An el­e­gant re­pair

The so­lu­tion to a mare’s re­cur­ring post-sur­gi­cal her­nia is a new tech­nique that uses an an­cient fiber.

EQUUS - - Eq Casereport - By Chris­tine Barakat

Lily’s colic surgery went smoothly. The 8-year-old mare had been rushed to Tufts Univer­sity in Mas­sachusetts with acute gut pain, and ex­ploratory surgery re­vealed a left dor­sal dis­place­ment of her large colon. The sur­geons cor­rected the dis­place­ment, su­tured the in­ci­sion in the mare’s ab­domen and sent her home a few days later.

That’s when the com­pli­ca­tions be­gan. “When you’re open­ing and clos­ing an ab­domen, there’s a lot that can go wrong,” says Jose Gar­cia-Lopez, VMD, DACVS. “There are mul­ti­ple lay­ers of mus­cle to su­ture, along an in­ci­sion line that can be 40 cen­time­ters long. Then, af­ter you’re done, the horse stands up, and grav­ity puts hun­dreds of pounds of vis­cera right on the in­ci­sion you’ve just su­tured. To put it in con­text, imag­ine if af­ter you had ma­jor ab­dom­i­nal surgery, your doc­tor told you to get on all fours and crawl around. That’s ex­actly what we ask horses to do.”

That’s why her­nias---the protru­sion of an or­gan or body tis­sue through an open­ing in the ab­dom­i­nal wall---are a rel­a­tively com­mon com­pli­ca­tion of colic surgery. Sur­geons have de­vel­oped a va­ri­ety of tech­niques to su­ture in­ci­sions as se­curely as pos­si­ble, but her­nias still de­velop in 10 to 20 per­cent of horses. “Sur­gi­cal her­nias oc­cur when the linea alba, the fi­brous band of tis­sue that runs along the mid­line, fails at the site of the in­ci­sion,” says Gar­cia-Lopez. “In­fec­tion in­creases the risk of this hap­pen­ing, but it can hap­pen in a healthy wound, too. Es­sen­tially, the ab­dom­i­nal wall pulls apart at a weak spot, cre­at­ing a pouch of sorts.”

That pouch can then fill with fluid and ex­pand, cre­at­ing space for ab­dom­i­nal struc­tures to slip in. “What you see from the out­side is a bulge along the mid­line,” says Gar­cia-Lopez. “If you touch it, it will usu­ally feel soft.”

Some her­nias are in­con­se­quen­tial ---they may look un­pleas­ant, but they do no harm to the horse. “Many times the bulge is cre­ated by a small piece of fat or omen­tum that slips down into the pouch,” says Gar­cia-Lopez. “That isn’t too wor­ri­some.” A horse with a be­nign her­nia may even be rid­den, although a pen­du­lous bulge may in­ter­fere with more ath­letic ef­forts.

Other her­nias, how­ever, can be quite dan­ger­ous. “If a por­tion of bowel or in­tes­tine slips down into the space, par­tic­u­larly through a small open­ing, it can be­come stran­gu­lated, with the blood cut off, and be­gin to die,” says Gar­ci­aLopez. “Then you’ve got a po­ten­tially deadly colic emer­gency on your hands.”

Her­nias can usu­ally be cor­rected sur­gi­cally, although it may not be nec­es­sary if the ab­nor­mal­ity poses no harm to the horse. Typ­i­cally, a vet­eri­nar­ian will ex­am­ine the bulge with ul­tra­sound to de­ter­mine its con­tents to as­sess any po­ten­tial dan­gers. “Most own­ers, in my ex­pe­ri­ence, opt to re­pair her­nias,” says Gar­cia-Lopez. “It does in­volve another surgery, but in many ways that is bet­ter than wor­ry­ing about what might hap­pen down the road.”

