Rectal Tears in the Horse

A rectal tear is a tear through one or more of the layers of the rectal wall. These tears can be superficial, deeper and through the inner layer, or penetrate through all layers of tissue.

Rectal tears may occur as a result of a breeding accident, or due to other trauma, but the most common cause of a rectal tear is the rectal exam. The internal examination or rectal exam, is an essential tool for diagnosis of diseases within the abdominal cavity and for breeding management. The rectal examination is used as a part of the physical examination in colic, to determine if there is a displacement, twist, or distension of the intestines, to try to determine what portion of the intestines are involved. In this regard, the rectal exam is important for determining the need for surgery. It is also used to determine if there are masses (such as an abscess or tumours) in the abdominal cavity and to determine whether a mare is ready to breed, whether a mare is pregnant, and, at later stages of the pregnancy, whether the fetus is alive.

Rectal tears occur just as commonly to inexperienced practitioners as to experienced practitioners. The severity and seriousness of a rectal tear will depend on the depth and length of the tear. A simple abrasion – a tear that only extends to the first layer of tissue – may even go unnoticed. A deep tear, or one that goes through all layers of tissue, can be life-threatening. Tears that occur closer to the abdominal cavity are also more dangerous.

Predisposing factors concerning the horse include obesity, excessive movement of the horse during rectal exam, and dehydration (the latter two are common with a colicky horse). Rectal tears may be more common in certain breeds, such as Arabians, but this is not clearly proven.

Young, nervous horses and aged horses seem to be more prone to rectal tears, as do stallions and geldings due to their smaller pelvic canal.

What to Watch For

• Blood on the veterinarian’s sleeve immediately after rectal examination
• Signs of abdominal discomfort after a rectal examination
• Your horse may roll, paw, repeatedly go up and down, or look at his sides
• Signs of shock after a rectal examination: Your horse may be shaky, sweat and have a very high heart rate
• Blood at the anus or on the hind legs or tail within 12 hours after rectal examination

Veterinary Care

• As soon as your veterinarian suspects that there is a rectal tear, he or she will inform you of the accident, and then will take emergency steps to deal with the problem. Remember, rectal tears are a recognized complication of any rectal exam, and cannot always be avoided.
• Your veterinarian will usually choose to sedate the horse heavily before proceeding further, then perform a bare-handed rectal exam in order to determine exactly where the tear is and how deep it is.
• If the tear is superficial, then it can often be managed quite easily. Your veterinarian will often choose to place your horse on broad-spectrum antibiotics, and will usually give mineral oil using a nasogastric tube in order to soften the feces. Your horse may do better with low fiber feeds for several days to a week. This type of tear usually heals without any major complications.
• Tears that extend through all but the last layer of the tissue of the rectum can be life-threatening. If the abdominal cavity becomes contaminated the horse has a very poor prognosis.
• In the case of a deep tear, the horse should receive emergency treatment at the farm. This will include broad spectrum antibiotics, a tetanus booster, and in some cases an epidural to numb the area and prevent the horse from straining. The horse should be transported as quickly as possible to a referral institution for surgical repair.

Repair of a rectal tear must be done in two stages; consequently it is both time-consuming and expensive. The first surgery is a colostomy, in which an alternative area for defecation is created in the horse’s flank. This allows the tear to heal on its own. The second surgery reconnects the colostomy to the rectum.

Even with appropriate emergency treatment, a horse with a deep rectal tear has a guarded prognosis.

Home Care

If your horse has sustained a minor, superficial tear, then there is a little in the way of home care that must be done. It is important to follow your veterinarian’s directions for giving antibiotics and keeping the manure soft. You should watch carefully for any signs of hard manure, difficulty or straining with defecation, or signs of colic.

When your horse is sent home after the first surgery, he will need food that helps to maintain soft, moist feces. This may include green grass, lots of fresh water, and very well-soaked hay.

Preventative Care

Although the majority of rectal tears probably cannot be prevented, there are a few things that you can do. Make sure that your horse is very well-restrained and possibly sedated for any rectal exam.

The extent of your precautions very much depend on the particular horse. An experienced broodmare is at very low risk and is unlikely to need any sedation, but a young stallion is at high risk for a rectal tear, and probably needs not only sedation but also active restraint such as a twitch.

Rectal Anatomy

The rectum of the horse constitutes the last portion of the gastrointestinal system. It extends 30 to 40 inches from the anus going toward the mouth. There are two different parts of the rectum – the peritoneal part, and the retroperitoneal portion. The peritoneal portion lies closer to the mouth, and the retroperitoneal portion lies closer to the anus. The peritoneal cavity contains the internal organs of the abdomen within a closely fitting sac-like structure. The retroperitoneum lies outside of the peritoneal cavity and does not communicate with it.

A deep tear that involves the peritoneal portion is likely to cause contamination of the peritoneum, and consequent peritonitis, or infection of the peritoneum. Rapid surgical management is necessary in order to save the horse, and even with the best of treatment, the horse may die. A tear, even a deep one, that involves the retroperitoneal portion, may sometimes be successfully managed medically, and may not need surgery.

