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Nephrolithiasis
Synonym(s): Kidney stones, urolithiasis, renolithiasis
Introduction
- Uncommon; sometimes incidental finding, lodged in renal pelvis.
- Nephroliths of different composition possible.
- Signs: can occasionally obstruct urinary flow.
- Treatment: surgery. Treatment may not be necessary.
- Medical dissolution in some cases.
- Lithotripsy possible.
- Prognosis: good if underlying cause removed.
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Presenting signs
- Asymptomatic, incidental finding.
- Chronic renal failure.
- Signs of uroliths in other locations.
- Hematuria.
- Sublumbar pain.
- Pyelonephritis, fever.
- Hepatoencephalopathy in congenital portosystemic shunts and secondary urate calculi.
Acute presentation
- Urinary tract obstruction.
- Obstruction of one kidney may not cause clinical signs, if there is no UTI and the contralateral kidney is normal.
Age predisposition
- Middle age.
Breed/Species predisposition
- Dalmatian Dalmatian (uric acid).
- Dachshund Dachshund (cystine).
- Schnauzer - Miniature Schnauzer: miniature (magnesium ammonium phosphate, calcium oxalate).
- Bulldog Bulldog (uric acid, cystine).
- Yorkshire Terrier Yorkshire Terrier (uric acid).
Pathogenesis
Etiology
Magnesium ammonium phosphate (struvite)
- Alkaline urine.
- Often urinary tract infection, especially with urease-producing bacteria.
- Distal tubular acidosis.
Calcium oxalate
- Acid or neutral urine.
- Hypercalcemia/hypercalciuria (in distal tubular acidosis, Fanconi's syndrome, glucocorticoid excess, excess dietary protein consumption).
- Hyperoxaluria (end product of metabolism of ascorbic acid and amino acids glycine and serine.
Uric acid
- Severe hepatic dysfunction.
- Portosystemic shunt Congenital portosystemic shunt (CPSS).
- Defect in uric acid metabolism and unknown factors (Dalmatian).
Cystine
- Abnormal transport of cystine by the renal tubules.
Predisposing factors
General
- Urinary tract infection (increased risk of struvite, calcium oxalate).
- Breed.
- Urine acidifiers (increased risk of calcium oxalate).
- Magnesium restricted diets (increased risk of calcium oxalate).
Pathophysiology
- A nephrolith comprises both mineral and organic components, the mineral component varying greatly and determined by underlying etiology.
- Supersaturated urine (calculogenic crystalloids) → influenced by pH → decreased renal excretion of crystalloid → calculi forms → grows if able to remain in lumen of excretory pathway of urinary system (urinary stasis).
- Urine = water + excretory products.
- Increased concentration of dissolved substance → increased precipitation of solid material.
- Contributing factors: prolonged supersaturation, concentration of other solutes, pH, absence of inhibitors, presence of a nidus, eg urinary tract infection, prolonged urinary transit time.
Timecourse
- Can form in 2-8 weeks.
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.
Other sources of information
- Ling G V (1995) Nephrolithiasis - Prevalence of mineral type. In: Current Veterinary Therapy XII. Eds: R W Kirk & J D Bonagura. Philadelphia: W B Saunders. pp 980. (Prevalence of different stones, the mixed types and predisposition of different sexes to urinary tract stones.)
- Ling G V (1995) CVT update - management and prevention of urate urolithiasis. In: Current Veterinary Therapy XII.Eds: R W Kirk & J D Bonagura. Philadelphia: W B Saunders. pp 985-989. (In depth study of urate urolithiasis.)
- Lulich J P & Osborne C A (1995) Canine calcium oxalate uroliths. In: Current Veterinary Therapy XII. Eds: R W Kirk & J D Bonagura. Philadelphia: W B Saunders. pp 992-996. (In depth study of calcium oxalate urolithiasis.)
- Osborne C A, Klausner J S & Lulich J P (1995) Canine and feline calcium phosphate urolithiasis. In: Current Veterinary Therapy XII. Eds: R W Kirk & J D Bonagura. Philadelphia: W B Saunders. pp 996-1001.
- Osborne C A, Unger L K & Lulich J P (1995) Canine and feline nephroliths. In: Current Veterinary Therapy XII .Eds: R W Kirk & J D Bonagura. Philadelphia: W B Saunders. pp 981-985. (Prevalence, diagnosis and treatments of most common nephroliths.)