Idiopathic Megaesophagus Clinical Update
Internal Medicine Clinical Update: Idiopathic Megaesophagus
Michael Goldstein, DVM, Diplomate ACVIM
Megaesophagus is a condition characterized by decreased or absent esophageal motility that results in a diffuse dilation of the esophagus. This condition occurs as either a congenital disorder or more commonly as an acquired disorder in adult dogs. Aquired megaesophagus can be secondary to a variety of diseases (see bottom of hand out for rule out chart) or most commonly as a primary disorder which the cause is unknown (idiopathic megaesophagus), which is the focus of this clinical update.
Idiopathic megaesophagus can occur in any breed or sex and typically presented between 5 and 12 years. Dogs with idiopathic megaesophagus usually present for regurgitation but other clinical signs include ptylism, halitosis and vomiting. Dogs with megaesophagus are predisposed to aspiration pneumonia and can present with dyspnea, cough, and nasal discharge. Weight loss is often present.
In idiopathic megaesophagus the physical examination is typically normal but weight loss will likely be detected. Dyspnea, cough, nasal discharge, and auscultable moist rales or crackles may be present in dogs with aspiration pneumonia. Routine diagnostics: complete blood count (CBC), chemistry profile, urinalysis, and fecal examination results are usually within normal limits.
Idiopathic megaesophagus is made only after secondary causes have been eliminated. An underlying cause is found in only 15% to 25% of adult dogs. Most cases of generalized megaesophagus are evident on survey radiography. Contrast esophography can be used to distinguish megaesophagus from focal motility disorders. Due to the risk of aspiration, contrast imaging studies should be performed only when necessary. Megaesophagus can be a diagnostic challenge as it is difficult to distinguish between idiopathic megaesophagus and secondary megaesophagus. Diagnostic tests that for secondary megaesophagus should be performed based on the clinical presentation, physical examination and radiology findings.
Treatment for idiopathic megaesophagus is symptomatic in nature, as no treatment has proven to reverse the dilation of the esophagus. Specialized feeding practices are the main stay of therapy. It is recommend that feeding be from an elevated position where the upper body and forelimbs are elevated at least 45 ̊ relative to the hind limbs. The dog should remain in this position for 5 to 10 minutes after eating. There is no consensus on the optimal food to be fed or consistency. Gruels are often fed in the hope that they will “slide” down the esophagus easier; however, some pets tolerate dry food or canned foods in “meat-balls” better than gruels. My recommendation is to offer a low-fat, high-protein diets as they are documented to physiologically increase lower esophageal tone and decrease gastric emptying time. Feeding multiple small meals a day meal help minimize accumulation in the esophagus. Daily caloric intake should be calculated for dogs based on their ideal weight and patients should be weighed every 2 weeks to document any signs of failure to gain weight. Owners should be counseled at the time of diagnosis about the potential need long term for endoscopically placed gastrotomy tubes. These tubes are easily placed and provide good quality of life for many dogs with megaesophagus. Idiopathic megaesophagus is irreversible, and improvement of the patient’s condition is solely based on its ability to tolerate supportive feeding practices. Weight gain may not occur for several months.
In cases of idiopathic megaesophagus, weight gain, tolerance of oral feeding, and avoidance of aspiration pneumonia are favorable short-term signs. Recurrent bouts of aspiration pneumonia typically influence owners to choose euthanasia. Therefore close monitoring and constant contact with the owner is imperative for successful management.