An Equine Bladder-Stone Blockage

When an affable gelding suddenly develops trouble urinating, only emergency surgery can save his life.

Tucker is one of those rare horses who can please anyone. “If you’re a beginner, he’ll take care of you,” says his owner Jim Mackler. “If you know how to ride, he’ll step it up and give you a good one.”

Mackler and his wife Judy bought the sorrel Quarter Horse gelding in 2002, when he was 7 years old. Five years later, in late winter, they began to notice he was having problems urinating. “He began straining and grunting every time,” says Mackler. “And he’s not a complainer.”

Tucker was urinating frequently in short streams that over the course of about three weeks eventually petered out into slight

trickles and then dribbles. Worried, the Macklers called their regular veterinarian, Dennis Farrell, DVM, of Ridge, New York, to come and check Tucker out.

Some bladder stones can be broken up into small pieces that are passed out with the urine. Because Tucker’s stone was so large and solid, however, it had to be removed surgically. ©Tom Moates

Tucker’s signs were consistent with a urinary infection, a painful inflammation in the urethra and/or bladder caused when bacteria or fungi from the surface of the skin invade the urinary tract. Horses with this condition often strain to urinate, with frequent attempts that produce only small amounts of fluid or none at all. “[When investigating a problem] you start with what happens 95 percent of the time,” says Farrell. “So we looked for infection, took a blood sample, cleaned his sheath and put him on some antibiotics.”

Within days, the dribbling cleared up and Tucker seemed more comfortable, but over the course of a week or so all the signs of trouble returned. Farrell prescribed another course of antibiotics and again the signs cleared up, only to return. This cycle went on for nearly six weeks into early March.

The Macklers and Farrell explored other possible causes for Tucker’s issue, but they kept coming up short: The other horses living with Tucker were on the same feed and running in the same paddocks, and none showed problems of any kind, so some type of environmental toxin was unlikely. Urinary infections in horses often occur in conjunction with other illnesses or skin infections, but Tucker had never spiked a fever and he was otherwise healthy. Other than the strange urination, there didn’t seem to be anything wrong with the gelding.

All blocked up
The break in the case came when Tucker began showing mild signs of colic one afternoon. As Farrell did a rectal exam to check for impactions, he noticed that Tucker’s bladder was very full and extended. Normally, a horse would be anxious to empty it, but Tucker showed no signs of trying. Farrell passed a catheter up the gelding’s urethra and into the bladder to evacuate the urine. Once his bladder was empty, the signs of Tucker’s colic vanished. “He went from miserable to chipper in a matter of minutes,” says Jim Mackler.

This was an important clue, which told Farrell that the gelding had an issue with his bladder—something was preventing him from emptying it. Farrell performed another rectal exam to feel the empty bladder. “That’s when I felt a mass,” he says. Through the muscular walls of the organ, he could feel a round, hard object. It was, in all likelihood, a bladder stone.

Bladder stones are rare in horses.”I’ve seen this twice in 25 years,” Farrell says. The causes of this are not known, but most develop in a predictable way: Under certain conditions, dead cells, proteins and minerals that are normally washed out with a horse’s urine collect to form tiny crystals. Additional cells and debris then become attached to one or more of these crystals, called niduses, to form larger rocklike masses. If these get big enough, they remain trapped in the bladder, where they can block the entry to the urethra and prevent the outflow of urine. Most of these stones are composed primarily of calcium carbonate, but other minerals, such as magnesium and phosphorus, may be included as well.

Male horses are much more likely to develop bladder stones than mares are because of differences in their anatomy. The female horse’s urethra is shorter, wider and distends more easily than a male’s, and so small and moderately sized particles can pass out more readily, and larger masses are less likely to develop.

All of Tucker’s signs were consistent with bladder stones: first the dribbling and straining, and then the colic once the stone had grown large enough to prevent him from urinating at all.

Make way
Tucker’s situation was an emergency. If his bladder filled again while he remained unable to urinate on his own, the organ could rupture. Farrell immediately referred the gelding to the Mid-Atlantic Equine Medical Center in Ringoes, New Jersey, and the Macklers loaded him up for the 100-mile trip.

Patty Doyle-Jones, DVM, DACVS, met Tucker when he arrived. “I knew he had been exhibiting a history of painful urination and dribbling, and that Dr. Farrell had felt what he thought was a stone,” she says, “but [otherwise] Tucker was a healthy horse when he got here.”

Doyle-Jones started by performing a rectal exam to feel the mass herself before continuing on to more thorough diagnostic techniques. “We did ultrasound imaging of his kidneys,” she says. “The left one was normal, and he had some slight calcium grit in his renal pelvis on the right side—not like very large stones or anything, but there was some grit there. And then we ran the endoscope up from the penis into the bladder, and you could see the bladder stone sitting right there. We estimated the stone to be eight centimeters across.”

