Chapter 12 The Gastrointestinal System
1 What is the basic structure of the gastrointestinal (GI) system?
The entire GI tract has a relatively uniform structure and consists of four layers:
2 What are the main diseases of the GI system?
3 Discuss the possible consequences of abnormal development of the GI system
4 What are the main clinical symptoms and signs of esophageal disease?
5 What is the most common developmental abnormality of the esophagus?
Esophageal atresia with tracheoesophageal fistula is the most common developmental abnormality. Several anatomic variants are recognized. Food cannot pass into the stomach because the lumen of the esophagus ends in a blind pouch. Food passing through the fistula enters the trachea, causing choking and coughing. Symptoms appear soon after birth, requiring immediate surgical correction.
6 What are esophageal diverticula?
Diverticula are outpouchings of the wall of the esophagus. These outpouchings are classified on the basis of the following (Fig. 12.1):
7 Define achalasia
Achalasia is a functional disorder characterized by a loss of normal esophageal peristalsis and incomplete or abnormal relaxation of the lower esophageal sphincter (LES). The LES must relax during swallowing, but if it does not and remains contracted, it will act as a barrier to the food destined to enter the stomach. Secondary dilatation of the aperistaltic esophagus proximal to the constriction occurs.
The cause of primary achalasia, a rare disease (1:100,000), is not known. Histologic studies show, however, that the spasm of the LES is associated with a loss of ganglion cells from the lower esophagus. Secondary achalasia may occur in Chagas disease because of the destruction of ganglion cells infected with Trypanosoma cruzi.
8 What are esophageal webs and rings?
Webs are mucosal folds causing narrowing of the lumen. Dysphagia caused by webs in the upper esophagus may be associated with glossitis and iron deficiency anemia (Plummer–Vinson syndrome). The disease is common in Scandinavian countries but rare in the United States.
Schatzki ring is a subepithelial semicircular fibrous strand in the wall of the esophagus. It narrows the lumen at the gastroesophageal junction. It may cause dysphagia and is best demonstrated by esophagoscopy.
9 What is hiatal hernia?
Hiatal hernia is a protrusion of the stomach above the diaphragm through a widened diaphragmatic hiatus. Hiatal hernias are quite common. Two forms are recognized (Fig. 12-2):
10 What is congenital diaphragmatic hernia?
Congenital diaphragmatic hernia is a severe developmental defect in which the diaphragm is defective or incompletely developed. Abdominal organs dislocate through the defect into the thoracic cavity, compressing the lung and the heart. The condition is often associated with other developmental abnormalities and is usually lethal. Minor diaphragmatic defects may be repaired surgically.
11 What is GERD?
Reflux of gastric contents into the esophagus is a common disorder, typically associated with incompetence of the LES. It presents with odynophagia and dysphagia and may even cause hemorrhage. The diagnosis is suspected on the basis of typical clinical presentation and is confirmed by esophagoscopy. Esophageal biopsy may be performed during endoscopy to document the extent of inflammation or ulceration and to determine whether Barrett esophagus (with or without dysplasia) has developed.
12 Discuss the causes of GERD
GERD develops because of malfunction of the LES, which in normal circumstances prevents the entry of the gastric contents into the esophagus. Reflux may be caused by:
13 List the most common complications of GERD
Complications of long-lasting GERD are:
14 What is the etiology of esophagitis?
Three major etiologic groups are recognized:
15 What are the causes of infectious esophagitis?
The esophagus is covered by squamous epithelium, which is relatively resistant to infections. Most infections occur in people with poor health, systemic disease, or those with reduced immune response. A breach in the mucosal barrier (e.g., in GERD) may allow infection to take place. The most common infections are:
16 What are the most common forms of chemical esophagitis?
17 What is Barrett esophagus?
Barrett esophagus is a form of metaplasia of the esophagus. Typically, it involves the lower segment of the esophagus and is thought to be most often caused by GERD. It can be recognized on endoscopy and biopsy:
18 What is the significance of Barrett esophagus?
Barrett esophagus is associated with a variety of clinical symptoms, most often odynophagia. The esophagus may ulcerate and bleed. The most important complication of Barrett esophagus is adenocarcinoma of the esophagus, which develops in a significant number of cases (10%).
19 Which pathologic changes precede adenocarcinoma in Barrett esophagus?
Adenocarcinoma developing in Barrett esophagus is typically preceded by histologically recognizable dysplasia. Pathologists classify such dysplasia as mild or severe. Severe dysplasia must be followed up clinically in every case, and partial resection of the esophagus is recommended in some instances because such dysplasia has a propensity to progress to invasive adenocarcinoma.
20 What is Mallory–Weiss syndrome?
Mallory–Weiss syndrome is characterized by bleeding from esophageal lacerations that develop because of violent retching. It is typically encountered in chronic alcoholics.
21 List key facts about esophageal varices
22 How common is esophageal cancer?
Esophageal cancer is not common in the United States, but it is a disproportionately high cause of cancer-related deaths. The incidence of esophageal cancer is increasing in the United States:
23 List the risk factors for esophageal cancer
24 Which part of the esophagus is most often affected by carcinoma?
Most esophageal carcinomas develop in the midportion or the lower third of the esophagus. The upper third of the esophagus is least commonly involved.
