Cystic Calculi in a Horse

A teenage gelding presented for the complaint of increased urination (polyuria) and increased water intake (polydypsia). The increased urination had become a significant issue since it was happening at all times including when under saddle and showing. The physical exam was normal and a blood sample was collected for CBC and chemistry analysis. In addition, a free-catch (non-sterile) urine sample was collected during the exam. The CBC and chemistry results were normal suggesting that a primary problem of the kidneys may not have been the cause for the frequent urination. However, the urine sample contained traces of blood, moderate calcium crystals, and moderate white blood cells. These findings suggested an inflammatory process either in the urinary bladder or urethra. A endoscopic exam (cystoscopy) of the urinary bladder was performed. In Figure 1, the internal cavity of the urinary bladder is visualized. A pool of urine is present and a large, yellow object consistent with a urinary bladder stone (cystic calculi) is located in the center of the bladder. The surface of the bladder stone is rough and spiculated. In Figure 2, the inflammation caused by the abrasive stone can be visualized. 

Figure 1

Figure 2

In Figure 3, a pool of "debris" is noted surrounding the bladder stone. This debris is likely made up of calcium crystals, purulent matter (white blood cells), and some bacteria. The irritation caused by the bladder stone likely resulted in hemorrhage within the urinary bladder which is a great media for bacterial colonization! As such, chronic urinary bladder infection or cystitis is a common problem in these patients that will not resolve until the stone and debris is removed. A bladder stone this size can only be removed through a surgical procedure. There are two options regarding surgical approach: 1: bladder exploration via an abdominal incision or 2: through a urethrotomy within the perineum. The latter is performed in a standing horse and is limited to small bladder stones.

Figure 3

The cause of urinary bladder stones in horses is believed to be in part due to diet. Horses consuming diets high in calcium such as alfalfa and drinking water that has a high calcium content may be predisposed to developing urinary bladder stones. However, the condition is relatively rare when one considers how many horses are fed a pure alfalfa diet!  In addition, horses can develop stones in the bladder AND kidneys. These stones may travel and lodge within the ureters and the urethra. In my clinical experience, I have diagnosed urinary bladder stones in 2 geldings and 1 mare. In addition, I have diagnosed kidney and ureter stones in 2 geldings and 2 mares. If the stones obstruct the flow of urine from the kidneys into the urinary bladder they will ultimately result in compromise of kidney function. Common clinical signs include increased urination, increased water intake, recurrent low-grade colic, fever, blood in urine, and poor performance.