Other Common Emergencies in Horses

Intraluminal esophageal obstruction is a common emergency in horses. The most frequent sites of obstruction are the proximal esophagus and just cranial to the thoracic inlet.

Predisposing factors include the following:

• bolting feed

• poor dentition

• recent sedation

• poor feed quality or ingestion of inappropriate treats or nonfood items

• recent feed changes

• dehydration

Clinical signs of esophageal obstruction in horses result from an inability to swallow saliva, water, or feed, which pools in the pharynx and then exits through the nostrils. Frothy nasal discharge, often containing feed material, occurs along with coughing due to aspiration into the trachea and lungs.

The horse can be in obvious distress, showing clinical signs similar to abdominal pain or colic, and can be difficult to handle. Chronic obstruction can result in severe dehydration and pleuropneumonia.

Typical clinical signs include the following:

• nasal discharge containing saliva and feed material

• hypersalivation

• coughing

• retching

• signs mimicking abdominal pain (eg, rolling, kicking at abdomen)

• frequent attempts to swallow

• Physical examination

• Nasoesophageal intubation

• Endoscopic, radiographic, and/or ultrasonographic examination

Esophageal obstruction is identified by palpation of a foreign body in the neck, passage of a nasogastric tube, or endoscopic examination. In refractory cases, radiography or contrast radiography might be needed, particularly if a foreign body, stricture, diverticulum, or esophageal rupture is suspected. Ultrasonography can help identify thoracic changes consistent with aspiration of feed.

• Sedation

• Antispasmodics

• Nasogastric intubation and lavage

• Antimicrobials

Feed and water should be withheld until esophageal obstruction is resolved. Acute, simple obstructions can be treated with sedation, which promotes relaxation of the esophageal musculature. An alpha-2 agonist such as xylazine or detomidine provides good skeletal muscle relaxation. Esophageal obstruction often resolves within 1 hour after administration of a sedative and/or a muscle relaxant.

Nasogastric intubation often speeds up the process by gently pushing the obstruction to the stomach. If the horse is dehydrated, IV fluids can also help resolve the obstruction.

If the obstruction has not resolved within approximately 1 hour after sedation, or if choke lasts > 2–3 hours, the horse should be sedated heavily so that its head can drop for esophageal lavage. A nasogastric tube is passed, and gentle lavage with water is performed to flush the obstruction from the esophagus and allow a nasogastric tube to be passed to the stomach.

Mineral oil should never be administered to horses with an esophageal obstruction because of the risk of lipid aspiration pneumonia. An esophageal lavage tube (a nasogastric tube with a cuff) can be useful to help resolve the obstruction and decrease feed aspiration into the lungs. Alternatively, a cuffed endotracheal tube can be passed through the nasal passages and into the esophagus, and a smaller nasogastric tube passed through the endotracheal tube can be used for lavage.

Lavage can be repeated intermittently until the obstruction is resolved and, in refractory cases, can be aided by general anesthesia, which increases relaxation of the esophageal musculature. If lavage is unsuccessful, endoscopic examination can help identify the obstruction and facilitate manual removal with endoscopic forceps.

After the obstruction has been relieved, endoscopy can be performed to evaluate the esophageal mucosa. Endoscopic examination is indicated in more complicated cases to identify the extent of esophageal injury. Circumferential ulceration of the esophageal mucosa (see endoscopic image) can predispose the horse to stricture formation and lead to recurrence of obstruction.

Esophagus, endoscopic image, horse

Image

Courtesy of Dr. Amelia Munsterman.

Horses with esophageal obstruction are at risk of recurrence in the 2–4 weeks after the initial event because of mucosal edema, even without visible esophageal damage. Feeding slurried pellets or grass during convalescence can prevent recurrence. In horses with dental disease, dental prophylaxis is also recommended to improve mastication.

When the esophagus has been damaged, constriction or narrowing peaks at 30 days after the obstruction; often, however, the condition resolves as the stricture remodels over time. Before attempts are made to resolve a potential stricture surgically, the horse should be managed medically with dietary modification for 60 days to enable remodeling of scar tissue. The condition might resolve during this time without further intervention.