The rectum has four layers:

• The mucosa – the portion that lines the inside of the rectum
• The muscularis – a thin muscular portion
• The submucosa – the portion that lies between the muscularis and the mucosa
• The serosa – the portion that comes into contact with the peritoneal cavity and is the outermost layer

Classification of Rectal Tears

• A Grade I rectal tear is superficial and causes disruption of the mucosal layer only.
• A grade II rectal tear involves only the muscularis. This is often an incidental finding, and feels like a small, smooth divot in the rectal wall. The mucosal layer is intact. This is thought to be the consequence of a healed rectal tear during the early years of a horse’s life.
• A grade III tear involves all layers except the serosa. However, with only the serosa intact, there is now only a very thin layer between the rectal contents (manure) and the peritoneal cavity. Even if the serosa stays intact, the horse will develop peritonitis because bacteria and their products can cross this very thin layer into the peritoneal cavity.
• A grade IV tear is one that involves all layers of the rectum. This means that there is now no barrier between the rectum and the peritoneum. Manure with all its bacteria and other contaminants now spills directly into the peritoneal cavity. Peritonitis quickly ensues.

Causes of Rectal Tears

Studies show that rectal tears have little if anything to do with the capabilities or experience of the person performing the rectal examination. The rectal tear is thought to be due not to the practitioner ‘poking a hole’ in the rectum, but due to the horse tightening and contracting the rectum around the veterinarian’s hand. The rectum then essentially splits around the hand, rather than the hand forcibly causing the tear.

Horses that are poorly restrained during rectal examinations are more likely to develop rectal tears – so if your veterinarian wants to sedate or twitch your horse during an examination, you should not protest.

In one study, researchers tried to create rectal tears in order to evaluate special instruments for repairing the tears. Much to their surprise, no matter how hard they tried, they couldn’t cause tears. This indicates that horses that suffer rectal tears probably have some underlying defect in the tissue of the rectum that predisposes them to develop rectal tears.

It’s true that horses that have small pelvic girdles are more likely to get rectal tears. This would include young horses of either sex, stallions and geldings. Horses that are nervous and anxious are also more likely to develop rectal tears because they are more likely to contract the rectum around the veterinarian’s hand.

Anything that makes the rectal tissue weaker and less able to heal will make it more likely that a horse will develop a rectal tear. One disease that older horses are likely to have is called Equine Cushing’s Disease. One of the consequences of this disease is excessive production of corticosteroids by the horse’s body, which results in poor tissue healing and weak tissue structure. Even if an older horse does not have Equine Cushing’s Disease, they still have poorer tissue healing, and weaker tissue than a younger horse. Malnourished horses or chronically ill horses may also have weaker tissue and poorer tissue healing than healthy horses.

Occasionally, a rectal tear occurs as a breeding accident, with the rectal tear as a result of intromission attempted in the rectum.

In a few cases, rectal tears have occurred as a result of a foreign body – either something that the horse ingested or backed into, or as a result of cruelty by humans. In a few rare cases, horses with Cushing’s disease have developed rectal tears secondary to small colon and rectal impactions. The rectal tissue is so weak that as the horse strains and pushes against the impaction the rectum splits around the impaction, creating a rectal tear.

Emergency Care and Diagnosis In-depth

In the majority of cases, when the rectal tear occurs as a result of a rectal examination, the veterinarian knows right away that the tear has occurred since there will usually be blood on the rectal examination sleeve. Any time a veterinarian sees blood on his sleeve after a rectal examination, he should immediately suspect the worst – a Grade III or IV rectal tear. It is of vital importance to determine right away where and how deep the tear is.

• The veterinarian will usually sedate the horse heavily in order to allow another rectal examination without any straining by the horse.
• Often, the veterinarian will also infuse the horse’s rectum with lidocaine or some other local anesthetic. This will numb the area, and help to prevent the horse from straining.
• In some cases, the veterinarian will choose to give the horse an epidural. The epidural is given in the epidural space that surrounds the nerves at the end of the spinal cord. This not only numbs the rectum, but also paralyzes it temporarily. This is the most effective way to prevent the horse from straining.
• The veterinarian will then remove her sleeve, and use her bare hand to investigate the tear. This is because the bare hand is much more sensitive than even a very thin glove, and is better suited for determining the location and grade of tear.
• If your veterinarian has a long endoscope, she may choose to do a proctoscopy to visualize the tear.
• If the tear is a Grade I or Grade II, then your veterinarian will most likely choose to manage the tear on the farm. A mucosal (Grade I) tear usually heals on its own with very minimal management. The veterinarian usually chooses to give broad spectrum antibiotics for 5 to 7 days, administers a tetanus booster, and gives mineral oil using a nasogastric tube in order to produce soft manure. Your veterinarian checks your horse’s progress every few days until the tear is healed.
• If the tear is a Grade III or Grade IV, then your veterinarian further prepares the horse for referral to a surgical facility. He administers intravenous or intramuscular broad spectrum antibiotics and gives the horse a tetanus booster.
• If the veterinarian has not yet performed an epidural, then he should do so now. Your veterinarian will evacuate the horse’s rectum thoroughly, and then may pack the rectum to prevent further contamination from occurring. It is very important to have an effective epidural working before this step, otherwise it will worsen the tear.
• If your horse has a long ride to the surgical facility, your veterinarian will often choose to give intravenous fluids prior to the ride.
• In the case of a grade III or IV tear, your veterinarian will avoid giving mineral oil, as it will be impossible to repair the situation if the mineral oil contaminates the peritoneal cavity.

