By David E. Freeman, MVB, PhD, Diplomate ACVS
Although colic surgery was considered hopeless 60 years ago, today it can save horses from devastating diseases and give them a long life, free of complications and recurrence. However, according to a nationwide study on equine health and management done in the United States in 1997, colic was second to old age as the leading cause of death in horses over 30 days of age, and ranked second and third in days of lost use and morbidity, respectively.
At least six recent studies reported that 80 to 88 percent of horses that had completed surgery of the small intestine survived to leave the hospital, which is a considerable improvement over previous reports for diseases traditionally associated with a very poor prognosis. Early referral is the most important reason for improved survival from colic surgery as well as for the reduction in postoperative complications. In a German study on 143 horses that had small intestinal surgery, survival was 75.6 percent if surgery was performed within eight hours from onset of colic, compared with 45.1 percent survival in horses that had surgery 12 hours or more after onset of colic. High on the list of other advances that can improve survival is the growth in specialty colleges in anesthesia, surgery, internal medicine and critical care, all of which have taken colic treatment and aftercare to another level.
If your horse develops colic, call your veterinarian. He or she can treat most nonsurgical colics very effectively and administer effective pain control with flunixin meglumine (Banamine) and xylazine. Although side effects of these drugs are of little clinical importance if the drugs are used appropriately, the biggest and costliest mistakes with flunixin meglumine are intramuscular injection and repeated doses at short intervals. Intramuscular injection can cause clostridial myositis, which has a very high mortality rate. Frequent doses can cause severe renal damage in dehydrated horses and can also obscure signs of pain so that it becomes impossible to detect a worsening of clinical signs and need for more appropriate therapy.
A horse with colic can be walked to prevent it from injuring itself and damaging property, but, as with medications, walking should be interrupted frequently to allow changes in comfort level to be assessed. Under no circumstances should a horse with colic be fed until your veterinarian is satisfied the problem has resolved, because food can only complicate the obstruction and its treatment. Your veterinarian might pass a stomach tube to check for accumulation of fluid under pressure in the stomach. Gallons of gastric fluid usually indicate a high obstruction, probably in the small intestine, and its removal will make the horse comfortable and reduce the risk of stomach rupture. This finding indicates that your horse should be referred to a specialty hospital.
If your horse is referred to a veterinary hospital by your own veterinarian, that means that he or she believes your horse has a more severe colic than can be managed on the farm, that your horse might need surgery or that your horse needs to be continually monitored, observed and treated. Once admitted to the hospital, several steps will be followed, the first of which is to assess your horse’s overall physical condition and degree of pain. A basic physical exam accomplishes this, and when the results are combined with information that you give about your horse and its recent and past colic episodes (history), further diagnostic tests might be needed. Usually a blood sample is taken to determine the degree of dehydration and shock.
Decision Making and First Aid
Many of the more dramatic clinical signs of severe colic caused by strangulating and inflammatory diseases in the small and large intestines are caused by endotoxin circulating in the blood (endotoxemia). Endotoxin is a component of the outer wall of gram-negative microorganisms in the intestine and it gains access to the circulation by leaking across the intestinal lining that has become damaged by a lack of blood supply, as in a twist or strangulation, or when destroyed by an inflammatory process. It is usually corrected by surgical removal of dead bowel, but it causes a profound shock that puts the horse at risk of succumbing under anesthesia. The shock caused by endotoxemia is characterized by redistribution of blood flow to critical organs, so that the intestine and less critical tissues are poorly perfused. Endotoxin is not damaging, but the body responds to it in an exaggerated fashion that generates a cascade of different chemical events that are damaging. Our goal is to control these responses and, although a variety of options are available to us, the best known and most commonly used is Banamine. Also, intravenous fluids are essential to replace water and electrolytes lost through the intestinal disease, endotoxemia, and lack of intake, and will be given for this purpose before and after surgery. Other treatments for endotoxemia are available, but they are expensive and not essential in most cases.
Among the many advances made in colic management is the improved ability to diagnose colic and even identify specific lesions before surgery in some cases. Passage of a stomach tube can remove stomach and intestinal secretions that have accumulated proximal to a small intestinal obstruction, and indicate such a lesion. A rectal examination is performed in horses of sufficient size and appropriate temperament, but can only examine an area close to the back of the abdomen. Ultrasonography has greatly facilitated the decision to perform surgery and can even identify the specific lesion in some cases. Ultrasonography also is very informative in foals and ponies, which are too small for rectal examination. A sample of peritoneal fluid can be obtained by inserting a needle in the abdomen (abdominocentesis), but is not necessary if other clinical findings indicate surgery is needed. The fluid will be bloody and contain more white blood cells and protein than normal if the horse has a segment of dead intestine, but the fluid can be normal in the early stages of intestinal injury. The greatest diagnostic challenge in some cases is to distinguish between a strangulating lesion (dead intestine) and proximal enteritis and ileal impaction (southeast USA). If all the tests cannot guide us, and the horse has most of the signs of a surgical lesion, remember that surgery itself is a diagnostic procedure. Hence the term, exploratory celiotomy (opening into the abdominal cavity).
