1. Define the Problem - Differentiating Regurgitation from Vomiting

The key feature of regurgitation is that it is a passive process with minimal abdominal effort that usually results in production of undigested food or water, often soon after ingestion. The premonitory signs, active abdominal contractions and bilious fluid that are usually present in vomiting animals are typically absent in patients with regurgitation. However, pain or inflammation in the esophagus can lead to stretching and arching of the neck, gagging, hard swallowing and hypersalivating, mimicking the signs associated with vomiting. One clue may be the severity of clinical signs: Animals with esophageal disease may regurgitate saliva as frequently as hourly and yet usually remain bright and systemically healthy. A vomiting animal is unlikely to sustain this frequency of vomiting without developing other systemic signs of disease. Table 1 summarizes specific questions that may be useful in obtaining an accurate clinical history from the animal's caregiver.

2. Consider the Differential Diagnoses

After correctly identifying the problem as regurgitation, the following differential diagnoses should be considered:

• Megaesophagus'- Megaesophagus is a syndrome characterized by decreased motility of the esophageal muscle resulting in generalized dilation of the esophagus. Megaesophagus can be classified as congenital or acquired. The acquired form has been reported to occur secondary to various underlying diseases including myasthenia gravis, hypoadrenocorticism, hypothyroidism, diffuse peripheral neuropathies and dysautonomia. However, the most commonly there is no identifiable underlying cause and these cases are classified as idiopathic. There has recently been increased interest in whether a subset of these patients might actually have lower esophageal sphincter dysfunction.
• Esophagitis'- Esophagitis may develop due to gastroesophageal reflux, chronic vomiting or the presence of caustic substances in the esophagus (importantly including medications such as doxycycline and clindamycin). Gastroesophageal reflux after prolonged anesthesia may occasionally result in particularly severe esophagitis and stricture formation.
• Esophageal stricture'- Esophageal stricture formation may be a complication of esophagitis. Affected patients may tolerate water but often regurgitate all solids immediately after eating. An inciting event - an anesthetic event, administration of a caustic medication or recent recovery of an esophageal foreign body - can usually identified.
• Esophageal foreign body'- Esophageal obstruction is most commonly seen from ingestion of soft treats and bones that are too large to pass through the esophageal lumen. Smaller dogs are at higher risk since the esophageal lumen is disproportionately small compared to the size of many common treats. Dogs with esophageal foreign bodies will present with gagging, retching and ptyalism. Food will usually be regurgitated immediately after ingestion - often forcefully.
• Esophageal neoplasia'- Esophageal neoplasia is uncommon in dogs and cats. Lesions at the lower esophageal sphincter may, however, mimic the clinical signs of megaesophagus
• Vascular ring anomaly'- Vascular ring anomalies are congenital malformations of the great vessels that subsequently encircle the esophagus causing obstruction. Clinical signs are typically first noticed after the animal is weaned onto solid food.
• Upper gastrointestinal obstruction'- Gastric outflow obstruction or severe upper small intestinal obstruction will lead to accumulation of fluid orad to the obstruction. This fluid may reflux into the esophagus and potentially lead to passive regurgitation of fluid. This may be more discolored or bilious than typical esophageal contents. Although not a primary esophageal disease, this may mimic esophageal disease and is an exception to the rule that regurgitation is associated with esophageal disease and that patients with gastric disease will vomit.

3. Investigate It

The following diagnostic tests are helpful in evaluating a patient with esophageal disease.

• Thoracic radiographs'- Thoracic radiographs are the most valuable diagnostic tool for evaluating esophageal disease and should be performed whenever regurgitation is a confirmed or potential problem. Radiographs should ideally be performed without sedation or anesthesia. In patients with megaesophagus, radiographs are expected to show generalized gas dilation or food/fluid dilation of the esophagus. However, it is possible to have clinically significant esophageal hypomotility without radiographically overt esophageal dilation. Thoracic radiographs are also the test of choice for the diagnosis of esophageal foreign bodies and may show evidence of neoplasia. They are also important to rule out secondary aspiration pneumonia.
• Contrast studies'- A barium study may provide evidence for esophageal hypomotility in the face of normal plain films. There is no indication for contrast studies where plain radiographs show overt esophageal dilation. Use of fluoroscopy will improve the sensitivity over static radiographs.
• Endoscopy'- Endoscopy is helpful to evaluate the esophageal mucosa and can help in the evaluation and treatment of obstructions, esophagitis, lower esophageal sphincter dysfunction or caudal esophageal masses. Esophagoscopy cannot provide any assessment of esophageal motility.
• Ultrasound'- Ultrasound may help rule out reflux secondary to rule out upper gastrointestinal tract obstruction but is generally unhelpful in the investigation of primary esophageal disease.
• Further investigations'- In the patient with megaesophagus, additional diagnostics are indicated to rule out potential underlying diseases.

4. Treat It

• Manage the underlying cause'- In patients with secondary, acquired megaesophagus, the primary treatment priority is to manage the underlying cause. Esophageal foreign bodies should be removed immediately - a longer indwelling time for an esophageal foreign body significantly increases the risk for esophagitis and subsequent stricture formation. Strictures can be managed with intermittent or indwelling balloons
• Treat esophagitis'- Esophagitis is treated supportively with acid blocking drugs (e.g., omeprazole 1 mg/kg PO BID). Sucralfate (0.25'1 g TID) can also be used to help protect ulcerated areas of the esophagus.
• Nutritional support'- In general, patients with esophageal disease that want to eat and can keep the food down should be fed small frequent meals by mouth. However, supplemental enteral nutrition or hydration may need to be provided if there is severe esophageal disease or frequent regurgitation. Gastrostomy tubes are generally preferred since the diseased esophagus needs to be bypassed.
• Promotility drugs'- Promotility drugs have no effect on the striated muscle of the esophagus. However, there is smooth muscle in the lower esophageal sphincter and cisapride may be helpful in some patients with gastroesophageal reflux. There are also some reports of the use of sildenafil or local botulinum toxin to reduce lower esophageal sphincter tone in some patients with megaesophagus.

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Peter S. Chapman, BVetMed, DECVIM-CA, DACVIM, MRCVS'
Veterinary Specialty and Emergency Center
Blue Pearl Pennsylvania
Levittown, PA, USA'