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1014.e2 Urolithiasis, Other

Urolithiasis, Other Client Education
Sheet
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BASIC INFORMATION
• Hematuria
substances, epitaxy [concentric layered
• Pollakiuria crystallization (e.g., deficient inhibitor
Definition • Dysuria formation of a stone of mixed composi-
Urinary tract stones composed of cystine, • Stranguria tion]) also contribute.
calcium phosphate (CaPO 4), or silica are • Inappropriate elimination (periuria) • Silica
uncommon to rare in dogs and cats. • Rarely, systemic illness due to urinary ○ Poorly understood and may be associated
obstruction with ingestion of silica-rich feedstuffs such
Synonyms • Calcium phosphate uroliths may occur as corn gluten feed or soybean hulls
• CaPO 4: apatite uroliths secondary to primary hyperparathyroidism
• Cystine: cysteine (p. 499). DIAGNOSIS
• Cystinuria occurs with Fanconi syndrome
Epidemiology (p. 322). Diagnostic Overview
SPECIES, AGE, SEX Radiolucent uroliths can be missed by routine
• Cystine: uncommon in dogs and rare in PHYSICAL EXAM FINDINGS abdominal radiography but are often identi-
cats. Onset in young adult age; occurs Exam is often unremarkable. Abnormalities fied by ultrasonography or double-contrast
predominantly in males can include cystography. Confirmation of the specific
• CaPO 4 : uncommon in dogs and rare in cats; • Hematuria (stains on prepuce, vulva, or urolith type, which dictates optimal treatment
middle-aged to older animals; prevalence hocks) and prevention, ultimately depends on analysis
varies: brushite. Mostly males; hydroxy- • Painful urinary bladder of uroliths after removal.
apatite, either sex; carbonate apatite, female • Palpable cystic calculi
• Silica: rare in dogs and not described in cats; • Palpable urethral calculi (via digital rectal Differential Diagnosis
onset in middle age; males predominate exam) • Other types of uroliths (struvite, calcium
• Enlarged turgid bladder, if urethral oxalate uroliths most common)
GENETICS, BREED PREDISPOSITION obstruction • Urinary neoplasia
Several breeds are overrepresented for each • Renomegaly, if secondary hydronephrosis • UTI
urolith type:
• Cystine: many, including Newfoundland Etiology and Pathophysiology Initial Database
and Labrador (autosomal recessive trait), • Cystine • CBC: unremarkable
English bulldog, Siamese cats. Prevalence ○ Inborn error of metabolism leads to defec- • Serum biochemical profile: hypercalcemia
greater in Europe than in the United States. tive proximal renal tubular absorption of in some animals with CaPO 4 uroliths. With
Mastiffs and related breeds have an androgen- cystine (± other amino acids) resulting in urinary obstruction, look for azotemia and
dependent cystinuria. cystinuria; not all animals with cystinuria electrolyte abnormalities (p. 1009). In
• CaPO 4 : Yorkshire terrier, miniature schnauzer, form uroliths. patients with cystine uroliths, there may
Bichon frisé, shih tzu, pug, springer spaniel, ○ Cystine is less soluble in acidic urine. be evidence of Fanconi syndrome (p. 322).
Pomeranian, miniature poodle, cocker spaniel ○ Cystinuria occurs as part of Fanconi • Complete urinalysis: hematuria, bacteruria,
• Silica: German shepherd, Labrador, boxer, syndrome. pyuria are found inconsistently.
Old English sheepdog, rottweiler, miniature • CaPO 4 ○ Cystine: aciduria to neutral urine pH;
schnauzer, shih tzu, Lhasa apso, Bichon frisé, ○ Hypercalcemia is contributory but not sometimes flat, hexagonal crystals
Yorkshire terrier essential; there is an association with ○ CaPO 4 : alkaluria (apatite/hydroxyapatite)
primary hyperparathyroidism. to neutral to aciduria (brushite); some-
RISK FACTORS ○ Hypercalciuria may occur without times amorphous or long, thin prism-like
• Cystine: proximal renal tubular transport hypercalcemia. crystals
defect. In certain breeds, cystinuria is ○ Factors decreasing solubility of calcium ○ Silica: pH variable (solubility not linked
associated with being an intact male. salts (e.g., urine pH) or promoting to pH)
• CaPO 4 : primary hyperparathyroidism, distal
renal tubular acidosis, hypercalcemia
• Silica: diets containing corn gluten feed (not
meal) and soybean hulls that are high in
silica
ASSOCIATED DISORDERS
• Urethral obstruction
• Urinary tract infection (UTI)
• Renal dystrophic mineralization
• A link between cystinuria and taurine-
deficient dilated cardiomyopathy has been
proposed in the Newfoundland dog but
remains unproven (cystine is a precursor
for taurine synthesis).
Clinical Presentation
HISTORY, CHIEF COMPLAINT
Clinical signs may be absent. If present, they
may include: UROLITHIASIS, OTHER Microscopic view of urine sediment shows typical hexagon-shaped cystine crystals.
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