A failed fix

A fist-size bulge ap­peared along Lily’s mid­line within weeks of her colic surgery, prompt­ing her own­ers to call in their reg­u­lar vet­eri­nar­ian. “Her own­ers still rode her regularly and were plan­ning on us­ing her as a brood­mare,” says Gar­cia-Lopez. “They weren’t wor­ried about aes­thet­ics, but they were con­cerned about what might hap­pen with the her­nia through preg­nan­cies.”

Af­ter con­fer­ring with their vet­eri­nar­ian, Lily’s own­ers agreed to a her­nia re­pair pro­ce­dure done on the farm. The mare was anes­thetized and laid down in a clean grassy area. The vet­eri­nar­ian then re­opened the failed in­ci­sion line, repo­si­tioned the bulging tis­sues and su­tured the ab­domen closed once again. Lily woke from the anes­thetic and stood up with­out any com­pli­ca­tions.

To help pre­vent a re­cur­rence, the vet­eri­nar­ian out­fit­ted Lily with a her­nia belt. “These are stretchy belly wraps that se­cure with strong Vel­cro,” says Gar­cia-Lopez. “They are cut to par­tic­u­lar sizes to fit cer­tain mea­sure­ments

and fit very tightly. These wraps are es­sen­tially corsets that you leave on a horse for sev­eral weeks af­ter the surgery. Stud­ies have shown that us­ing them im­me­di­ately post-surgery can re­duce the stress on the in­ci­sion line as well as the amount of edema or swelling present, which, po­ten­tially, re­duces the risk of a her­nia.”

For a time, the re­pair seemed to have worked. But when the her­nia belt was re­moved, the de­fect in the in­ci­sion line slowly reap­peared. Within months, another bulge emerged in the ex­act same lo­ca­tion. Frus­trated, but de­ter­mined to help their mare, Lily’s own­ers loaded her up and headed back to Tufts.

Once she ar­rived, Gar­cia-Lopez con­ducted a com­plete ex­am­i­na­tion of the mare. But be­yond the bulge in her mid­line---about three inches long and one-and-a-half inches wide---Lily was in good health and spir­its. Although the ul­tra­sound did re­veal large bowel within the her­nia, there was no ev­i­dence of im­me­di­ate dan­ger of an in­testi­nal stran­gu­la­tion. This was good news, Gar­ci­aLopez ex­plained to Lily’s own­ers, be­cause the best ap­proach to the prob­lem was to wait about six months from when the her­nia re­oc­curred be­fore at­tempt­ing another re­pair.

“When you re­pair a her­nia, you want a very, thick fi­brous ring of scar tis­sue around the de­fect,” he says. “The thicker it is, the bet­ter able it will be to hold the new su­tures. I think that may have con­trib­uted to the first re­pair fail­ure---it was sim­ply done too soon. I told [Lily’s own­ers] we needed to wait for the scar tis­sue to form, and then we could at­tempt another re­pair.” They agreed, loaded the mare and headed back home to wait.

Silky so­lu­tion

When Lily re­turned to Tufts two months later, says Gar­cia-Lopez, “the ring of scar tis­sue around the her­nia ap­peared thick enough on ul­tra­sound to hold more su­tures.” How­ever, the vet­eri­nar­ian also of­fered the mare’s own­ers an al­ter­na­tive---to try out a new, still-ex­per­i­men­tal method of re­pair.

In hu­man medicine, plas­tic or re­con­struc­tive sur­geons may su­ture a flex­i­ble mesh into the tis­sues to help pro­vide strong sup­port for heal­ing with re­duced risk of com­pli­ca­tions. “His­tor­i­cally, polyester and polypropy­lene meshes have been used,” says Gar­cia-Lopez. “They are good and strong, but they last for­ever as a for­eign sub­stance in the body, and if an in­fec­tion de­vel­ops, you have to re­move all of it as part of the treat­ment.”