For some diseases that we corrected with surgery in the past, surgery might not even be required today. For example, if the colon becomes draped over the ligament from the spleen to the kidney (entrapment of the colon over the nephrosplenic ligament), this can be managed by rolling the anesthetized horse or by infusion of phenylephrine to shrink the spleen, followed by gentle exercise. The purpose of these treatments is to dislodge the colon off the top of the spleen where the ligament attaches.
Once the decision has been made to do surgery, the actual procedure chosen, its degree of difficulty, and its success rate, will all be determined by the lesion causing colic. Your horse will first be anesthetized by the most modern techniques available, and its physiologic wellbeing is monitored continuously while under anesthesia, with special attention to maintaining normal heart and lung function. The abdomen is then opened through an incision along the ventral body wall, because this allows access to most of the abdomen. Unfortunately the surgeon can only take out and visually examine certain parts of the horse’s intestinal tract, whereas other parts are only accessible to blind palpation. These same parts cannot be accessed for surgical removal or opening if this is needed, although techniques have been developed to circumvent this problem in some cases.
If the intestine is blocked by food material or sand, and this can be broken down by external massage of the bowel wall, it will be milked into the next segment to get it started down the gastrointestinal tract. If a rock has formed in the large intestine, which is called an enterolith, this will have to be removed through an incision in the intestinal wall, as will all other large immovable obstructions, regardless of composition. This is usually a very successful procedure, despite the need to open into the bowel. If intestine has lost its blood supply (twist or strangulated by an entrapment within the abdomen by various hernias, bands and lipomas), the surgeon will correct the strangulation and determine if the bowel needs to be resected. If it is resected or removed, one of various types of anastomoses will be needed to restore intestinal continuity, depending on the site of the lesion and the surgeon’s preference.
Large colon volvulus or torsion is a common cause of colic, especially in broodmares, but presents a unique challenge, because once it is diagnosed in a young broodmare, the risk of recurrence is high. Colon resection is the treatment of choice if the colon is dead after the torsion, and of course this will also prevent recurrence. But what if the colon is viable and the horse had two incidences of torsion in one year? Surgeons wrestle with the choice of colopexy versus colon resection in these horses, and the final decision comes down to the surgeon’s preference. Colopexy involves suturing the colon to the body wall to create a permanent attachment (adhesion) that can prevent displacement in most cases. Despite being an apparently more aggressive procedure than colopexy, large colon resection is well tolerated and safe and will allow horses to return to full use, without digestive upsets.
Depending on the procedure, the horse will pass through a critical period of three to six days after surgery, in which most early complications become evident. For example, correction of a nonstrangulating displacement of the large colon will be followed typically by a very rapid recovery, whereas recovery after large colon volvulus (twist or torsion) is slow and complicated. Prognosis tends to be poorest for a horse that requires small intestinal resection followed by anastomosis of the small intestine to the cecum, compared with anastomosis of small intestine to small intestine.
When an anastomosis is performed, two ends of intestine are joined together by sutures to restore intestinal continuity and function. But sometimes the anastomosis does not work, because the sutures somewhat restrict its ability to expand. Alternatively, the normal signals that pass through intestinal muscles and nerves are interrupted and the intestine on one side of the anastomosis is out of sync with the segment on the other side, so they fail to push food material through in an organized, coordinated sequence. This causes a mechanical obstruction or blockage. On the other hand, postoperative ileus (POI) is characterized by total paralysis of the remaining intestine without any mechanical obstruction. Because horses cannot vomit, the fluid that fails to move through the intestine because of paralysis or mechanical obstruction backs up into the stomach, from where it must be drained through a stomach tube. POI occurs in 10 percent to 55.6 percent of horses after small intestinal surgery and is very rare after large intestinal surgery. More recent studies document a decline in this complication and fewer deaths from it. Almost all horses will recover with good nursing care and fluid therapy to offset the fluids lost through draining the stomach. Drugs used to stimulate motility are rarely effective.
