Secondary Esophageal Motor Disorders and Treatment
- Secondary esophageal motor disorders are associated with multiple distinct diseases.
- Although rarely life-threatening, they are an important source of morbidity and quality of life issues.
- Treatment strategies are often complicated, in part attributable to the underlying systemic illness.
For such a simple hollow viscus that solely serves to transfer foodstuffs from pharynx to stomach in a unidirectional manner, the esophagus is a surprisingly complex organ. Its unfortified anatomic structure belies its central role at the start of the digestive tract. There are three important anatomic boundaries: 1) the mucosa, consisting of stratified squamous cells with deeper glands, 2) the submucosa, an intervening areolar tissue plane through which course the lymphatic and vascular supply serving the mucosa, and 3) the muscularis (propria), a dense muscular cocoon divided into a thick inner circular layer and a more attenuated outer longitudinal layer. The composition of the muscular layer varies as the organ courses distally, as striated muscle is principally present in the cervical region and there is a gradually transitioning to smooth muscle as the organ courses through the thorax towards the stomach. There is no serosal covering of the organ, underscoring the relative ease with which spontaneous perforation can occur and perhaps why primary malignancy disseminates quickly.
The function of the organ is far more complex than its structure would suggest. The organ must propel food in an aboral direction only, while segmentally distending in a highly coordinated fashion to permit passage of a food bolus. There are manometrically distinct entry (upper esophageal sphincter [UES]) and exit (lower esophageal sphincter [LES]) points that are also regulated with time-related relaxation and contraction initiated by a voluntary swallow. Moreover, the organ must defend itself from retrograde propulsion and gastroesophageal reflux. Herein lies the genius of its construction and orchestration of its function.
The esophagus can be separated into two distinct segments based on function and structure: cervical and thoracic. Though the functional difference between the two seems at first glance to be indistinguishable, and is a seamless integration of peristalsis (initiated voluntarily in the pharynx and cervical esophagus) across the length of the thoracic esophagus involuntarily and there are subtle differences in composition of the muscular component as the organ descends. This allows for unique differences in disease presentation based on the anatomic segment of the esophagus affected and its specific lymphatic drainage pattern. When considering esophageal physiology and derangements thereof, a more practical understanding is best appreciated by considering the esophagus as composed of three functional components: the inlet (UES), esophageal body, and outlet (LES). The vast majority of benign diseases of the esophagus revolve around dysfunction at one or more of these foci. These three regions align anatomically with the cervical, thoracic, and abdominal portions of the esophagus, and consequently, interactions with the unique surrounding environment around each modifies (and can magnify) disease presentation.
Esophageal motility dysfunction classically presents as some variable combination of dysphagia, regurgitation, and atypical chest pain. When this symptom-complex occurs in the setting of a systemic disease or is not directly attributable to one of a number of well-characterized isolated esophageal disorders,, it is then considered a secondary esophageal motor disorder.
The spectrum of diseases associated with secondary esophageal motor disorders can be broadly separated into six categories: rheumatologic (collagen vascular), infectious, other inflammatory, neuropathic, iatrogenic, and cryptogenic. The involvement of the esophagus with each condition is slightly different and clearly warrants independent consideration. Regardless, esophageal motility is affected and, rarely, can become the most important clinical manifestation of the disease.
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