Nephrolith

From Dog
Macroscopic view of a kidney from a dog which died from chronic renal disease due to nephroliths[1]

Nephroliths are urinary crystals located within the renal pelvis, which distinguishes them from uroliths and ureteroliths.

The causes of nephroliths may be related to lithogenic diets[2], genetic predisposition (e.g. Dalmatians[3], English Bulldog, Russian Black Terrier, Large Munsterlander) but has also been reported in association with renal dysplasia[4] and some drugs such as ceftriaxone[5].

Crystals usually begin to form in the nephron and grow in the collecting ducts after aggregation with other large crystals. Crystal deposits in the collecting ducts near the papillary surface, when exposed to the renal pelvic urine, become nidi for the development of kidney stones[6].

However, it is not uncommon for dogs to have nephrolithiasis, ureterolithiasis and urolithiasis[7]. Bilateral nephroliths also occur but are more rare in dogs.

Nephroliths may obstruct the renal pelvis or ureter, predispose to pyelonephritis, or result in compressive injury of the renal parenchyma leading to progressive chronic renal disease[8].

In dogs, the majority remain static in size and may be undetected for years without clinical symptoms. Some dogs present with acute renal injury characterized by renal pain, fever, anorexia and vomiting. In some dogs, this may be due to perinephric [[abscess] formation[9].

Blood tests may show hyperkalemia and azotemia but this is an inconsistent sign.

Diagnosis is based on presenting clinical signs such as renal pain, blood tests, imaging studies (radiography, ultrasonography and CT scans) as well as excretory urography.

A differential diagnosis would include renal tumors, renal parasites such as Dioctophyme renale and leptospirosis.

Treatment of nephrolithiasis in most canine cases involves a nephrotomy, pyelotomy or salvage ureteronephrectomy. Surgical intervention is indicated in cases where there is evidence for obstruction, recurrent infection, progressive nephrolith enlargement, presence of clinical signs (renal pain), and patients with nephroliths in a solitary functional kidney.

In specialized clinics, alternative treatments would include extracorporeal shock-wave lithotripsy (usually reserved for smaller nephroliths) or percutaneous nephrolithotomy.

Special medical dissolution diets containing amino acid supplements have been reported but are not commonly employed[10].

References

  1. Jeong WI et al (2006) Canine renal failure syndrome in three dogs. J Vet Sci 7(3):299-301
  2. Thompson ME et al (2008) Characterization of melamine-containing and calcium oxalate crystals in three dogs with suspected pet food-induced nephrotoxicosis. Vet Pathol 45(3):417-426
  3. Carvalho M et al (2003) Role of urinary inhibitors of crystallization in uric acid nephrolithiasis: Dalmatian dog model. Urology 62(3):566-570
  4. Yoon HY et al (2010) Bilateral ureteral ectopia with renal dysplasia and urolithiasis in a dog. J Am Anim Hosp Assoc 46(3):209-214
  5. Chutipongtanate S & Thongboonkerd V (2011) Ceftriaxone crystallization and its potential role in kidney stone formation. Biochem Biophys Res Commun 406(3):396-402
  6. Khan SR & Thamilselvan S (2000) Nephrolithiasis: a consequence of renal epithelial cell exposure to oxalate and calcium oxalate crystals. Mol Urol 4(4):305-312
  7. Houston DM et al (2012) 2,8-dihydroxyadenine uroliths in a dog. J Am Vet Med Assoc 241(10):1348-1352
  8. Adams LG (2013) Nephroliths and ureteroliths: a new stone age. N Z Vet J Feb 13
  9. Agut A et al (2004) Left perinephric abscess associated with nephrolithiasis and bladder calculi in a bitch. Vet Rec 154(18):562-565
  10. Mishina M et al (2000) Medical dissolution of struvite nephrolithiasis using amino acid preparation in dogs. J Vet Med Sci 62(8):889-892