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Motility Disorders of the Alimentary Tract

1
Reto Neiger, Dr. Med Vet, PhD, DACVIM (SAIM), DECVIM-CA
and Silke Salavati, Dr. Med Vet, PhD, DipECVIM-CA, MRCVS 2
1 Small Animal Clinic Hofheim, Hofheim, Germany
2 Royal School of Veterinary Studies, University of Edinburgh, Edinburgh, Scotland

Gastrointestinal (GI) motility disorders are a diagnostic a complex reflex is instituted, that starts with cri-
and therapeutic challenge. They can consist of delayed or copharyngeal relaxation. The food bolus is then passed
accelerated transit times as well as impaired or inappro- through the UES into the cervical esophagus. Immediately
priate relaxation anywhere in the GI tract. Delayed tran- thereafter, the UES closes, preventing material from
sit is the most common form. This may be a primary entering the trachea or being pushed back into the phar-
localized neuromuscular disorder, part of a more gener- ynx. Continuous peristaltic contractions move the food
alized GI motility disturbance (e.g., dysautonomia) or aborally, where it passes through the relaxed GES (pri-
secondary to systemic health problems (metabolic, toxic, mary esophageal peristalsis). In a case where the first
inflammatory, neoplastic, obstructive, etc.). peristaltic wave is inadequate for complete transport,
secondary esophageal peristalsis occurs, where local
esophageal distension generates another peristaltic wave.
Motility Disorders of the Esophagus
Clinical Signs of Esophageal Motility Disorders
Physiology of Esophageal Motility
The classic clinical sign of esophageal disease is regurgi-
The esophagus acts as a simple tube for the transport of tation. Additional common complaints are dysphagia,
food from the oral cavity to the stomach. Between swal- hypersalivation, retching and gagging, odynophagia, and
lows, it is collapsed but can distend markedly to accom- repeated swallowing attempts. Less common signs are
modate a food bolus. Structurally, it is of similar anorexia and lethargy. Both dogs and cats can show signs
composition to the remainder of the GI tract, but it lacks of aspiration pneumonia (fever, tachypnea, coughing,
a serosa. In dogs, the muscular layer (responsible for the dyspnea).
motor function) is composed of two layers of striated On physical examination, low body condition score/
muscles spiraling in oblique bundles and crossing each weight loss or poor growth might be apparent. Rarely, a
other at right angles. In cats, there is a transition zone dilated esophagus can be palpated in the cervical region.
from striated to smooth muscle at the level of the heart. Bradycardia, loss of pupillary light reflexes, decreased
There are two sphincters: the upper esophageal tear production (demonstrated by a Schirmer tear test),
sphincter (UES), consisting of the cricopharyngeus mus- dry mucous membranes, and constipation/diarrhea in
cle, and the gastroesophageal sphincter (GES), which is a combination with megaesophagus are indicative of a
thickening of the esophageal muscle at the junction to dysautonomia.
the stomach.
Esophageal transport of a food bolus – as part of the Causes of Esophageal Motility Disorders
complicated swallowing act – is under complete auto-
nomic neuronal control. Efferent neurons from the In small animals, primary esophageal motor dysfunction
nucleus ambiguous in the medulla oblongata innervate is poorly defined and infrequently recognized, except for
the striated muscle (dogs and cats) and the smooth idiopathic megaesophagus and esophageal diverticula in
muscle (cats) via the vagus nerve. Once the food bolus dogs. A high prevalence of subclinical primary esopha-
is voluntarily pushed caudally into the oropharynx, geal dysmotility has been reported in certain dog breeds

Clinical Small Animal Internal Medicine Volume I, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical