A circulatory coincidence: When a gelding develops an unusual blockage in a neck vein, his owner is in a unique position to identify the problem.
Like many horses, Simon found his people in a roundabout manner. The journey started when Nuala C. Galbari and her partner David L. Justis, MD, PhD, started half-leasing the palomino Tennessee Walking Horse with another rider in 2014.
The couple was smitten with the gelding, who was perfect for their lowkey riding style. “He has some issues with nerve damage in his back, so we had to experiment with saddles to find one he was comfortable with, but he does light work in the arena, including cavalletti,” says Galbari. Although he can be standoffish in his stall, Simon was a willing mount. “He’s a great little horse---as calm as can be. I don’t think he has ever spooked,” she says.
The other lessor, however, didn’t develop the same relationship with Simon. “The two of them just didn’t get along,” says Galbari. After a few short months, the other woman stopped leasing the gelding, leaving the couple with a decision. “We thought about sending him back to our trainer, but by that point we were pretty attached to him, so we ended up purchasing him instead.”
Whether it was luck or fate that brought Simon and his owners together, the partnership would take on new significance three years later when the gelding developed a condition that is rare in horses, but was all too familiar to his new owners.
An unusual swelling
It was a sweltering July afternoon in Virginia when Galbari and Justis arrived at the boarding barn to visit Simon and their other horse, a Thoroughbred named Captain Jack.
“I was the one who noticed the swelling on Simon’s neck,” says Justis, “and I saw it immediately.” About the width of a pencil, the swelling began just below the gelding’s left ear and extended downward along the side of his neck toward his withers. Around the midpoint of his neck, there was a slightly larger swelling, which was firm to the touch. Simon did not seem to be in distress; he was eating and drinking, and his temperature and respiratory rate were normal.
It took Justis only seconds to recognize what he was seeing---in fact, he was uniquely qualified to assess the condition. “I knew instantly that it was a blood clot in an external vein with associated swelling called thrombophlebitis. My doctorate is in biochemistry with a specialization in clotting disorders. I’m pretty familiar with the condition,” he says. Indeed, Justis was one of the leading researchers in his field, working with the famed Mayo clinic in Minnesota for nearly 30 years until his retirement.
Thrombophlebitis has two components, explains Justis: inflammation of the vein wall and clot formation within the vein lumen (interior). The inflammation is usually triggered by some type of trauma to the vein, which also triggers the release of clotting factors, leading platelets to stick together to form the clot. “It doesn’t take much to start that cascade of events,” he says. “I’ve seen clots develop from simple sunburns in humans.”
In horses, however, thrombophlebitis and clots are rare. “It wasn’t something I’d heard or read about in horses,” says Justis, who snapped a series of pictures to send to veterinarian Steven King, DVM, at Pine Meadow Equine in nearby Yorktown.
King looked at the pictures and agreed with Justis that Simon likely had thrombophlebitis and an associated clot. What made this case especially unusual, says the veterinarian, was its spontaneous nature: “Usually you hear about these happening in a hospitalized horse with an indwelling catheter in the jugular vein,” he says. “The inflammation is associated with the puncture of the needle or irritation from the catheter. They can be extensive or fairly minor, but they are almost exclusively seen in a clinical setting.”
Both men had theories on why Simon may have developed the swelling. “My thinking, given the time of year, is that an insect bite had triggered the inflammation,” says Justis. “If the bite punctured the vein directly, I think
When a gelding develops an unusual blockage in a neck vein, his owner is in a unique position to identify the problem. By Christine Barakat
that could be enough.” King agreed that an insect bite could be the cause but also raised the possibility that some other traumatic trigger, such as a kick from another horse or a blow against a fence, had irritated the vein enough to lead to the swelling.
There was also the possibility that Simon had some other underlying illness that caused the clot to form first, occluding his vein and triggering the inflammation. “When we see a hypercoagulable state in people we think of a genetic defect or another factor,” says Justis. “For instance, people who have lupus are more prone to clotting.” Simon, however, had always seemed perfectly healthy with no signs of any genetic or chronic condition.
“It was possible that there was some very strange underlying clot-causing illness causing the clot but, given there didn’t appear to be anything else wrong with him, that was highly unlikely,” says King. “It was much more likely that it was caused by a minor trauma.”
Wait and see
Exactly what was causing the problem wasn’t the most important question, though. The more pressing issue was the sort of treatment Simon might need. Again, Justis and King used their combined experience to devise a plan.