To prevent or treat aspiration pneumonia in horses after esophageal obstruction, prophylactic broad-spectrum antimicrobials are administered along with anti-inflammatory drugs and appropriate tetanus prophylaxis. Sucralfate (20–40 mg/kg, PO, every 6–8 hours until mucosal healing is complete) can facilitate healing of esophageal ulceration after the obstruction has been cleared.

Rectal tears are classified into four grades based on the number of layers involved.

• Grade I involves the mucosa and submucosa only.

• Grade II involves the muscularis only, with a mucosal-submucosal hernia.

• Grade III involves the mucosa, submucosa, and muscularis, leaving the serosal layer intact.

• Grade IV involves all layers of the rectum, including the serosa.

Grade III tears are further classified on the basis of location: grade IIIa tears leave the visceral peritoneum intact; grade IIIb tears are located dorsally in the rectal mesentery.

Most tears resulting from rectal palpation are located dorsally and extend into the mesocolon. Retroperitoneal tears are rare. Fecal contamination often occurs with grade IV tears; however, bacterial translocation and peritonitis is possible with grade III tears as well. Also see the discussion of rectal tears in Diseases of the Rectum and Anus.

Rectal tears are usually associated with transrectal palpation for evaluation of colic or assessment of the reproductive tract. Other causes include the introduction of foreign objects into the rectum and breeding accidents. Some rectal tears are considered idiopathic.

• Rectal palpation

• Endoscopic examination

A rectal tear is suspected when there is sudden loss of resistance during palpation and when a copious amount of fresh blood is present on the rectal sleeve. Blood-tinged mucus usually indicates mucosal irritation only. If a tear is suspected in a horse, the severity should be immediately assessed and measures taken to initiate treatment or referral.

The horse should be sedated for assessment of a possible rectal tear, and an epidural should be performed to decrease straining against palpation. N-butylscopolammonium bromide (0.3 mg/kg, IV, slowly) can be administered to decrease peristalsis in the small colon and rectum. A lidocaine enema can also decrease muscle tone. A speculum should not be used during examination, because it can worsen the tear. Digital palpation (preferably bare-handed) is then carefully performed.

A thin flap of tissue indicates a tear through only the mucosa. If a large cavity with a thin membrane is noted, a grade III tear is present. If intestine can be palpated, the tear is grade IV. Visual confirmation and colonoscopy/rectal endoscopy can aid a more thorough diagnosis (see colonoscopic image).

Rectal tear, colonoscopic image, horse

Image

Courtesy of Dr. Amelia Munsterman.

• Dietary management

• Antimicrobials and anti-inflammatories

• Tetanus prophylaxis

• Measures to minimize the risk of laminitis

• Surgery

Grade I and II tears can be medically managed with broad-spectrum antimicrobials, a laxative diet (mineral oil, mashes of complete pelleted feeds or alfalfa pellets, fresh grass), and NSAIDs to facilitate defecation. Certain grade III tears can be managed similarly; however, they require daily manual evacuation for up to 3 weeks.

For grade III tears, peritonitis is a sizable risk, repeated epidurals are required, and the time and financial commitments are substantial. For the best outcome, grade III and IV tears should be referred to a surgical facility. However, it is essential to prevent fecal contamination of the abdomen during transport, so rectal packing is highly recommended, as follows:

1. The horse is sedated and an epidural performed.

2. A tampon composed of a 7.5-cm stockinette coated with water-based lubricant and filled with moist, iodine-soaked cotton is inserted until it is at least 10 cm beyond (cranial to) the tear. To avoid enlarging the tear, the stockinette should be inserted before being completely filled.

3. The anus is then temporarily occluded with a purse-string suture or towel clamp.

4. Systemic, broad-spectrum antimicrobials, NSAIDs, and appropriate tetanus prophylaxis are administered.

At the referral facility, the tear should be reassessed and an abdominocentesis performed to check for peritonitis. After assessment, several treatment options are available. Grade II tears without fecal contamination that are at risk of forming a diverticulum can be treated with primary repair via a rectal approach to suture using one hand. The horse should be monitored carefully for development of a perirectal abscess, which requires surgical drainage.

For retroperitoneal tears with fecal contamination, the tear can be packed with iodine-soaked gauze and the cavity cleaned out daily. In mares, the cavity can be drained into the vagina and the tear closed primarily. A laxative diet and analgesics are provided to decrease the pain of defecation. The most serious complication of retroperitoneal tears is development of an abscess that migrates forward into the abdominal cavity. Ensuring drainage into the rectum or vagina can help prevent such abscesses.