Adhesions have been documented in 6 percent to 26 percent of horses after small intestinal surgery, with a marked decline in prevalence in recent reports. They are very rare after large intestinal surgery. Adhesions usually cause problems in the first two months after surgery, and the risk diminishes after 6 months. Adhesions are a response to disease and surgery and represent an exaggerated attempt to heal through erratic and unpredictable scar formation. The surface of the traumatized intestinal wall adheres to the wall of a nearby segment of intestine and the point of adhesion tethers the two segments together. If this tether is restrictive, one segment of small intestine will become obstructed much like a kinked garden hose that is suddenly filled. Factors that could contribute to adhesions are ischemia, suture material and handling the bowel wall (inevitable during surgery). Surgeons do all they can to prevent adhesions and can use drugs and various topical preparations to reduce this risk. In the author’s opinion, horses are not particularly prone to forming adhesions in the small intestine, but are very susceptible to obstruction from them.
Although removal of almost 95 percent of the large colon is well tolerated and does not require nutritional adjustment, removal of 70 percent or more of small intestine can lead to failure to absorb nutrients (malabsorption), which can cause a fatal weight loss syndrome similar to starvation. Although these horses eat, they lack sufficient length of small intestine to digest and absorb nutrients, despite imaginative dietary changes. Therefore, surgeons might recommend humane euthanasia when enough small intestine has to be removed to place the horse at risk of malabsorption.
Occasionally, a repeat exploratory may have to be considered if the result of the first surgery was unsatisfactory. The interval between the first and second surgeries could be as short as 24 hours. Repeat surgery can be required for 12 percent to 27 percent of small intestinal surgery, which can be explained by the sensitivity of the small intestine to the primary problem, the surgical procedure required to correct it, and altered motility. Remember that the first surgery is performed as an emergency on a very sick horse, and the intestine might not respond as expected. Although a second surgery seems like a daunting prospect, a horse that needs a second surgery will not survive without it. Also, the response is usually quite favorable, and the cost of a second surgery could be considerably less than the delay of continued medical treatment if surgery were needed instead.
Aftercare for a horse that has had colic surgery is designed to prevent complications and to restore gastrointestinal function to normal as quickly as possible. The latter is achieved by feeding horses as soon as the surgeon considers it safe to do so, somewhere between 18 to 36 hours after surgery if the horse can tolerate it. The author prefers to start with good quality alfalfa hay, because horses prefer this over mashes, and it stimulates normal intestinal function effectively, especially in the colon where hay will promote normal colonic fermentation and offset the risk of colitis. We start slowly to allow a gradual return to full intake without stressing the bowel in the process.
We continue with fluid therapy as before surgery, but usually at a slower rate to accommodate the reduced need. Fluid therapy will cease when the horse appears to be well hydrated clinically and, by laboratory results, he can consume water without any discomfort and there are no signs of complications that would cause fluid loss (postoperative ileus, obstruction, endotoxemia and diarrhea). We will also give the recommended dose of Banamine daily for at least 2 days to reduce postoperative discomfort and any postoperative inflammation that could cause adhesions.
We administer antibiotics to horses starting before and continuing for 2 to 3 days after surgery or longer, depending on surgeon preference. The purpose of antibiotics is to reduce or eliminate bacteria from the abdominal incision, where they cause infection, and from the wall of the intestine, where they cause inflammation and adhesions. Disadvantages of antibiotics are that they can induce bacterial resistance against them and some antibiotics have been implicated in diarrhea (colitis) in horses. The latter is caused by death of the normal populations of bacteria in the colon, which allows the disease-causing strains to flourish in the absence of competition. Therefore, we aim to discontinue these drugs as soon as we can after surgery.
Recovery at Home
About 5 to 8 days or so after surgery, if your horse is doing well, we suggest that you take him home to return him quickly to a familiar environment that allows for a calmer and healthier convalescent period. Traveling is well tolerated at this stage and a healthy incision in the body wall should not be jeopardized by transport. The most critical part is to keep the horse quiet and stall confined for at least 1 month. If your horse develops an incisional problem (infection or incisional breakdown), then a longer period in a stall might be needed. Always consult with the surgeon if you have questions about this. Feed your horse whatever the surgeon recommends, usually a high forage diet, and avoid or reduce grain because this can cause your horse to become overactive and intolerant of confinement. After the first week at home has passed and your horse has settled in, a little handwalking would be recommended for 10 to 15 minutes, once to three times a day. He can graze during these periods.