“Of course, in humans, you worry about a clot breaking free and traveling to the brain or the lungs,” says King. “But this was in a vein, which was traveling back to the heart, in a fairly large animal. There would be a long way for a clot to travel before it reached a critical area and it would very likely break up on its own before it got there.”
“In humans with a history of clots we might give the drug heparin,” says Justis. “It inhibits clotting and can help break up existing clots, but that might not be a good idea in a horse who is going to be turned out in a field with other horses. He could roughhouse or get banged around, and if he’s unable to clot, that would be a dangerous situation.”
King agreed with that assessment. “We discussed giving a medication to break up clots, but not knowing too much about the potential effects in a horse and given that Simon wasn’t in any pain or discomfort, we didn’t think it was necessary. When a vein is occluded or cut, the blood can often find other ways around in the system, so there wasn’t an immediate risk of any tissues starving either.”
In cases of thrombophlebitis associated with an indwelling catheter, treatment typically consists of antiinflammatory medication if the horse is in pain as well as antibiotics to treat the infection that may have triggered the swelling in the first place. In the most serious and persistent cases, a surgeon may attempt to remove the clot or reopen the vein. Fortunately, Simon’s swelling showed no sign of
needing any such intervention.
The plan, then, was to give the gelding’s body time to break up the clot on its own. “In humans we would use moist heat to help improve circulation and get venous drainage,” says Justis. “But it was July in Virginia, so it was already plenty warm and moist outside. In humans we would also keep the area elevated, but you can’t really tell a horse to do that. I suppose if it had gotten to that point, we could have used a neck cradle to keep his head up, but that never became necessary.”
Justis did massage the vein slightly to encourage circulation and noted that Simon didn’t object to that. “Massaging the vein didn’t make the swelling go down right away, but I wouldn’t have expected it to,” he says. “In humans it can take a week to 10 days for the body to break down the clot on its own. Until that happens, you’ll still see some swelling.”
The next day, King traveled to the farm to get a firsthand look at Simon’s neck. “I’d seen the pictures from the previous day and it was already starting to resolve a bit,” he says. “He wasn’t showing any signs of distress or illness, so we stuck with our plan of just waiting for his body to handle it.”
Over the next few days, the swelling diminished at a steady pace under Justis’ watchful eye. A week after it was discovered, Simon’s thrombophlebitis was nearly gone and the lump under the skin where the clot had been was barely detectable.
“To be cautious, I didn’t ride him during that time---we only hand-walked him,” says Justis. “I’m not sure it was necessary, though. He was eating well and his manure was normal. It was a very uneventful recovery.”
So far, so good
Justis and Galbari continue to keep a close eye out for any new swellings, but so far they’ve found none. “I do wonder if these happen on horses more often than we think and just go undiagnosed or undetected,” says Justis, who recognizes the irony and good fortune in his horse developing the very problem that he spent his career researching.
“I was in a unique position to
recognize it and go looking for more information,” he says. “Honestly, there’s not a lot a lot of literature on equine clotting problems. I know dogs and turkeys throw clots, but I haven’t been able to find much in terms of the risk in horses. It might be that their large size protects them. There have been studies of giraffes on this topic---how do they avoid clots in their large necks, so far from their hearts, grazing with their heads down? It turns out they have a series of valves in their jugular system. I’d be interested in learning if horses have a similar system, but if horses aren’t regularly developing clots, it’s understandably not a research priority.”
King suspects thrombophlebitis occurs in horses more often than we realize. “I’m sure this happens as part of the inflammatory process,” he says. “Tissues swell and occlude veins deeper in the musculature. What was so odd in this case is that it happened on an external vein under a thin summer coat, so it was more noticeable.”
Even if the condition in horses is
more common than we might realize, an owner who discovers such a swelling is wise to call their veterinarian right away, says King. “Even though it’s not likely to be a serious problem, it’s one of those things you’ll want to investigate to be certain of what you’re dealing with,” he says. “For instance, it could be related to a puncture wound that could eventually abscess. This case turned out well, but we were keeping close tabs on him, and that’s important. If at any point he’d developed other signs of trouble, we’d have gotten more involved.”
The plan was to give the gelding’s body time to break up the clot on its own.
RESOLVED: The day Simon’s thrombophlebitis was discovered ( top), the swelling was thick and distinct. Three days later ( left), the inflammation had subsided significantly. A week after the swelling was first noticed, it could barely be detected (...