Recognizing and treating esophageal disorders in dogs and cats

2004-05-01
Michael D. Willard, DVM, MS, DACVIM

Although esophageal disorders are less common than gastrointestinal diseases, they are not as rare as some practitioners think.

Although esophageal disorders are less common than gastrointestinal diseases, they are not as rare as some practitioners think. Unfortunately, esophageal disorders may often be overlooked since regurgitation, a sign of esophageal disease, closely mimics vomiting, which is more common and is associated with gastrointestinal disease. This article describes how to distinguish regurgitation from vomiting and how to diagnose and treat several common esophageal disorders.

DIFFERENTIATING BETWEEN REGURGITATION AND VOMITING

Vomiting animals usually have prodromal signs (e.g. salivation, licking of lips, pacing) followed by vigorous abdominal contractions. Bile may be seen in the vomitus. But keep in mind that there is a wide range of presenting signs, and some animals that appear to be vomiting may be regurgitating and vice versa.

A common assumption is that regurgitation occurs soon after eating. While this is true in some instances, many dogs will regurgitate hours, or even days, after eating. Conversely, dogs may vomit within minutes of eating.

In addition, observing partially digested material does not necessarily imply vomiting has occurred. Food that has sat in a dilated esophagus with saliva and water for a day or two may look partially digested to many owners.

Moreover, rather than asking a client if bile was present, instead ask if there was any obvious color to the ejected material, because the client may not be familiar with the term bile. If a patient throws up in your clinic, quickly determine the pH of the material with a urinary dipstick. This test will also determine if bilirubin is present. A pH of 5 or less indicates the presence of gastric acid (and hence, vomiting). A positive reaction for bilirubin confirms the presence of duodenal contents. In both instances, the patient is almost always vomiting. Finding a higher pH and a lack of bilirubin strongly supports regurgitation.

If, after obtaining a history and conducting a physical examination, you still cannot determine whether vomiting or regurgitation is occurring, then first look for esophageal disease by obtaining plain thoracic radiographs. If more detailed information is needed, you may perform contrast radiography (or better yet, fluoroscopy) or endoscopy. If plain and contrast radiographic findings of the thorax and esophagus are normal, then vomiting is most likely.

Cases of suspected vomiting due to gastrointestinal diseases primarily require investigating the abdomen. Performing a complete blood count and serum chemistry profile is recommended initially, as is performing abdominal imaging (e.g. radiography, ultrasonography). A final diagnosis may require endoscopy or surgery.

ESOPHAGEAL DISORDERS

Once you firmly establish that a patient is regurgitating, you must pinpoint the particular esophageal disorder. Esophageal diseases can be congenital or acquired. They may be due to weakness (e.g. myasthenia gravis), an obstruction (e.g. foreign body), or reflux (e.g. esophagitis). Although clinical signs of congenital esophageal disease typically appear when patients are young, the disease may not be diagnosed in some patients until they are several years old.

Esophageal weakness

Distinguishing esophageal weakness from esophageal obstruction is usually best done with radiography. Plain radiographs may be sufficient, but contrast radiography with oral barium administration is much more definitive and helps prevent diagnostic errors. Always obtain plain radiographs before contrast radiographs because, in many cases, plain radiographs are definitive or show that endoscopy is the best next step instead of contrast radiography (e.g. in cases of an esophageal foreign body).

Congenital esophageal weakness and congenital obstruction (e.g. vascular ring anomaly) will not be discussed here in detail because they are reasonably straightforward to diagnose. Keep in mind that vascular ring anomalies may be first diagnosed in older pets1 (i.e. more than 3 years old) or only after a foreign object obstructs the narrowed esophageal lumen. It can be easy to confuse segmental esophageal weakness proximal to the heart with a vascular ring anomaly causing obstruction. Sometimes this mistake is not recognized until the time of surgery. It is also worth noting that while surgery is indicated for vascular ring anomalies and the condition of most patients improves substantially with surgery,2 occasionally patients do not benefit from surgery.

Acquired esophageal weakness is also well-understood and has been discussed in detail elsewhere,3 but I want to emphasize two points. First, always look for a cause (e.g. localized myasthenia gravis, hypoadrenocorticism) rather than simply initiating supportive or symptomatic dietary modification. Treating the underlying cause of a megaesophagus results in a much better prognosis than simply altering the feeding practices and hoping that aspiration does not result. Second, aspiration pneumonia is the main cause of morbidity and mortality in patients with esophageal disease, especially in those with esophageal weakness. Aspiration may occur weeks or months before regurgitation is first noticed. Your index of suspicion for esophageal weakness should be high in patients with recurrent pneumonia or chronic cough even without a history of regurgitation, vomiting, or dysphagia. In these cases, esophageal function should be assessed by fluoroscopic barium contrast esophagograms so proper treatment of underlying esophageal weakness can be attempted. Remember, canine pneumonias are generally not spread from dog to dog (unless caused by Bordetella bronchiseptica), so always look for the cause, most commonly either fungal infection or aspiration.

