Page 1275 - Cote clinical veterinary advisor dogs and cats 4th

642 Megaesophagus

• Rotating a patient while attached to anes- after the procedure, alert the attending clini- SUGGESTED READING
thetic circuit • Dogs that present with edema confined Pintore L, et al: Cytological and histological correla-
cian as soon as possible.
VetBooks.ir Technician Tips to the face, neck, and forelimbs may have AUTHOR: Graham Swinney, BVSc, DVCS, FACVSc
• Traumatic jugular venipuncture
tion in diagnosing feline and canine mediastinal
masses. J Small Anim Pract 55:28-32, 2014.
mediastinal disease.
• Complications of fine-needle aspiration of a
mediastinal mass include pneumothorax and • Cats with mediastinal masses can be fragile EDITOR: Megan Grobman, DVM, MS, DACVIM
(unstable respiratory/cardiovascular status).
hemothorax. If a patient suddenly develops Minimize handling, and avoid ventrodorsal
tachypnea and/or increased respiratory effort projection for thoracic radiographs.

Megaesophagus Client Education
Sheet

BASIC INFORMATION HISTORY, CHIEF COMPLAINT • Muscular (e.g., polymyositis, muscular
• Regurgitation (distinguish from vomiting) dystrophy)
Definition is the most common complaint. Other causes of megaesophagus include certain
Esophageal dilation due to muscular weakness • Cough (due to aspiration): sometimes seen metabolic conditions (e.g., hypoadrenocorti-
from any cause, which must be distinguished before regurgitation is reported cism). Megaesophagus may also occur orad to
from esophageal dilation orad to an obstruction • Drooling (due to difficulty swallowing) esophageal obstruction (e.g., lower esophageal
sphincter dysfunction/obstruction, persistent
Synonyms PHYSICAL EXAM FINDINGS right aortic arch).
Acquired esophageal weakness, congenital • Pulmonary crackles/easily elicited cough (due
esophageal weakness to aspiration pneumonia) DIAGNOSIS
• Fever and signs of systemic illness (e.g.,
Epidemiology anorexia, lethargy) with severe aspiration Diagnostic Overview
SPECIES, AGE, SEX pneumonia Megaesophagus is a differential for any
• Dogs and cats (less commonly) of any age • Bellows-like action at thoracic inlet, associ- regurgitating patient. It is important to dif-
or sex ated with breathing (due to filling and ferentiate vomiting from regurgitation; careful
• Acquired megaesophagus usually occurs after emptying of distended esophagus with air) history taking helps but is not always accurate.
2-3 years of age. • Nasal discharge (with pneumonia or rhinitis Thoracic radiographs confirm megaesophagus
secondary to regurgitation) in many cases, but some patients, especially
GENETICS, BREED PREDISPOSITION • Weight loss or failure to gain weight (if those with segmental megaesophagus of the
• Congenital megaesophagus patient is losing excessive calories or has cervical region, require contrast esophagrams.
○ Cats: Siamese chronic pulmonary infection) Additional diagnostic tests are appropriate
○ Dogs: German shepherds, Great Danes, to look for underlying causes that present
Labrador retrievers, miniature schnauzers, Etiology and Pathophysiology therapeutic opportunities.
Irish setters, Shar-peis, fox terriers, New- Congenital or idiopathic megaesophagus:
foundlands, but any dog can be affected • A defect in any part of the neuromuscular Differential Diagnosis
• Acquired megaesophagus in dogs: any dog reflex that controls the pharyngeal and Acquired megaesophagus in the dog:
can be affected esophageal phases of swallowing, including • Myasthenia gravis (generalized or localized):
sensory receptors, afferent nerves (glossopha- most common identified cause
RISK FACTORS ryngeal and vagus), tractus solitarius (leading • Hypoadrenocorticism
Any cause of lower motor neuron weakness to the nucleus solitarius), swallowing center • Dysautonomia (uncommon except in areas
can produce acquired megaesophagus if the (near the lateral reticular formation), lower of the Midwest)
esophageal muscles are affected. Myasthenia motor neurons of the nucleus ambiguus, • Polymyopathies/polyneuropathies
gravis, hypoadrenocorticism, and dysautonomia efferent somatic and parasympathetic nerve • Lead intoxication (rare)
are risk factors (feline dysautonomia, or Key- fibers in the vagus, myoneural junction in • Organophosphate intoxication (rare)
Gaskell syndrome, is now rare). the esophagus, esophageal striated muscle, • Botulism or tetanus (rare)
and potentially esophageal smooth muscle • Esophagitis (rare cause of megaesophagus)
ASSOCIATED DISORDERS in the cat • Systemic lupus erythematosus (rare)
• Coughing due to tracheobronchitis or • Defect probably resides in the afferent limb • Dermatomyositis (primarily collies and
aspiration pneumonia of the reflex arc. This is supported by the Shetland sheepdogs)
• Death from aspiration pneumonia (most fact that dogs with megaesophagus are prone • Idiopathic (most common category)
common cause) to aspiration pneumonia, which is increased Acquired megaesophagus in the cat:
• In some animals with acquired megaesopha- among dogs with loss of the afferent arc • Dysautonomia (Key-Gaskell syndrome)
gus, generalized weakness due to myopathy, (abnormal respiratory reflexes also occur). • Myasthenia gravis
neuropathy, or junctionopathy Secondary megaesophagus: muscular weakness • Idiopathic (most feline cases)
due to some other lower motor neuron disease:
Clinical Presentation • Neurologic (e.g., polyradiculoneuritis, Initial Database
DISEASE FORMS/SUBTYPES dysautonomia, demyelinating neuropathies, • CBC: look for evidence of inflammation
• Congenital megaesophagus lead) consistent with aspiration pneumonia.
• Acquired megaesophagus can be generalized • Neuromuscular (botulism, tetanus, myasthe- • Plain thoracic radiographs: look for mega-
or segmental (usually the cervical esophagus). nia gravis) esophagus (not always obvious) and for

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