Frequency of Urinary Calculi in Horses

Urinary Calculi, more commonly called urolithiasis, is less common in horses than other rudiment animals. This disease rarely affects young horses. It is seen occasionally in middle age and older horses and is more common in geldings and stallions. The majority of uroliths (stones), occur in the bladder or urethra. They are usually bilateral and produce chronic renal failure before they are diagnosed.

  1. Composition of Stones

    • Most stones are composed of calcium carbonate, with struvite (magnesium-ammonium-phosphate) uroliths seen occasionally.

    Predisposition to stones

    • High mineral content and the pH levels of normal equine urine may predispose equines to crystal formation. Normal equine urine also contains large amounts of mucoproteins, a glycoprotein comprised mostly of mucopolysaccharides, which may serve as a bonding agent for crystals. Forages, which contain large amounts of calcium, ammonia and magnesium, predispose horses to stone formation. Grains with high phosphorus content can also contribute to uroliths.

    Symptoms

    • Symptoms include dysuria (painful or frequent short urinations), colic (acute abdominal pain) and hematuria (passing of blood in the urine). Hematuria is seen most often after exercise.

    Diagnosis

    • Diagnosis is tentatively based on the history and clinical signs, and confirmed by rectal palpation of a firm oval mass at or near the neck of the bladder. Transrectal ultrasonography allows a visual confirmation of the urolith. Urinalysis reveals red blood cells, white blood cells, proteinuria and calcium carbonate crystals.

    Treatment

    • Inserting a catheter into the bladder to decompress it may dislodge an impacted stone. Several surgical procedures are available for urolith removal, including laser lithotripsy--laser destruction of the stone. Prophylactic antibiotics and urinary acidifiers--such as ammonium chloride- after treatment may decrease the formation of new stones.