Choke and Esophageal Disorders
Bradford P. Smith • Charles L. Guard
Definition and Etiology
Choke is the term used for esophageal obstruction. In ruminants it is most common in cattle because of their eating habits, but it has even been reported in a goat that ate thread with a needle attached.1 If the obstruction is complete, the condition is rapidly fatal (except in neonates) because of the inability to eliminate the gases of fermentation produced in the rumino- reticulum.
Partial obstruction produces dysphagia or anorexia. Obstruction may be caused by the ingestion of foreign objects or large chunks of solid feedstuffs such as apples, potatoes, beet tops, corn cobs, or even a mango.2 Dry grain, particularly in pellet form, may be consumed so rapidly that sufficient saliva is not produced to lubricate the passage of the feed boluses. This is more common in sheep than in other ruminants; with grain, spontaneous resolution usually occurs within minutes to hours. Obstruction also may be the result of space-occupying lesions in or near the esophagus. Choke must be differentiated from diseases that cause dysphagia by means of pharyngeal lesions and resultant neuromuscular dysfunction. Congenital or acquired lesions of the esophagus, such as aortic arch anomalies and diverticula, may cause signs similar to those of esophageal obstruction.Clinical Signs and Differential Diagnosis
The earliest signs of complete esophageal obstruction from intraluminal objects are anxiety and ptyalorrhea (i.e., saliva dripping from the mouth because of an inability to swallow). The animal may violently swing the head from side to side and make repeated attempts to swallow. Staggering (which must be differentiated from ataxia caused by neurologic diseases) may be observed. Bloat develops soon after at a rate that depends on the nature of the ruminoreticular contents.
Intraluminal objects commonly causes obstruction in the cranial part of the cervical portion of the esophagus, at the thoracic inlet, or at the base of the heart. In a 2-week-old calf with a cloth foreign body obstructing the distal esophagus at the cardia, regurgitation after drinking milk was observed.3 External palpation may localize the site of obstruction in the cervical portion of the esophagus. With more slowly developing and incomplete obstruction, anorexia and dysphagia may be observed. Bloat may occur repeatedly and resolve spontaneously or after passage of a stomach tube. The underlying cause may result in signs severe enough to mask the esophageal problem. Cellulitis along the cervical portion of the esophagus may result in a reluctance to lower the head or bend the neck laterally. Possible causes of cervical cellulitis include perivascular injection of irritating substances, abscesses, and reaction to Hypoderma Iineatum larvae.
Esophageal stricture may follow a previous episode of esophageal obstruction or inflammation in adjacent tissues. If no site of obstruction is externally evident, careful attempts to pass a stomach tube usually reveal the site of the problem. Radiography with barium contrast material may help identify the site of strictures, perforations, and diverticula. Endoscopy of the esophagus may also aid in identifying the specific nature of functional or structural abnormalities. Megaesophagus has been observed after pharyngeal trauma, as a congenital disorder, and with hiatal hernia. An esophageal stricture or a diverticulum may cause reflux of boluses of feed mixed with saliva or regurgitation of liquid ruminal contents. Failure to gain weight or progressive weight loss accompanies the failure to swallow feed successfully. Signs may be seen only when forage is consumed, whereas water and grain are swallowed normally.
Systemic diseases may lead to esophageal dysfunction. Rabies must always be considered when dysphagia is present, and appropriate precautions must be taken.
Botulism also leads to esophageal transport failure, although dysphagia and a weak tongue are more prominent in the affected animals that do not eat. Tetanus may be similar in appearance to esophageal obstruction because of the presence of bloat, dysphagia, and drooling. Several poisonous plants, including sneezeweed, larkspur, and milkweed, may cause excessive salivation, drooling, and bloat. Consumption of red clover infected with the fungus R. Ieguminicola, which produces the toxin slaframine, results in copious salivation. Pharyngeal trauma and subsequent cellulitis lead to dysphagia and drooling, but severe bloat does not occur unless the swelling is sufficient to occlude the esophagus. However, mild bloat frequently accompanies pharyngeal trauma caused by associated vagal nerve inflammation and dysfunction.Clinical Pathology
Common features of long-standing choke are dehydration and metabolic acidosis resulting from continued loss of sodium bicarbonate and sodium phosphate in saliva. As sodium depletion develops, the composition of saliva shifts to include more potassium under the influence of aldosterone. Inflammatory diseases lead to predictable changes in the hemogram.
