Canis ISSN: 2398-2942

Nephrolithiasis

Synonym(s): Kidney stones, urolithiasis, renolithiasis

Contributor(s): Kathy Lunn, Phil Nicholls

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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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 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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Outcomes

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Further Reading

Publications

Refereed papers

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.)


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