How­ever, Gar­cia-Lopez had been work­ing with a re­search group in the de­vel­op­ment of a new type of mesh made with silk. “Silk mesh is con­ducive to bring­ing new fi­brob­lasts into the area, which leads to the growth of fi­brous tis­sue,” he says. “As this is hap­pen­ing, the silk de­te­ri­o­rates, so ul­ti­mately it is re­placed by na­tive tis­sue. Treat­ing in­fec­tions doesn’t ne­ces­si­tate re­mov­ing the silk mesh, ei­ther. Silk has been around for cen­turies, ob­vi­ously, but only in the last decade or so have we known how to weave it to­gether to be strong enough for sur­gi­cal ap­pli­ca­tions such as this.”

Prior to Lily, Gar­cia-Lopez had used silk mesh in sur­gi­cal tri­als on sheep, and he had con­ducted a few pre­lim­i­nary tri­als in horses, but he hadn’t yet used it on a large and per­sis­tent her­nia. How­ever, the mare’s own­ers agreed it was worth a try, and the surgery was sched­uled for the fol­low­ing day.

With Lily fully anes­thetized and po­si­tioned on the sur­gi­cal ta­ble, Gar­cia-Lopez cut a two-inch-wide el­lip­ti­cal-shaped in­ci­sion to the right of the her­nia on her mid­line. He then care­fully sep­a­rated the mus­cu­lar lay­ers of the body wall to ex­am­ine the tis­sue around the her­nia.

“You have to take into con­sid­er­a­tion how much you’ll be able to pull the body wall back to­gether, given the strength of the area and the amount of fi­brous tis­sue you have to work with,” says Gar­cia-Lopez. By man­u­ally ma­nip­u­lat­ing the tis­sues, he was able to re­duce the size of the her­nia to about

two inches. Next, he stretched the silk mesh across the gap, an­chor­ing it within the lay­ers of mus­cle tis­sue in the ab­dom­i­nal wall. He then su­tured the outer lay­ers of skin closed and placed a tight her­nia band on the mare be­fore wak­ing her up.

“There’s al­ways a mo­ment of worry as the horse scram­bles back to its feet,” says Gar­cia-Lopez. “That can pull all your work apart im­me­di­ately.” But

be­tween the silk mesh and the her­nia belt, Lily’s her­nia re­pair re­mained strong for the three days she stayed at the clinic for con­tin­ued ob­ser­va­tion. She also re­ceived treat­ment with an­tibi­otics and anti-in­flam­ma­to­ries.

“The belt of­fers sup­port but also re­duces edema in the area,” says Gar­cia-Lopez. “If you can keep the edema down, there is less stretch­ing of the tis­sues.” Lily’s her­nia belt

re­mained in place af­ter she went home; it was re­moved only for short pe­ri­ods each day for groom­ing and ad­just­ment. The mare re­turned to Tufts for two fol­low-up ex­ams, at eight and 20 weeks af­ter her surgery.

At each visit, ul­tra­sound ex­am­i­na­tions showed that the mesh was hold­ing strong and fi­brous tis­sue was quickly form­ing around it. Ex­ter­nally, Lily’s mid­line re­mained flat and smooth, with no sign of a re­turn­ing bulge. Af­ter the sec­ond visit, the her­nia belt was re­moved for good, and the re­pair con­tin­ued hold­ing strong.

Lily went on to ful­fill her new role as a brood­mare. “We were for­tu­nate to be able to keep track of her,” says Gar­cia-Lopez. “She had at least two foals, one of which had to come into the clinic for a small prob­lem. We were able to take a close look at her then and saw no is­sues at all with her her­nia. Two foals later, she still looked great. There’s no rea­son to think it won’t hold for­ever.”

ab­dom­i­nal wallBULGE: A her­nia is the protru­sion of an or­gan or body tis­sue through a breach in the fi­brous tis­sue cov­er­ing the ab­dom­i­nal area. Her­ni­a­tion at the in­ci­sion site is a com­mon com­pli­ca­tion of colic surgery, oc­cur­ring in 10 to 20 per­cent of cases. in­testines peri­toneum ( lin­ing of the ab­domen) ab­dom­i­nal mus­cle fas­cia sub­cu­ta­neous fat skin



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