Porth's Essentials of Pathophysiology, 4e

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Gastrointestinal and Hepatobiliary Function

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be confirmed by esophageal pH probe studies or barium fluoroscopic esophagography. In severe cases, esopha- goscopy may be used to demonstrate reflux and obtain a biopsy. Various treatment methods are available for infants and children with gastroesophageal reflux. Small, fre- quent feedings are recommended because of the asso- ciation between gastric volume and transient relaxation of the esophagus. Thickening an infant’s feedings with cereal tends to decrease the volume of reflux, decrease crying and energy expenditure, and increase the calo- rie density of the formula. 13 In infants, positioning on the left side seems to decrease reflux. In older infants and children, raising the head of the bed and keeping the child upright may help. Medications usually are not added to the treatment regimen until pathologic reflux has been documented by diagnostic testing. Antacids are the most commonly used antireflux therapy and are readily available over the counter. H 2 -receptor antago- nists and proton pump inhibitors may be used in chil- dren with persistent reflux. Prokinetic agents (e.g., metoclopramide, a dopamine-2 and 5-hydroxytrypta- mine [5-HT 3 ] receptor antagonist; bethanechol, a cho- linergic agonist) may be used in selected cases. Cancer of the Esophagus Worldwide, the incidence of esophageal cancer var- ies widely, undoubtedly reflecting environmental and dietary influences. It is relatively uncommon in the United States, accounting for about 2% of cancer deaths. 7 There are two types of esophageal cancer: ade- nocarcinoma and squamous cell carcinoma. 6,7,15 Adenocarcinomas typically arise in a background of Barrett esophagus and long-standing GERD. They usu- ally occur in the distal third of the esophagus and may invade adjacent areas of the stomach. Risk of adenocar- cinoma is greater in those with documented esophageal dysplasia and is further increased by tobacco use, obe- sity, and prior radiation therapy. Esophageal carcinomas occur more frequently in Caucasians and are seven times more common in men than women. 6 Molecular stud- ies have suggested that the pathogenesis of adenocar- cinoma from Barrett esophagus is a multistep process, with the development of dysplasia being a critical step in the process. 6 Thus, endoscopic surveillance of persons with Barrett esophagus provides the means for detect- ing adenocarcinoma at an earlier stage, when it is most amenable to curative surgical resection. 15 In contrast to adenomas, squamous carcinomas tend to occur in the middle of the esophagus. Risk factors include alcohol and tobacco use, esophageal injury, achalasia, and frequent consumption of very hot beverages. 6 The regions with the highest incidences are Iran, central China, Hong Kong, Brazil, and South Africa. 6 The majority of esopha- geal squamous carcinomas in Europe and the United States are at least partially attributable to alcohol and tobacco use. However, this form of cancer is also common in areas where alcohol and tobacco use are uncommon. Thus, nutritional deficiencies, as well as polycyclic

hydrocarbons, nitrosamines, and other mutagenic com- pounds such as those found in fungus-contaminated food may be important contributing factors. 6 Dysphagia is by far the most frequent complaint of persons with esophageal cancer. It is apparent first with ingestion of bulky food, later with soft food, and finally with liquids. Unfortunately, it is a late manifestation of the disease. Unintentional weight loss, anorexia, fatigue, and pain on swallowing also may occur. Treatment of esophageal cancer depends on tumor stage. 15 Surgical resection provides a means of cure when done in early disease and palliation when done in late disease. Radiation may be used as an alternative to surgery. Chemotherapy may be used before surgery to decrease the size of the tumor or it may be used along with irradiation and surgery in an effort to increase survival. The prognosis for persons with cancer of the esophagus, although poor, has improved. Even with modern forms of therapy, however, the long-term sur- vival is limited because, in many cases, the disease has already metastasized by the time the diagnosis is made. ■■ The esophagus is a fixed muscular tube through which swallowed food and liquids move as they pass from the pharynx to the stomach. Dysphagia refers to difficulty in swallowing; it can result from altered neuromuscular function or from disorders that produce narrowing of the esophagus. Achalasia is an incomplete relaxation of the lower esophageal sphincter during swallowing. ■■ A diverticulum of the esophagus is an outpouching of the esophageal wall caused by a weakness of the muscularis layer. ■■ Hiatal hernia is characterized by a protrusion or herniation of the stomach through the esophageal hiatus of the diaphragm.There are two anatomic patterns of herniation: the sliding or more common type, in which there is a bell-shaped protrusion of the stomach above the diaphragm, and the paraesophageal hernia, in which a portion of the stomach enters the thorax through a widened opening. ■■ Gastroesophageal reflux refers to the backward movement of gastric contents into the esophagus, a condition that causes heartburn. Persistent reflux of gastric contents into the esophagus can result in a condition called gastroesophageal reflux disease (GERD). Complications of GERD, which result from erosion and/or irritation of the mucosal surface of the esophagus, include esophagitis, strictures of the esophagus, and Barrett esophagus. SUMMARY CONCEPTS