Esophageal foreign bodies

Esophageal foreign bodies are not common but are seen frequently enough that practitioners must be adept at diagnosing them, otherwise the consequences can be catastrophic (e.g. pyothorax). The key to suspecting esophageal foreign bodies is to recognize that the acute vomiting reported by a client is actually acute regurgitation. In such cases, immediately obtain thoracic radiographs. Most esophageal foreign bodies do not show up as obvious esophageal lesions on plain radiographs. Instead, they often appear as ill-defined, soft tissue opacities that look as if they could be in the pulmonary parenchyma.

Whenever a suspected pulmonary mass is detected radiographically, consider whether it could be an esophageal mass. If there is any possibility the mass is esophageal, your next step should be to perform contrast radiography or endoscopy (which is usually preferred). In general, endoscopic manipulation is the best way to resolve most cases of esophageal foreign objects.4 Surgical removal is necessary when the object cannot be removed endoscopically. If endoscopy is anticipated, avoid contrast esophagograms, because barium tends to obscure the visual field and makes endoscopic removal more difficult. Contrast films are rarely needed to detect esophageal perforation. Discovering a pneumothorax or pleural fluid on plain radiographs should make you strongly suspect an esophageal perforation. Obtain pleural fluid for cytologic examination to diagnose sepsis.

Rigid endoscopy is often more effective than flexible endoscopy for removing esophageal foreign bodies. Rigid endoscopes allow the use of rigid forceps, which permit a much stronger grip on the object and more delicate and precise manipulation of the object to free it from any ulcers or craters it has created. Carefully placing the edge of the rigid endoscope against a lodged bone may allow the rigid forceps to break off pieces of the bone or even to break it in two, without further injuring the esophagus. This maneuver is especially helpful when the bone has eroded deep ulcers into the esophagus and cannot be removed otherwise. A foreign body can be partially drawn into the rigid endoscope, facilitating its removal from the esophagus. This is especially valuable if you are attempting to remove sharp-edged objects or trying to pull objects through the cricopharyngeal area. Likewise, most fishhooks, even treble hooks, can be removed endoscopically.5 Again, rigid endoscopic equipment is preferred and can usually be used successfully, even if the hook and barb have penetrated the esophageal mucosa. The limiting factors in removing such hooks are the size of the barb (i.e. large barbs will not tear out of the mucosa) and whether the hook and barb have penetrated the esophagus and could lacerate the great vessels of the heart if they are pulled back into the esophagus. In these cases, surgical removal is warranted.

After removing a foreign object, immediately reexamine the esophagus endoscopically to assess the degree of esophagitis. Also obtain a thoracic radiograph to check for evidence of pneumothorax, which would indicate perforation has occurred. While perforation generally requires referral for surgery, a small perforation might heal spontaneously if pleural contamination is avoided. If a minor perforation has occurred, placing a gastrostomy tube endoscopically may allow the perforation to heal. (The gastrostomy tube prevents food, water, and medications from traversing the esophagus.) Depending on the amount of esophageal damage, it may be advisable to treat the patient for esophagitis (i.e. placing a gastrostomy tube and providing aggressive antacid therapy and gastric prokinetic therapy).

Esophagitis

Esophagitis is probably more common than practitioners think. Diagnosing it is problematic, because a) the clinical signs vary tremendously, depending on its severity; b) it can be hard to definitively diagnose radiographically; c) endoscopy is the best method of diagnosis, but not all practitioners have access to endoscopy; and d) it may not always be on practitioners' lists of differential diagnoses.6

Common causes of esophagitis include ingestion of caustic substances (including prescribed medications), excessive vomiting of acidic gastric contents, acid reflux, and trauma from foreign objects (previously discussed).

Common caustic substances responsible for esophagitis include oral administration of tetracycline and doxycycline monohydrate. In particular, failure to wash down a pill or capsule with water is commonly associated with retention of the pill in the esophagus for minutes to hours after administration. This retention is particularly common in cats.7 Esophagitis may result when cats lick caustic substances, such as disinfectants and cleaning agents, from their fur. In such cases, glossitis and stomatitis may alert you to possible esophageal inflammation.

Perhaps the most common cause of esophagitis is repetitive vomiting (e.g. in cases of parvoviral enteritis in dogs or gastric outflow obstruction in cats). Puppies with parvoviral enteritis may appear to have recovered from the disease, but continue to throw up. On closer examination, the vomiting is actually regurgitation. Diagnosing megaesophagus in cats should lead you to question whether repeated bouts of vomiting have resulted in the megaesophagus secondary to esophagitis.

Gastroesophageal reflux may be caused by hiatal hernias, especially in Shar-Peis. Radiography is a specific but insensitive means of detecting hiatal hernia. Endoscopic examination is more sensitive, but experience is required to recognize the lesion.