25 Describe the gross appearance of esophageal carcinoma
Esophageal carcinoma typically narrows the lumen of the esophagus or affects peristalsis, thus causing dysphagia. On gross examination, tumors may present as:
26 How are esophageal carcinomas classified histologically?
27 What is the most important developmental disorder of the stomach?
Congenital hypertrophic pyloric stenosis affects 1 in 400 to 600 infants. The disease shows a multifactorial pattern of inheritance, but it may also be associated with chromosomal developmental disorders (e.g., Turner syndrome). Typically, it presents with projectile vomiting. It is caused by hypertrophy of the smooth muscle in the pyloric portion of the stomach, which may be palpated through the abdominal wall. Surgical incision provides relief and is routinely performed with excellent results.
28 What is gastritis?
Gastritis is an inflammation of the mucosa of the stomach. It is a common disease that may occur in an acute or a chronic form. Morphologically, acute gastritis typically presents with shallow erosions of the mucosa (erosive gastritis). Chronic gastritis may be erosive or nonerosive.
29 What are the most common causes of acute gastritis?
Acute erosive gastritis is a self-limited inflammation of the gastric mucosa. Clinically, it presents with epigastric burning, pain, nausea, and vomiting. Variable amounts of blood may be found in the vomitus. Pathologically it is characterized by shallow blood-suffused mucosal erosions surrounded by acute inflammatory cells. These mucosal changes may be caused by:
30 Discuss why gastric erosions develop in acute gastritis
Erosions may develop because of the direct effects of a potentially toxic substance (e.g., alcohol), oversecretion or back-diffusion of hydrochloric acid, or a breakdown of the local mucosal defense system against the corrosive action of gastric juice. For example, hypoperfusion of the gastric mucosa in shock makes the mucosal cells more susceptible to the action of pepsin and hydrochloric acid. Aspirin and NSAIDs inhibit the local synthesis of prostaglandins and weaken the mucosal defense system.
31 What are Cushing and Curling ulcers?
These eponyms are used for gastric stress ulcers. Such ulcers are deeper than erosions and may extend all the way to the muscularis mucosae. Cushing (who was a famous neurosurgeon) gave his name to ulcers caused by brain injury. Curling ulcers are found in burn patients. (An easy way to remember which is which is to think “things curl in fire.”)
32 Describe the main forms of chronic nonerosive gastritis
Chronic nonerosive gastritis is inflammation of the mucosa of the stomach that may be caused by immunologic mechanisms, infection, and prolonged ingestion of drugs or alcohol or cigarette smoking. Several clinicopathologic forms of chronic gastritis are recognized:
33 Is it possible to distinguish type A and type B chronic gastritis in biopsy material examined microscopically?
Type A is an autoimmune disease, whereas type B is an infectious disease caused by H. pylori. In early stages of the disease, it is possible to distinguish type A from type B gastritis histologically, but in advanced stages, such a distinction is not always possible.
In the early stages of autoimmune gastritis, the mucosa of the fundus and body is infiltrated with lymphocytes and plasma cells. Acute stages of H. pylori infection are associated with infiltrates of neutrophils in the glands and the lamina propria. H. pylori can be seen in the gastric glands, mostly in the pyloric antrum. As the diseases progress, both forms of chronic gastritis are accompanied by:
In this advanced stage of the disease, it is difficult to find H. pylori, which does not survive in the metaplastic intestinal glands. Reliable histopathologic distinction of type A from type B chronic gastritis becomes impossible in the disease’s later stages.
34 Is it possible to clinically distinguish type A from type B chronic gastritis?
As stated previously, the histologic diagnosis of type B chronic gastritis depends primarily on finding H. pylori in the gastric biopsies. Because the gastroscopic findings are similar in both forms of gastritis and H. pylori cannot always be found in advanced stages of the disease, other tests (e.g., urea breath test or antibody test for H. pylori) must be performed. The most important aspects of type A and type B gastritis useful for distinguishing one form of gastritis from the other are listed in Table 12-1.
|Feature||Type A Gastritis*||Type B Gastritis|
|Distribution of lesions||Fundus, diffuse||Pyloric antrum, focal|
|Gastric secretion||Reduced||Normal, +, or −|
|Antibodies to parietal cells||Yes||No|
|Other autoimmune diseases||Yes||No|
|Vitamin B12 (in serum)||Low||Normal|
|Gastrin (in serum)||Increased||Normal|
|Antibodies to Helicobacter pylori||−||+|
|Incidence||Less common||More common|
* Type A gastritis is associated with four As: autoimmune disease, antibodies to pyloric cells, anemia (pernicious), and achlorhydria (reduced hydrochloric acid secretion).
35 Which form of chronic gastritis is associated with a higher risk of cancer?
Type A gastritis is associated with a higher relative risk of gastric adenocarcinoma. However, because type B chronic gastritis is much more prevalent, it is thought to be the cause of many more cancers than type A gastritis. In this context, it is worth noting that the World Health Organization has designated H. pylori as a potential human carcinogen. Epidemiologic data link H. pylori to an increased incidence of gastric adenocarcinoma and lymphoma in many areas of the world, especially southern Europe, South America, and Asia.
36 Explain the pathogenesis of peptic ulcer
The pathogenesis of peptic ulcers is not fully understood. It is, however, generally accepted that the mucosal ulcerations are chemically mediated and develop because of the action of HCl and pepsin on a “weakened” or “susceptible” gastric or duodenal mucosa. Because the gastric acid of ulcer patients does not contain unusually high quantities of HCl or pepsin, it is postulated that the glands are damaged by a back-diffusion of hydrogen ions.
37 Which factors play a role in the development of peptic ulcers?
Peptic ulcer is a multifactorial disease, and several factors contribute to its pathogenesis: