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 (...

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