Porth's Essentials of Pathophysiology, 4e

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Disorders of Gastrointestinal Function

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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.

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.