FieldDxUrolithiasis in HorsesClinical signs, differential diagnosis, treatment and prevention in horses.
Overview
Formation of mineral stones in the urinary tract of horses, less common than in ruminants. Precipitation of calcium carbonate crystals (the predominant equine urolith type) from urine, the exact triggering factor often not identifiable in an individual case.
Clinical signs
- Dribbling of urine reflecting inadequate or lack of sphincter control, associated with incomplete obstructive urolithiasis.
Predisposing factors
- Mainly older animals, and males, with geldings overrepresented; no breed predilection appears to exist.
- Normally alkaline urine rich in minerals favours calcium carbonate stones, and high urinary mucoprotein can bind minerals and help stones form.
- NSAID-associated renal papillary necrosis may predispose to kidney and ureter stones.
- High-calcium feeds such as alfalfa and other legumes.
Treatment
- Surgery is the usual treatment — perineal urethrotomy or manual urethral dilation in males, followed by removal of intact or lithotripsy-fragmented stones.
- Ultrasonographic examination of the kidneys and ureters, plus urine culture and urolith analysis, are performed after removal to guide prevention and check for additional stones.
Prevention
1. Balance mineral intake from all feed and water against nutritional needs and stone composition. 2. Restrict high-calcium feeds such as alfalfa and other legumes. 3. Urinary acidification is hard in hay-fed horses; ammonium sulphate may work briefly in some, and long-term acidifying salts should be used cautiously in athletic horses because of osteoporosis risk. 4.
Source
MSD Veterinary Manual — Urolithiasis in Horses (accessed 2026-08-11)
MSD Veterinary Manual — Urolithiasis in Horses (accessed 2026-10-29)
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Passage 151). A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Passage 153). A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Passage 151).
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