After the first month has passed, you can turn your horse out in a small paddock on his own and where he will not be distracted by other horses in nearby paddocks. He should be on a handwalking program first to allow him to adjust to being outside and might even need to be sedated on the first day. Start with turnout times of half an hour at first, then increase up to 12 hours or so a day within the first week. The horse might do better if stalled at night because he can then be quiet during a time when he is not under observation. After this month has passed, your horse can resume normal activity, but slowly at first and probably after you have received the go ahead from your veterinarian. Remember, this program is one example and could be modified according to surgeon’s preference or your horse’s progress.
A broodmare that had colic surgery in spring might be a candidate for breeding shortly after surgery. If the breed allows artificial insemination, the mare can be handled as with any broodmare and your veterinarian can work with you on selecting the suitable insemination date. If the mare is a thoroughbred and the foal is to be registered with the Jockey Club, natural cover is required and you might want to wait 6 to 8 weeks after surgery or select a date that your surgeon and your own veterinarian would consider suitable based on the progress of healing in the body wall. The same applies to a stallion, whether he needs to breed by natural cover or be collected off a dummy. Mares can foal without risk of incisional damage at any time after colic surgery including the day after surgery. Your surgeon might wish to use a belly bandage or additional suture methods for such mares during anesthetic recovery, because the weight of a term uterus could be additional stress on the repair.
You should check your horse’s temperature daily at home, remembering that normal is 99.5ºF to 100.5 ºF, and do so at the same time of day because the afternoon temperature is usually higher than the morning temperature. The surgeon can close the skin by a variety of methods such as absorbable suture, metal clips and nonabsorbable (or permanent) suture; the last two types should be removed about 10 to 14 days after surgery, the first will disappear on its own. Examine the suture line by inspection and avoid palpating it for sensitivity. Firstly, most horses will be sensitive along the skin incision regardless of whether or not it is infected, and, secondly, palpation can place you in a dangerous position if the horse kicks. See below for what to expect with the incision.
What to Expect
Know what to expect after your horse arrives home because your horse will undergo some changes that are predictable, usually benign, and almost always temporary:
• Your horse might be quieter than usual, but this is a typical response to stress and surgery.
• Your horse might lose weight. This is usually not serious, unless the horse is showing other abnormal signs such as depression and inappetance or if your surgeon discussed the possibility that so much small intestine was removed that he or she is concerned about malabsorption as a result. In most horses, the weight loss is caused by the stress of recent events, decreased food intake because of restricted grain intake, consumption of energy and body protein by tissue repair and wound healing, and loss of muscle mass brought on by inactivity. Of course, if you become concerned, consult your veterinarian. Also, remember that each horse is an individual, and some will remain below normal body weight for months, while others will actually gain weight. The latter is most likely after surgery for a chronic disease, but not always.
• Your horse might have more bouts of colic. The severity is the critical element here because some mild bouts might not be unusual, although definitely abnormal and of critical importance. Contact your own veterinarian and the surgeon when you become concerned and certainly keep a log of dates, times of day, relationship to feeding and your opinion of severity. Occasional bouts of colic are not unusual during the first 6 months after small intestinal resection and could signify transient or permanent problems with the anastomosis or with adhesions. Hard and fast numbers for typical cases of recurrent bouts are impossible to give, but one to three bouts of mild colic in a 6 month period might not be that unusual after a complicated intestinal surgery. The nature of the original problem and the type of surgery are the most critical factors in determining how serious this problem is. Whereas most horses will have a life free of colic after surgery, others might have an idiosyncratic predisposition for colic.
• Incisional swelling is almost certain after colic surgery and the severity can reach alarming proportions as a raised flat plaque with sharp edges that can persist for weeks in rare instances without actually signifying a problem. Call your surgeon or have your veterinarian check this if you are concerned. The cause could be as simple as a reaction to buried suture material, which will be absorbed over one to three months. Swelling accompanied by drainage, fever and depression signifies infection. Incisional infection can develop in 32 to 36 percent of horses that have intestinal surgery, but most infections fortunately respond well to treatment by gentle daily cleaning with warm water and dilute antiseptic and do not interfere with healing.
• After two to three months from surgery, it is not unusual to feel small weak spots in the body wall along the original suture line. These are well tolerated, even in athletes and broodmares. Large hernias that involve part or all of the incision can be repaired by suture closure or by inserting a plastic mesh. These are expensive treatments, although usually successful. Untreated hernias are rarely life-threatening, and many can be left unrepaired without any adverse effects, even during pregnancy. The decision to repair and the method chosen will vary from one case to another, and should be determined by consultation with an experienced surgeon. The most important issue for you as owner is to be aware that hernias can develop in months (2 to 4) after the surgery in a body wall that was apparently healing well to that point, and definitely are more likely after an infected incision. Approximately 6 percent of horses develop some form of hernia after colic surgery.
