Here in Central Oregon, we are unlucky enough to have a relatively high incidence of bladder and kidney stones (called “uroliths,” “cystoliths,” or “nephroliths,” depending where in the urinary tract they occur) in our equine population. While we don’t know for sure why this is the case, we suspect it has to do with the mineral content of our groundwater.
Clients often initially seek veterinary care for this problem because they notice their horses seem uncomfortable while urinating (sometimes groaning) or are urinating in small amounts frequently. Symptoms may worsen during exercise. Sometimes the horse or donkey’s urine will show a tinge of blood as well, though this can be a variable finding. In the worst-case scenario, the stones may travel down the urethra and completely obstruct it, which is a life-threatening condition. In these cases, the horse may show severe colic signs.
A urinalysis of an affected horse may show increased protein levels, and sometimes blood, but cannot rule in or out bladder or kidney stones.
The next diagnostic is often a transrectal bladder palpation. During palpation, we may identify bladder stones by their feel in the bladder; this can sometimes be challenging if the bladder is full or the stones are small. Transrectal ultrasound may be used give us more information about the bladder. We an also use ultrasound externally to examine the kidneys and identify kidney stones.
An endoscopic bladder exam is the best modality for bladder stone diagnosis. This allows us to visualize the stones, determine their number and size, and even remove them with a snare through the endoscope via the urethra if they are small enough.
Stones larger than 1 cm in diameter typically require surgical removal. There are both standing and general anesthesia surgical options, depending on the size and number of the stones and the horse’s temperament and gender. Bladder stones can be easier to remove in mares because of mares’ short urethras, but if the stones get large, they become more difficult and invasive to extract.
If your horse shows any signs of urinary discomfort, reach out to your veterinarian sooner rather than later so that we can hopefully identify stones while they’re small and have a more streamlined treatment option!