Further Diagnostics

Although rectal tears caused by a rectal examination are usually immediately apparent, there are occasions when they may go undetected initially.

The veterinarian may suspect a rectal tear if a horse shows signs of colic or shock within hours after a rectal examination. The signs of shock include: high heart rate, pale or brick red mucous membranes, shakiness, collapse, high respiratory rest, increased respiratory effort and cold extremities. The horse may sweat profusely.

• At the surgical facility, other diagnostics may include:
• A complete blood count. The complete blood count (CBC) helps the veterinarian to determine how severe the infection and inflammation is. In the case of gross contamination of the peritoneal cavity, the white cell count will often be markedly low (leukopenia).
• A chemistry profile lets your veterinarian determine if there are problems with the kidney secondary to dehydration and shock.
• The blood gas allows the veterinarian to determine if the horse’s blood is too acidic – usually due to the production of lactic acid. When a horse is in shock, there is poor perfusion to much of the body – meaning that the blood doesn’t get to all the areas that need it. The body starts to use anaerobic metabolism (meaning without oxygen), and produces lactic acid. Overly acidic blood can make an individual very sick.
• The abdominocentesis allows the veterinarian to sample the fluid that surrounds the intestines. If there is a grade IV tear, then the peritoneal fluid then there will be plant material, bacteria, and protozoa in the peritoneal fluid. If there is a grade III tear, there will be high numbers of cells and protein in the peritoneal fluid, but there should not be any plant fibers. With a grade I or II tear, there should not be important changes in the peritoneal fluid.

Surgical Treatment

• Immediate repair. If the tear is close enough to the anus, then there is the possibility of repairing the tear while the horse is standing. Special instrumentation allows the surgeon to access the tear directly, and do a full repair. Unfortunately, the tear is frequently too far from the anus, and cannot be repaired directly.
• Colostomy. The most common surgical technique involves a colostomy and subsequent revision of the colostomy. Both require general anesthesia and a reasonably long surgery. In most facilities each surgery will cost the equivalent of a colic surgery – thus the financial investment is considerable.

With a colostomy, the small colon is transected ahead of the rectal tear. It is then attached to the flank of the horse, so that the horse temporarily defecates through its side. The rectal tear is allowed to heal on its own within the abdomen.

During the surgery to revise the colostomy, the small intestine and rectum are reconnected.

In the time between the two surgeries and for some time after the surgical revision, the manure must be kept moist so that the horse does not strain against it. The opening through the flank with a colostomy is also often smaller than the normal opening, and does not have the same flexibility, so it is more difficult than normal for the horse to defecate.

Complications of Surgery

• Even with prompt surgical treatment, peritonitis may be too severe, and the horse may die of shock and sepsis ( this refers to the byproducts of bacterial infection within the bloodstream).
• As with any surgery, the horse may have difficulty in recovery, or may have difficulties secondary to anesthesia and the problems inherent in anesthetizing such a large animal.
• There is always a possibility that the incision may dehisce, or come apart. This can, obviously, be catastrophic.
• The anastomosis, or place where the intestine is joined to the skin for the colostomy, or two pieces of intestine are rejoined, as when the colostomy is revised, may either dehisce or become strictured. In the latter situation, the horse develops a severe impaction where the manure was not able to pass through the intestinal tract.

Your horse will probably spend at least 7 to 14 days in the hospital with each surgery. Optimal treatment requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your horse appears to be worsening or is not improving as rapidly as expected.

After your horse is sent home, your veterinarian will probably plan to come by for a check on your horse every few days at first, and then every few weeks.

It may be necessary to perform multiple CBCs to evaluate the extent of inflammation in your horse’s abdomen.

Any signs of straining while your horse is defecating should prompt an immediate call to your veterinarian. Any signs of colic should prompt an immediate call to your veterinarian. Observe your horse for normal manure production. Scant, dry manure is a signal that your horse is not drinking enough water. You should call your veterinarian, and should do what you can to encourage your horse to drink. It is important to have fresh, clean water and a salt block available at all times.

Your veterinarian may need to give your horse mineral oil with a nasogastric tube on a frequent basis in order to keep the manure soft.

Your horse may be on antibiotics for quite a while even when he is back at the stable. It is very important to make sure that your horse receives all the recommended antibiotics, and that he gets them at the right frequency and in the right amount. The best antibiotic in the world will do no good at all if it is left as a heap of powder in the bottom of the feed bin. If your horse is a picky eater, it may be necessary to give the antibiotic as a paste. Alternatively, you may need to give your horse intramuscular injections.