ: Veterinary Learning Systems. pp 133-150. ISBN 1 884254 18 7 (Useful tables and flow diagrams).