• A big concern is the longterm effect of colic surgery on the horse. Will he be able to live a normal life, will he be able to race or perform? Can a mare have normal foals? The answer to these questions is yes, especially if the horse survives the short term at the rate of progress expected for the lesion. There are numerous examples of horses involved in strenuous activities that performed to full potential after colic surgery, even winning races like the Kentucky Derby.
• Life expectancy after colic surgery is definitely improving. The pattern of survival after colic surgery follows three distinct phases, with most deaths during the first 10 postoperative days, when the horse is still hospitalized. The next phase is within 100 days after surgery, and 69 percent of all postoperative deaths occur by this stage. The death rate declines slowly after that, so the risk of death from surgery-related problems diminishes markedly 12 months from the date of surgery.
Prevention of Colic
Prevention of colic will always be difficult until we understand more about the disease itself and its varied causes. Epidemiologic studies have taught us that increasing time grazing, feeding more good quality roughage and fewer concentrates, and minimizing management changes can significantly decrease incidence of colic. Recognized risk factors are ileal impaction with feeding coastal Bermuda grass hay, stall confinement with gastric ulceration, and cribbing with recurrent colic and strangulation of small intestine in the epiploic foramen. Constant access to fresh water is probably critical to prevention of impactions caused by feed material, and the greatest need for water is after eating. Horse related factors cannot be altered, but do provide information that is of diagnostic information, such as standardbreds, tennessee walking horses, and american saddlebreds for inguinal hernias, american miniature horses for fecaliths in the small colon, thoroughbreds for strangulation in the epiploic foramen, ponies, quarter horses, and arabians over 10 years of age for strangulation by lipomas, and postpartum brood mares for large colon volvulus and segmental ischemia of the small colon. A disease of growing importance and attributed to phenylbutazone sensitivity is right dorsal colitis, characterized by inflammation, ulceration, necrosis, and fibrosis of the terminal part of the large colon, which can cause local discomfort and recurrent impactions.
One of the greatest success stories of recent decades is the decrease in prevalence of S. vulgaris in regularly dewormed horses and on most well managed farms. However, in their wake, other parasites have been implicated in different types of colic, and these are tapeworms (intussusceptions and ileal impactions), ascarids (small intestinal obstruction in young horses), and encysted cyathostomes (diarrhea, colic, and ill thrift). We are now becoming aware of resistance to ivermectin with small strongyles and ascarids. We have approved dewormer combinations with praziquantel as the active ingredient against tapeworms. Apply worming programs intelligently by avoiding the rotation programs of the past, and use fecal egg counts to monitor the response to your program.
Above all else, be a smart horse owner. Minimize risk factors that can predispose your horse to colic. Observe your horse frequently, be aware of its behavior patterns, and be sensitive to subtle changes. Be prepared by always having a trailer available, critical phone numbers at hand, and directions to the nearest facility. If your horse needs surgery, make sure you understand what is involved. Many owners tend to “follow along” and nod in response to information the veterinarian or surgeon gives, which is understandable under the stress of the moment, but is not enough. Ask questions and make sure you comprehend. Be as patient and cooperative as you can under the circumstances, and try to create a positive working relationship with the doctor to whom you are entrusting your horse’s health. Avoid any behavior that can be distracting to the hospital’s primary mission, and that is to save your horse’s life. Work within the hospital’s policies for visiting hours and payment schedules. Remember that the outcome is determined by teamwork, and you are an integral part of that team, along with your own veterinarian and the staff and surgeons at the hospital. Stay educated, but keep an open mind about what you read, because there are many differences in opinion on any subject, information changes rapidly, we do not have all the answers, and some information that is freely distributed simply lacks scientific merit.
Despite the good news, the very bad news is that colic surgery is expensive, and the cost can prove the limiting factor in all too many cases. In most clinics in the U.S., cost of colic surgery typically exceeds $4,000, which makes it the second most expensive surgery after repair of long bone fracture. Although costs of surgery and anesthesia can be standardized to some extent, the cost of aftercare is less predictable and can be altered considerably by development of complications. We all recognize the need to strike a balance between a fair cost for a demanding and complicated surgery and making colic surgery affordable to more horse owners. Steps toward these goals are early referral for surgery, doing surgery before irreversible changes have developed in the intestine, selective use of treatments with known efficacy, improved disease prevention, and education for all involved on management of affected horses.