Kidney and Bladder Stones (Uroliths) in Horses

Key takeaways

Urinary stones in horses are masses of minerals which accumulate in the urinary system. They are caused by an abnormal buildup of minerals normally found in the urinary system.

  • The primary cause is suspected to involve an excessive amount of calcium in the diet
  • Symptoms of urinary stones include difficulty urinating, lower abdominal pain or colic, and blood in the urine
  • Diagnostics include physical examination, diagnostic imaging, rectal palpation, blood work, and urinalysis
  • Treatments primarily involve surgical removal of the stone(s) followed by long-term dietary adjustments
  • If recurrence does not happen, prognosis post-surgery is generally good
  • One exception is kidney stones, which have a poor prognosis as they can cause permanent damage to the kidneys leading to renal failure
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A closer look: Kidney and Bladder Stones (Uroliths) in Horses

Some crystallization of minerals in the urine may occur in all mammals and pass undetected. As the crystals become larger, they are more difficult to pass through the small tubes of the urinary system. The larger the crystals relative to the size of the system, the more severe symptoms become.

Risk factors

Urinary stones are rare in horses but more common in males than females. In severe cases, stones can cause a urinary blockage, which is life-threatening. Horses showing symptoms of urinary stones require prompt veterinary assessment. Horses that are unable to pass urine at all require emergency medical attention.

Possible causes

Urinary stones can be caused by excessive calcium and/or other minerals in the diet (for example, alfalfa hay is high in calcium). Urinary stones can be divided into three broad categories which each have specific causes aside from excess dietary mineral and include:

Kidney stones are thought to be associated with kidney damage secondary to anti-inflammatory administration

Bladder stonesare usually associated with urinary tract infections or as a side effect of certain medications causing kidney damage.

Urethral stones are secondary to urine stasis, the incomplete emptying of urine from the bladder.

Main symptoms

Uroliths can be categorized according to where in the urinary tract they form. The symptoms of stones may vary slightly depending on the type.

Testing and diagnosis

Diagnostics begin with physical examination and medical history. Additional diagnostic tests include:

  • Rectal palpation
  • Blood work
  • Urinalysis
  • Diagnostic imaging

Steps to Recovery

Treatment will vary depending on the root cause of the urinary stones but can include:

  • Surgical removal of stones
  • Surgically relieving the narrowing, or creating a permanent hole in the urethra
  • Lithotripsy (laser fragmentation of the stone)
  • Bladder lavage
  • Antibiotics
  • Dietary changes

Prognosis is generally favorable post-surgery if there is no recurrence and dietary changes are followed.

Prognosis in cases of kidney stones is poor as they can cause kidney failure. This risk increases in cases of recurrence.


The main method to prevent urinary stones in horses is dietary management. Reducing calcium and ensuring access to clean, fresh water can reduce the likelihood of stone formation. Minimizing the use of medications (specifically anti-inflammatories) which can cause kidney damage can also prevent stone formation.

Urinary stones are not contagious.

Are Kidney and Bladder Stones (Uroliths) in Horses common?

Urinary stones are not common in horses.

Typical Treatment

  • Surgical removal
  • Perineal urethrostomy
  • Lithotripsy
  • Bladder lavage
  • Antibiotics
  • Dietary changes

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