No More Stones: Approach to Cats with Uroliths
World Small Animal Veterinary Association Congress Proceedings, 2019
S. Little
Bytown Cat Hospital, Ottawa, ON, Canada

Causes of Lower Urinary Tract Signs

  • Top common causes in dogs: incontinence, uroliths, bacterial infection.
  • Top causes in cats: idiopathic cystitis, uroliths; bacterial infection is rare.
  • Most common stone types worldwide are struvite and calcium oxalate.



• 77% in females
• Almost all due to bacterial infection
• Upper & lower urinary tract

• 57% in females
• Not infection-induced
• Lower urinary tract only

• 57% in females
• Not infection-induced
• Lower urinary tract only

Calcium oxalate
• 69% in males

Calcium oxalate
• 58% in males
• Lower & upper urinary tract; only stone type in the upper tract


Struvite: Average age <7 years, overweight, inactive, high urine-specific gravity, alkaline urine, Persians

Calcium oxalate: Average age >7 years, overweight, inactive, high urine-specific gravity, acidifying diets, hypercalcemia, certain breeds (Persian, Siamese, Burmese, Devon Rex, etc.)

Proportion of stone types varies by country

Clinical signs: pollakiuria, dysuria, hematuria, inappropriate urination, urethral obstruction (males)

Diagnostic Testing

Most common causes in cats 1–10 years old: idiopathic cystitis, uroliths; important to do survey radiographs.

Most common causes in cats >10 years old: bacterial infection (with concurrent diseases), uroliths, neoplasia; important to do full health workup and urine culture.

Urine should be collected by cystocentesis: 21–23 G needle, 5–10 mL syringe; ultrasound guidance is not needed.

Urine pH and crystal type is not reliable for prediction of urolith type.

Survey radiographs vs. ultrasound


Survey radiographs


Diagnose bladder uroliths

Yes, if radiopaque
>2–3 mm diameter


Assess urolith characteristics (size, number, density, shape)



Assess bladder wall accurately


Yes, if bladder is distended

Identify anatomic abnormalities

Usually no


Radiographic appearance of uroliths



Calcium oxalate


Moderately radiopaque

Very radiopaque


Smooth to slightly rough edges

Smooth (monohydrate) or irregular sharp edges (dihydrate)


Usually <3–5

Usually >3–5

Treatment Options

Three-step approach:

1.  Perform survey radiographs.

2.  If a urolith is present that might be struvite, start therapy with a diet proven to dissolve and prevent struvite uroliths.

3.  Recheck radiographs in 2 weeks; if urolith is at least 50% reduced in size, continue dietary therapy; if urolith is unchanged, check compliance, re-evaluate urolith type.

Methods of bladder urolith removal



1.  ACVIM Small Animal Consensus Recommendations on the Treatment & Prevention of Uroliths in Dogs & Cats.

2.  Appel et al. Evaluation of risk factors associated with suture-nidus cystoliths in dogs and cats: 176 cases (1999–2006). J Am Vet Med Assoc. 2008.

3.  Lulich J et al. (2013). Efficacy of two commercially available, low-magnesium, urine-acidifying dry foods for the dissolution of struvite uroliths in cats. J Am Vet Med Assoc. 243(8), 1147–1153.


Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

S. Little
Bytown Cat Hospital
Ottawa, ON, Canada

MAIN : Case Rounds : Approach to Cats with Uroliths
Powered By VIN