Also see Diseases of the Esophagus in Large Animals: Esophageal Obstruction (Choke) in Large Animals.
Intraluminal esophageal obstruction is common in horses and is generally caused by impaction of feed material. The most frequent sites of impaction are the proximal esophagus and just cranial to the thoracic inlet. Predisposing factors include bolting of food, improper chewing of food (poor dentition), recent sedation, poor feed quality, and dehydration.
Clinical signs of choke include nasal discharge containing saliva and feed material, hypersalivation, coughing, and frequent attempts to swallow. Esophageal obstruction is identified by palpation of the neck, passage of a nasogastric tube, or endoscopy. In refractory cases, radiography and contrast radiography may be used, particularly if a foreign body, stricture, or diverticulum is suspected.
Once the presence of an obstruction has been confirmed, the horse should be muzzled to prevent packing of feed at the obstruction site. Many obstructions resolve with sedation and consequent relaxation of the esophageal musculature. An α2 agonist such as xylazine or detomidine provides good relaxation. Oxytocin (0.11 mg/kg, IV) has been demonstrated to provide good esophageal relaxation and has been used successfully to resolve esophageal obstructions. Once an esophageal relaxant has been given, the obstruction often resolves within ~1 hr. If the horse is dehydrated, IV fluids may also help resolve the obstruction.
If the obstruction has not resolved after ~1 hr, a nasogastric tube is passed, and after adequate sedation (to lower the head), gentle lavage with water or 0.9% saline is used to flush the esophagus. Mineral oil should never be used due to the risks associated with aspiration. An esophageal lavage tube—essentially a nasogastric tube with a cuff—is useful to help resolve the obstruction. Alternatively, an endotracheal tube can be passed through the nasal passages and into the esophagus, and a smaller nasogastric tube is used for lavage. These procedures can be repeated intermittently and are facilitated by general anesthesia. However, if unsuccessful after a few hours, further tests may be required to exclude the presence of a foreign body.
After the obstruction has been relieved, endoscopy can be used to assess the esophageal mucosa. Circumferential ulceration can lead to stricture formation with recurrence of the obstruction. Horses that have choked are at risk for recurrence in the 2–4 wk after the initial event even without visible esophageal damage. Feeding a slurried, pelleted diet or grass can prevent recurrence. When the esophagus has been damaged, narrowing maximizes at 30 days. Before attempts are made to resolve a potential stricture, the horse should be managed medically with dietary modification for 60 days. Broad-spectrum antibiotics are administered to prevent or treat aspiration pneumonia, along with anti-inflammatory drugs. Sucralfate has been advocated to facilitate healing of ulcers.
Also see Diseases of the Rectum and Anus: Rectal Tears.
Rectal tears are serious injuries in horses. Prevention is key, but if a rectal tear should occur, appropriate and timely referral can result in a successful outcome. Rectal tears are classified into 4 grades based on the number of layers involved and their craniocaudal location. Grade I involves the mucosa and submucosa only; grade II involves the muscularis, with a mucosal-submucosal hernia; and grade III involves the mucosa, submucosa, and muscularis, leaving the serosal layer intact. In the case of a grade III tear located in the retroperitoneal area, there is no serosa, so the tear is complete and extends perirectally. Grade IIIa tears leave the visceral peritoneum intact; grade IIIb tears are located in the mesorectum. Grade IV involves the mucosa, submucosa, muscularis, and serosa. There is potential for fecal contamination of the abdomen. Most tears resulting from rectal palpation are located dorsally within the peritoneal cavity and extend into the mesocolon.
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, the severity should be immediately assessed and measures taken to initiate treatment or referral.
The horse should be sedated during assessment and an epidural performed if there is any straining. Propantheline bromide can be given to decrease peristalsis. A speculum should not be used, as it can worsen the tear. Digital palpation (preferably bare handed) is carefully performed. A thin flap of tissue indicates a tear through only the mucosa. If a large cavity with a thin membrane is noted, then a grade III tear is present. If intestine can be palpated, the tear is a grade IV.