Necropsy Findings
Animals that die of acute esophageal obstruction are bloated and may have saliva and feedstuffs in the upper airway. Postmortem examination of animals with protracted esophageal dysfunction may reveal focal dilations or stenoses of the esophagus. Esophageal perforation may have occurred because of pressure around an intraluminal foreign body or necrosis caused by extension of an adjacent septic process.
Treatment and Prognosis
In cases of complete esophageal obstruction, relieving bloat is the first concern. Passage of a stomach tube may be attempted if the animal is not in respiratory distress. Trocharization of the rumen or installation of a temporary fistula may be required. Until the esophagus has been cleared, it is important to keep the muzzle level or pointed down to reduce the risk of aspiration of saliva.
Sedative drugs such as acepromazine or xylazine may be useful for calming an animal and enabling careful examination. Suitable precautions should be taken if rabies is remotely possible. The history and an examination of the environment should enable the clinician to anticipate the nature of the obstructing object. Palpation of the neck along the left jugular furrow may reveal the site of obstruction in lean or thin-necked animals. A manual oral examination should precede probing attempts with a stomach tube. Gentle pressure on the stomach tube as it passes down the esophagus should allow localization of the obstruction. A small hand can reach into the cranial part of the esophagus and may retrieve some solid objects. If the object is solid (e.g., a potato), it may be possible to massage it into the pharynx by pressing in the jugular furrow on both sides of the neck. Specialized equipment, such as a probang, is available with a corkscrew-like or pincer-like end that can be used to grasp or engage a foreign body and expedite its retrieval. If a mass of grain is obstructing the esophagus, external massage, probing with the stomach tube, or pumping fluid against the mass through the tube may break it up.If the choke is intrathoracic and probing with a stomach tube does not relieve the problem, several courses of action are possible. A small ruminal fistula can be inserted to prevent bloat, and the animal can simply be placed in a pen without bedding, feed, or water. Many masses consisting of grain or hay spontaneously pass within 24 hours, whereas solid objects rarely pass spontaneously. If the obstruction does not resolve in 24 hours, the animal can be heavily sedated, a cuffed endotracheal tube can be passed to prevent aspiration, and vigorous lavage with water through a stomach tube can be attempted. The head should be held lower than the body to minimize the risk of aspiration. If the obstruction still cannot be relieved or it is believed that the obstruction is a solid object, a rumenotomy can be performed.
Access to the esophagus through the cardia should allow snaring of the object with a loop of stiff wire or breakup of a mass of grain.The long-term prognosis after choke is good unless the esophageal mucosa has been damaged. Stricture formation may follow cellulitis or pressure necrosis at the site of the obstruction. Aftercare for the choked animal consists of a soft diet and antiinflammatory drugs to minimize tissue swelling. Well-soaked alfalfa cubes made into a mush may pass partly obstructed areas. Hay and grain should be moistened before feeding, and grain should be offered only in small amounts at each feeding. Broad-spectrum antibiotics should be given if mucosal damage is suspected. Maintenance of an indwelling nasogastric tube for feeding for up to 10 days after severe esophageal trauma may be helpful in preventing strictures during healing. Thick gruels made from soaked alfalfa cubes or pellets can be pumped into the rumen by a bilge pump designed for boats, or the animal can be fed and watered through a ruminal fistula. Surgical exploration may be required to determine the cause of esophageal obstruction from spaceoccupying lesions or strictures. Abscesses may be drained, and granulomatous lesions resected. Esophageal diverticula, aortic arch anomalies, and intrathoracic surgical problems are not easily treated.