Grade III or IV tears in a caudal location can be treated with primary repair by hand-suturing through a rectal approach; however, a successful outcome requires minimal to no contamination of the abdomen. Successful repair of a grade IV tear using a linear stapling device has been reported (1).

Alternatively, grade III and IV tears can be treated via a ventral midline approach to improve access. A celiotomy has the advantage of abdominal lavage and concurrent large-colon evacuation, thus decreasing the pressure of ingesta on the suture line.

Grade III and IV tears can also be treated by insertion of a rectal liner via ventral midline celiotomy. Rectal liners are made of a plastic ring glued to a rectal sleeve. The liner is introduced rectally by a nonsterile assistant and sutured to the small colon using an external circumferential suture pattern that allows the ring to slough in approximately 10 days, resulting in a small-colon anastomosis. The liner diverts the normal fecal passage until the tear has healed.

For some grade III and IV tears, a loop colostomy can be performed. The colostomy is a first step; after the tear has healed, colonic continuity is reestablished in a second surgical procedure. In all fecal diversion procedures, an attempt is usually made to close or approximate the tear. Laparoscopic suturing of rectal tears has also been described (2).

Postcastration evisceration is a risk with all open castrations; the risk is higher in draft horses, Tennessee Walking horses, American Saddlebreds, and Standardbreds, as well as in adult stallions, because of their larger inguinal rings. Evisceration typically occurs within 4 hours after castration, but it is a risk for up to 6 days after surgery.

• Physical examination

• Transrectal palpation

The first indication of evisceration of omentum or small intestine is a structure hanging out of the surgical incision. The owner should be instructed to keep the horse quiet and support the eviscerated structure(s) with a towel to avoid further stretching, tissue damage, and contamination. Examination quickly reveals the structure involved, and treatment can then be initiated.

• Emasculation of eviscerated omentum

• Reduction of herniated bowel

• Referral for surgical reduction or resection

For omental evisceration (see omental evisceration image), the horse is restrained and rectal palpation performed to confirm that only the omentum is involved. Omental prolapse can be managed by sedation and emasculation of the omentum as far proximally as possible.

Omental evisceration, horse

Image

Courtesy of Dr. Amelia Munsterman.

Alternatively, the horse is placed in dorsal recumbency under short-term general anesthesia, and the omentum and scrotum are cleaned and sterilely prepared. The omentum is emasculated as proximally as possible, and the scrotum is packed with gauze and closed temporarily. Systemic antimicrobials and anti-inflammatory medications are administered, and the packing is removed in 2 days. Barring complications, antimicrobials are discontinued on day 3.

If the small intestine is eviscerated, a short-term general anesthetic is administered. The intestine is copiously lavaged and examined for damage. Avulsion of the mesenteric vessels or intestinal compromise requires resection. The scrotum should be sutured closed over the eviscerated bowel and the horse referred to a surgical facility for ventral midline celiotomy.

If the intestine appears healthy and without severe contamination, it can be replaced in the abdomen at the time of the initial examination. This procedure often requires dilation of the internal inguinal ring. Care should be taken to replace the intestine in the peritoneal cavity through the inguinal canal and not through a separate, iatrogenic opening. If the herniation cannot be reduced confidently, the scrotum should be sutured closed over the herniated intestine and the case referred.

If the herniation can be reduced, the inguinal canal and scrotum are packed with sterile gauze, with care taken to prevent the introduction of gauze into the abdomen, and the scrotum is sutured closed temporarily. A short segment of gauze is left exposed. Alternatively, the external inguinal ring and vaginal tunic can be sutured closed primarily instead of being packed; however, this procedure must be performed under aseptic conditions.

Systemic, broad-spectrum antimicrobials and anti-inflammatory medications are administered, and the horse is monitored closely for development of colic or ileus, which can indicate intestinal devitalization. With intestinal devitalization, the horse must be referred for abdominal exploratory surgery.

If the horse progresses well, packing can be removed in 48 hours, and antimicrobials can be discontinued 24 hours after removal. A rectal examination should be performed before the packing is removed, to ensure that herniation has not recurred and the intestine has not adhered to packing material.