Sometimes megaesophagus is not visible at all on plain radiographs. If the animal has signs of a swallowing disorder, you'll
need an esophagram to make the diagnosis. When the megaesophagus is more severe or static, administering some liquid barium
and taking a radiograph will be enough to show you the outline of the dilated esophagus. Fluoroscopy is valuable in more subtle
Image 5: An esophageal stricture is the cause of aspiration pneumonia seen on survey radiographs.
One of the most common causes of focal megaesophagus that I see is esophagitis. It usually occurs in the caudal thoracic esophagus,
and can be a primary disease or secondary to another disorder such as hiatal hernia. This focal dysmotility might be visible
only on fluoroscopy. Liquid barium usually is enough to make the diagnosis of esophagitis using fluoroscopy.
Image 6: An esophageal stricture is the cause of aspiration pneumonia seen on survey radiographs.
Esophageal strictures often are not visible on survey radiographs. You may see only persistent, small collections of air in
the esophagus, and/or aspiration pneumonia (Image 5). Barium and fluoroscopy often are needed to diagnose esophageal strictures,
and to describe their degree of stenosis, location and extent (Image 6). Barium-soaked kibble can be helpful in cases where
there is a mild esophageal stricture. Solid-food particles may slow the bolus in a stenotic area, which is much less obvious
when viewing a liquid bolus.
Even if you have made the diagnosis of megaesophagus on plain radiographs, keep in mind that additional radiographs or fluoroscopy
could be indicated. Imaging is useful in monitoring response to treatment for megaesophagus, or for following secondary disease
such as aspiration pneumonia. Fluoroscopy can help diagnose additional esophageal problems such as dyssynchrony of the pharyngeal
swallowing mechanism or hiatal hernia.
Recognize variations of normal (transient).
Persistent abnormal dilation of the esophagus with gas or fluid.
If static, plain radiographs may be all you need.
Use fluoroscopy in cases of less severe or dynamic disease.
Follow up imaging for response to treatment and monitoring of complications such as aspiration pneumonia.
Dr. Zwingenberger is a veterinary radiologist at the University of California-Davis.