Page 480 - Small Animal Internal Medicine, 6th Edition

452 PART III Digestive System Disorders

Treatment Treatment
Injection of the cricopharyngeal muscle with botulism toxin Cricopharyngeal myotomy is often curative for animals with
VetBooks.ir benefits some patients, and it is believed that these patients cricopharyngeal achalasia but can be disastrous for animals
with pharyngeal dysphagias because it allows food retained
stand to improve the most from cricopharyngeal myotomy,
in the proximal esophagus to more easily reenter the pharynx
whereas those that do not respond to botulinum toxin seem
to respond poorly to surgery. If surgery is performed, be and be aspirated. The clinician must either bypass the
careful not to cause cicatrix at the surgery site. It is critical pharynx (e.g., gastrostomy tube) or resolve the underlying
that this disorder is distinguished from pharyngeal dyspha- cause (e.g., control the myopathy, junctionopathy, or
gia and that esophageal function in the cranial esophagus is neuropathy).
evaluated before surgery is considered (see next section on
pharyngeal dysphagia). Treatment with thyroxine might Prognosis
rarely help some patients. Prognosis is guarded because it is often difficult to charac-
terize and treat the underlying cause, and the dog or cat is
Prognosis prone to progressive weight loss and recurring aspiration
The prognosis is usually good if cicatrix does not occur pneumonia.
postoperatively.
ESOPHAGEAL WEAKNESS/
PHARYNGEAL DYSPHAGIA MEGAESOPHAGUS

Etiology CONGENITAL ESOPHAGEAL WEAKNESS
Pharyngeal dysphagia is primarily an acquired disorder Etiology
with neuropathies, myopathies, and junctionopathies
(e.g., localized myasthenia gravis) seeming to be the main The cause of congenital esophageal weakness (i.e., congenital
causes. Inability to form a normal bolus of food at the base megaesophagus) is uncertain, but a defect in vagal afferent
of the tongue and/or propel the bolus into the esophagus innervation of the esophagus is suspected.
is often associated with lesions of cranial nerves IX or X.
Simultaneous dysfunction of the cranial esophagus may Clinical Features
cause food retention just caudal to the cricopharyngeal Affected animals (primarily dogs) are usually presented
sphincter. because of “vomiting” (actually regurgitation) with or
without weight loss, coughing, or fever from pneumonia.
Clinical Features Occasionally, coughing and other signs of aspiration tra-
Although pharyngeal dysphagia principally is found in cheitis and/or pneumonia may be the only signs reported
adults, younger animals occasionally have transient signs. by the owner. In particularly severe cases, one may see the
Pharyngeal dysphagia often clinically mimics cricopharyn- cervical esophagus balloon in and out during respiration
geal achalasia; regurgitation is associated with swallowing. (Video 29.1).
Pharyngeal dysphagia sometimes causes more difficulty
swallowing fluids than solids. Aspiration (especially associ- Diagnosis
ated with liquids) is common because the proximal esopha- The clinician must first determine from the history that re-
gus is often flaccid and retains food and water, predisposing gurgitation is likely, instead of vomiting (see p. 391). Ra-
to later reflux into the pharynx. diographs showing generalized esophageal dilation without
evidence of obstruction (see Fig. 27.3, A) allow presump-
Diagnosis tive diagnosis of esophageal weakness. If plain thoracic
Fluoroscopic examination of the patient swallowing barium radiographs are not revealing, then static or dynamic bar-
is typically required for diagnosis. An experienced radi- ium contrast radiographs are appropriate because many
ologist is needed to reliably distinguish pharyngeal dys- patients with esophageal weakness do not have abnor-
phagia from cricopharyngeal dysphagia. With the former malities on plain radiographs. Fluoroscopic examination
condition the animal does not have adequate strength is required to distinguish idiopathic congenital esopha-
to push food boluses into the esophagus, whereas in the geal weakness from lower esophageal achalasia; however,
latter the animal has adequate strength but the cricopha- the latter is thought to be very uncommon. The esopha-
ryngeal sphincter stays shut or opens at the wrong time geal deviation normally seen in brachycephalics (Fig. 29.1)
during swallowing, thereby preventing normal movement must not be confused with esophageal pathology. Diver-
of food from the pharynx to the proximal esophagus. ticula in the cranial thorax caused by esophageal weakness
Serum CK may be increased in some patients with myopa- occur occasionally and can be confused with vascular ring
thies. Some causes may be detected by electromyography obstruction (Fig. 29.2). Congenital rather than acquired
of laryngeal, pharyngeal, and esophageal muscles and/or disease is suspected if the regurgitation and/or aspiration
muscle biopsy. began when the pet was young. If clinical features have