Several techniques exist for removing bladder stones. They can be surgically removed, or sometimes they can be shattered within the bladder into pieces small enough to flush out with the urine. This second approach, called lithotripsy, can be accomplished with lasers, with shock waves or manually, with a long metal tool called a lithotrite that is inserted in the urethra. Lithotripsy is less invasive than surgery, but it does carry the risk of burning, abrasion or other injury to the bladder wall, and sometimes the initial procedure may not break the stone into small enough pieces. Which approach is best for each case depends on several factors, including the gender of the horse and the size of the stone.

Gender matters, again, because of the differences in the size and shape of the male and female urethra. “The position of the urethra on the floor of a mare’s bladder makes it easier for small particles to be voided with urine,” says Doyle-Jones. “If they do develop stones, they are easy to reach and break up so they can be passed. Some smaller handed vets can actually reach through the urethra into the bladder and remove them directly.”

But a gelding’s longer urethra not only makes the stone harder to reach, the position of its opening in the bladder also makes it difficult to flush the debris if it is crushed. A veterinarian might have to repeatedly flush the bladder, then use an endoscope to ensure all of the pieces had been cleared.

Nevertheless, Doyle-Jones says that the majority of bladder stones she sees do not require major surgery: “Most of them you can treat standing because they are small enough when they’re diagnosed you can just go in and pull them out. The larger ones are not all that common.”

But Tucker’s stone was very large and solid. “We decided the better option was to put him under general anesthesia and remove the entire stone at once,” says Doyle-Jones. (She adds that lithotrite designs have improved since 2007, when Tucker was treated, and they are now more effective than they were then. If she faced the same case today, Doyle-Jones says, she might try to break the stone manually.)

Relief at last
Tucker was positioned on his back for the procedure, and Doyle-Jones made an incision near his sheath to access his abdominal cavity. For a horse in this position, the bladder has to be lifted up from the floor of the pelvis to the opening in the abdomen. “You have to work it carefully to allow the smooth muscle to relax in order to lift it and position it for the incision,” says Doyle-Jones.

Once the bladder was in place, surgical drapes were placed around it to prevent any urine from leaking back into Tucker’s body. Doyle-Jones made a small incision in the organ, reached in and removed the stone. Then she sutured the bladder closed, repositioned it back in the body and closed the primary incision.

Tucker recovered at the clinic for the next week. He received antibiotics, anti-inflammatory drugs and painkillers. He was also monitored to make sure he was urinating normally. “Usually horses have no problem with bladder function after this,” says Doyle-Jones. “We didn’t put a catheter in Tucker and we typically don’t have to. The bigger concern is infection at the primary incision, and he didn’t show any signs of that.”

Tucker’s convalescence continued after he returned home. “He was on stall rest for about a month to make sure he didn’t damage his incision,” says Judy Mackler. “But when he went back out with his friends he had no problems at all. We started riding him shortly after that.”

The Macklers also continued to monitor his urination habits. Horses who have had bladder stones are at a slightly higher risk of recurrence in the immediate period after removal, especially if the stone was broken and some particles were left behind. But, says Doyle-Jones, after they have been free of stones for several months, they are no more at risk than any other horse.

Since his procedure, the Macklers have never seen Tucker groan, strain or dribble while urinating, but Judy comments that he does seem to go more often then he did before.

“It’s possible they are just more aware of when he goes,” says Doyle-Jones. “Or it’s possible there is a very small adhesion or scar that’s limiting how far his bladder can expand. As long as he appears to be voiding normally when he does go, there’s no need to worry.”

The only permanent change the Macklers have made in Tucker’s care is to remove alfalfa hay from his ration. Although it’s not known why horses develop bladder stones, one theory is that high levels of calcium in a horse’s diet may contribute to the problem, and alfalfa contains significantly more of that mineral than grass hays. This possibility cannot be the entire answer, because many horses regularly eat alfalfa and never develop the stones. But just as a precautionary measure, Doyle-Jones suggested switching Tucker off of alfalfa altogether, a policy that the Macklers have strictly adhered to ever since.

In theory, changing the diet to increase the acidity of a horse’s urine could also prevent the recurrence of bladder stones, since calcium carbonate needs an alkaline environment to form crystals. But, says Doyle-Jones, “We’ve never really found a way to keep the urine acidified enough to keep that calcium carbonate from forming those stones. We never do really figure out why they have it.”

In the five years since Tucker’s bladder stone episode, he has continued to be healthy and active with no further signs of trouble. And he is still a charming all-around horse anyone can ride. “He’s really one in a million,” says Jim Mackler.





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