C h a p t e r 2 9
Disorders of Gastrointestinal Function
697
the stomach.
3
The lower esophageal sphincter is a physi-
ologic rather than a true anatomic sphincter. That is,
it acts as a valve, but the only structural evidence of a
sphincter is a slight thickening of the circular smooth
muscle. The smooth muscle fibers in this portion of the
esophagus normally remain tonically constricted except
at times when a bolus of food is about to pass into the
stomach or if a person is vomiting.
2
The lower esopha-
geal sphincter passes through an opening, or
hiatus,
in
the diaphragm as it joins with the stomach, which is
located in the abdomen. The portion of the diaphragm
that surrounds the lower esophageal sphincter helps to
maintain the zone of high pressure needed to prevent
reflux of stomach contents.
Disorders of Esophageal Structure
and Function
The musculature of the pharyngeal wall and upper third
of the esophagus is striated muscle, innervated by the
glossopharyngeal and vagus nerves. The lower two
thirds of the esophagus is smooth muscle, innervated by
the vagus nerve. The act of swallowing depends on the
coordinated action of the tongue, pharyngeal structures,
and esophagus (see Chapter 28).
In general, swallowing can be divided into three
stages (see Chapter 28, Fig. 28-6). The first, or volun-
tary, stage occurs in the mouth. Once the food has been
chewed and well mixed with saliva, the bolus (food
mass) is forced into the pharynx by the tongue. The
second stage, the involuntary pharyngeal–esophageal
phase, transports food through the pharynx and into
the esophagus. The parasympathetic nervous system
(primarily the vagus) controls this part of swallow-
ing and promotes motility of the gastrointestinal tract
from this point on. Once food reaches the distal end
of the esophagus, it passes through the lower esopha-
geal sphincter into the stomach (stage 3). The act of
swallowing is complicated by the fact that the pharynx
subserves respiration as well swallowing. Thus, it is
important that breathing not be compromised because
of swallowing.
Swallowing Disorders
Difficulty swallowing, often referred as
dysphagia
, can
result from disorders that produce narrowing of the
esophagus, lack of salivary secretion, weakness of the
muscular structures that propel the food bolus, or disrup-
tion of the neural networks coordinating the swallowing
mechanism. Lesions of the central nervous system (CNS),
such as a stroke, often involve the cranial nerves that con-
trol swallowing. Cancer of the esophagus and strictures
resulting from scarring can reduce the size of the esopha-
geal lumen and make swallowing difficult. Scleroderma,
an autoimmune disease that causes fibrous replacement
of tissues in the muscularis layer of the gastrointestinal
tract, is another important cause of dysphagia.
4,5
Persons
with dysphagia usually complain of choking, coughing,
or an abnormal sensation of food sticking in the back of
the throat or upper chest when they swallow.
The term
achalasia
means “failure to relax” and in
the context of esophageal function denotes an incom-
plete relaxation of the lower esophageal sphincter in
relation to swallowing. In primary achalasia, the mes-
enteric ganglia that carry the vagal fibers for the lower
esophagus are usually absent from the body of the
esophagus. The condition usually becomes manifest
in young adulthood, but may appear in infancy and
childhood. Achalasia produces functional obstruction
of the esophagus so that food has difficulty passing
into the stomach and the esophagus above the lower
esophageal sphincter becomes distended. Stasis of
food may produce inflammation and ulceration prox-
imal to the lower esophageal sphincter, and there is
danger of aspiration of esophageal contents into the
lungs when the person lies down. The most serious
aspect of the condition is the potential for developing
esophageal cancer.
Treatment of swallowing disorders depends on the
cause and type of altered function that is present.
Treatment often involves a multidisciplinary team of
health professionals, including a speech therapist.
Mechanical dilation or surgical procedures may be done
to enlarge the lower esophageal sphincter in persons
with esophageal strictures.
Esophageal Diverticula
A diverticulum of the esophagus is an outpouching
of the esophageal wall caused by a weakness of the
muscularis layer or motility problems (e.g., diffuse
esophageal spasm, achalasia).
6,7
Esophageal diver-
ticula tend to retain food. Complaints that the food
stops before it reaches the stomach are common, as
are reports of gurgling, belching, coughing, and foul-
smelling breath. The trapped food may cause esopha-
gitis and ulceration. Surgery is the optimal treatment
for persons with severe symptoms or pulmonary
complications.
Esophageal Lacerations
Longitudinal lacerations in the esophagus, also called
Mallory-Weiss syndrome,
represent nonpenetrating
mucosal tears at the gastroesophageal junction.
6–8
They
are most often encountered in persons with chronic
alcoholism after a bout of severe retching or vomit-
ing, but may also occur during acute illness with severe
vomiting. The presumed pathogenesis is inadequate
relaxation of the esophageal sphincter during vomit-
ing, with stretching and tearing of the esophageal junc-
tion during propulsive expulsion of gastric contents.
The tears, which range in length from millimeters to
a few centimeters, usually cross the gastroesophageal
junction and also may be located in the proximal gas-
tric mucosa. Esophageal lacerations account for about
10% of all upper gastrointestinal bleeding, which
often presents as hematemesis.
6
Most often bleeding is
not severe and does not require surgical intervention.
Healing is usually prompt, with minimal or no residual
effects.