Grade I and II tears can be managed medically with antibiotics and a laxative diet (oil, grass) and analgesics (flunixin meglumine) to facilitate defecation. Grade III and IV tears should be referred to a surgical facility. However, it is essential to prevent fecal contamination during transportation. Rectal packing is highly recommended to achieve this goal. The horse is sedated, and an epidural is performed, using a combination of xylazine and mepivacaine. A tampon composed of a 6.5-cm stockinet filled with cotton is inserted until located at least 10 cm cranial to the tear, and the anus is occluded with a purse-string suture or towel clamp. The stockinet should be inserted before filling it completely, to avoid further enlargement of the tear. The horse should be given systemic broad-spectrum antibiotics, flunixin meglumine, and appropriate tetanus prophylaxis. Prevention of fecal contamination of grade III and IV tears during referral can determine whether the outcome will be successful.
At the referral facility, the tear is reassessed to check for additional damage during transportation. An abdominocentesis is performed to check for peritonitis. Following assessment, several treatment options are available. For grade II tears with no fecal contamination, primary repair by a rectal approach can be attempted using 1-handed ties. The horse should be monitored carefully for development of a perirectal abscess. For grade III retroperitoneal tears with fecal contamination, the tear can be packed with iodine-soaked gauze and the cavity cleaned out daily. In mares, the cavity may be drained into the vagina and the tear closed primarily. A laxative diet is provided, with additional laxatives such as mineral oil. Defecation is often painful for these horses, so analgesics are provided as needed. The most serious complication of retroperitoneal tears is development of an abscess that migrates forward into the abdominal cavity (point of least resistance). This is prevented by ensuring appropriate drainage into the rectum or vagina. For grade III and IV peritoneal tears in a caudal location, primary repair through a rectal approach can be attempted. A successful primary repair of a grade IV tear using a linear stapling device has been reported. This approach requires that the abdomen has not been contaminated or that the contamination is minimal. Alternatively, these tears can be treated through a ventral midline approach, followed by an antimesenteric incision in the caudal small colon and repair through the lumen. The abdominal approach is very caudal and involves separation of the udder in mares or a preputial reflection in males. This approach has the advantage of allowing the large colon to empty, thus reducing fecal load.
Grade III and IV tears can also be treated by insertion of a rectal liner. Rectal liners are made from a plastic ring glued to a rectal sleeve. The liner is sutured to the small colon mucosa, via an enterotomy, and the sleeve protects the tear during healing. The ring is sloughed in ~10 days with normal mucosal turnover. In other cases, a loop colostomy can be performed to maintain patency of the distal segment. The colostomy is performed as the first step; after healing of the tear, colonic continuity is reestablished. In all fecal diversion procedures, an attempt should be made to also close or approximate the tear. If large, it may heal with a fistula.
Postcastration evisceration is always a risk following open castrations, but the risk is increased in Standardbreds and Belgians (due to their larger inguinal rings) or after castration of an adult stallion.
Evisceration of omentum or small intestine is first identified by a structure hanging out of the surgical incision. It is important to instruct the owner to keep the horse quiet and to support the eviscerated structure with a towel to avoid further stretching or damage. Examination quickly reveals what structure(s) is involved so that treatment can be initiated.
In cases of omental evisceration, a rectal palpation should be performed to ensure that only omentum is involved. A short-term general anesthetic is given. The omentum and scrotum are cleaned and prepped, and the omental segment is emasculated. The scrotum is packed with gauze and closed, and the horse is given systemic antibiotics. The packing can be removed after 2 days, with antibiotics continued for 24 hr after removal of the pack.
If small intestine is eviscerated, a short-term general anesthetic is given. The intestine is copiously lavaged and examined for damage. Avulsion of mesenteric vessels or strangulation require resection, so the scrotum should be sutured closed and the horse referred to a surgical facility. If the intestine appears healthy, it is replaced in the abdomen, which often requires cutting the internal inguinal ring. Care should be taken to replace the intestine within 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 packed and the case referred. If the herniation can be reduced, the inguinal canal and scrotum are packed with sterile gauze, and the scrotum is sutured closed (leaving a short segment of gauze exposed). Systemic broad-spectrum antibiotics are administered, and the horse is monitored closely for development of colic or ileus, which indicate intestinal devitalization. Should that occur, the horse must be referred for an abdominal exploratory surgery. If the horse progresses well, the packing can be removed in 48 hr, and the antibiotics discontinued 24 hr after removal of the packing.
Last full review/revision March 2012 by Pamela Anne Wilkins, DVM, MS, PhD, DACVIM-LA, DACVECC