Perhaps the most worrisome cause of esophagitis secondary to gastroesophageal reflux is anesthesia. Some patients anesthetized for even the most routine procedures, such as spaying or neutering, will unpredictably experience severe gastroesophageal reflux during anesthesia.8,9 The problem is clinically silent when it occurs, but these patients typically have a poor appetite or anorexia immediately after surgery and in the days after surgery. This subtle sign is a first ripple in what can figuratively become a tidal wave. When esophageal inflammation persists, severe stricture can result.

Radiographic findings caused by esophagitis are usually subtle, although some cats will develop megaesophagus. Even a barium esophagogram may show relatively modest changes that most practitioners will miss (e.g. minor retention of barium on the mucosal surface or modest retention of barium in the esophagus). Esophagitis is best diagnosed endoscopically. It often appears as obvious inflammation, as evidenced by hyperemia and bleeding. If the esophageal mucosa bleeds during routine endoscopy, esophagitis must be highly suspected. In rare cases, there may be a pseudomembrane on the surface of the esophagus, but this is usually obvious. Esophageal biopsy may reveal some cases of esophagitis missed by gross examination, but it is difficult to obtain a biopsy sample from the esophagus (except when there is acute inflammation or a tumor), so endoscopic esophageal biopsy samples are seldom obtained. For the above reasons, the incidence of esophagitis is unknown.

The lesions of esophagitis can be mild, moderate, or severe. Severe esophagitis can affect esophageal motility to the point that gastroesophageal reflux results. The condition tends to worsen because of the establishment of a positive feedback loop (i.e. the esophagitis has caused laxity of the lower esophageal sphincter, which has allowed gastroesophageal reflux, which worsens the esophagitis, which ultimately results in more reflux). The crux of the problem is that while the stomach is accustomed to acid, a damaged esophagus is not. Amounts of acid that would be negligible for the stomach may perpetuate and worsen esophageal ulceration or erosion. Because of this cycle, it is important to shut down gastric acid secretion as completely as possible (i.e. chemical clearance). The proton-pump inhibitors (e.g. omeprazole) more effectively suppress acid secretion than do the H2 receptor antagonists such as famotidine. A disadvantage of omeprazole, however, is that it is only available in an oral preparation.10

It is also important to treat esophagitis by administering promotility agents, which cause volume clearance (i.e. forcing gastric secretions such as pepsin into the duodenum instead of allowing them to reflux into the esophagus). While metoclopramide is useful, cisapride seems much more effective. Although cisapride has been taken off the human medical market, it is available through veterinary compounding pharmacies. Once again, a principal disadvantage is that cisapride must be given orally. However, if a gastrostomy tube has been placed, then oral medications may be administered through the tube, bypassing the esophagus.

Gastroesophageal reflux may occur in the absence of obvious causes such as chronic vomiting or a hiatal hernia, but the incidence of such causes is unknown. Hiatal hernias can result in regurgitation or esophagitis and can be particularly difficult to diagnose. Many times, fluoroscopic examination is required. However, many normal dogs will have an occasional reflux during a barium esophagogram. Making a confident diagnosis of gastroesophageal reflux requires observing multiple episodes of reflux during a barium esophagogram.

Benign esophageal stricture

A common result of poor or no treatment of esophagitis is esophageal cicatrix causing a stricture.6 The principal points to remember about cicatrices are a) they are usually partial, such that administration of liquid barium may or may not reveal them, even if fluoroscopy is used; b) it is far easier to prevent a benign stricture than to resolve a serious one; and c) ballooning and bougienage are the preferred ways to treat strictures.11,12 Esophageal surgery should be avoided if at all possible.

Although ballooning has been touted as being superior to bougienage, experience in human medicine suggests that either can be effective, provided that the operator has been trained well. The goal is not necessarily to return the patient to a state of normalcy, but to make the pet functional, even if that means the diet must be softened. Some patients will only need to have their stricture dilated once or twice, while others will require dilation two or three times a week for up to 20 times. Ballooning should by performed only by those trained in the technique.

Various adjunct medical management schemes have been tried to make the procedure more effective sooner, including systemic and intralesional corticosteroids.13 At this time, there are no data showing that corticosteroid administration enhances success of esophageal dilation in dogs or cats. Some benefit may result from using electrocautery snares and knives to make a three- or four-quadrant set of cuts into dense strictures before dilation is attempted. The idea is that by making such cuts, dilation will result in a more even set of breaks in the cicatrix instead of one deep break that may then heal and form an even worse stricture. My experience is that more than 80% of patients will become functional, if the clinician is allowed to balloon as often as is needed.

SUMMARY

Esophageal disease is not as rare as practitioners might think. Esophageal foreign bodies, esophagitis, and benign esophageal stricture, in particular, may frequently be missed unless you have a high index of suspicion for these conditions.

Michael D. Willard, DVM, MS, DACVIM

Department of Veterinary Small Animal Medicine & Surgery

College of Veterinary Medicine

Texas A&M University

College Station, TX 77843-4474

REFERENCES

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