91731_ch13 12/8/06 8:55 PM Page 549 13 The Gastrointestinal Tract Frank A. Mitros Emanuel Rubin THE ESOPHAGUS Bezoars Anatomy THE SMALL INTESTINE Congenital Disorders Anatomy Tracheoesophageal Fistula Congenital Disorders Rings and Webs Atresia and Stenosis Esophageal Diverticula Duplications (Enteric Cysts) Motor Disorders Meckel Diverticulum Achalasia Malrotation Scleroderma Meconium Ileus Hiatal Hernia Infections of the Small Intestine Esophagitis Bacterial Diarrhea Reflux Esophagitis Viral Gastroenteritis Barrett Esophagus Intestinal Tuberculosis Eosinophilic Esophagitis Intestinal Fungi Infective Esophagitis Parasites Chemical Esophagitis Vascular Diseases of the Small Intestine Esophagitis of Systemic Illness Acute Intestinal Ischemia Iatrogenic Cancer of Esophagitis Chronic Intestinal Ischemia Esophageal Varices Malabsorption Lacerations and Perforations Luminal-Phase Malabsorption Neoplasms of the Esophagus Intestinal-Phase Malabsorption Benign tumors Laboratory Evaluation Carcinoma Lactase Deficiency Adenocarcinoma Celiac Disease THE STOMACH Whipple Disease Anatomy AbetalipoproteinemiaHypogammaglobulinemia Congenital Disorders Congenital Lymphangiectasia Pyloric Stenosis Tropical Sprue Diaphragmatic Hernia Radiation Enteritis Rare Abnormalities Mechanical Obstruction Gastritis Neoplasms Acute Hemorrhagic Gastritis Benign Tumors Chronic Gastritis Malignant Tumors MénétrierDisease Pneumatosis Cystoides Intestinalis Peptic Ulcer Disease THE LARGE INTESTINE Benign Neoplasms Anatomy Stromal Tumors Congenital Disorders Epithelial Polyps Congenital Megacolon (Hirschsprung Disease) Malignant Tumors Acquired Megacolon Carcinoma of the Stomach Anorectal Malformations Neuroendocrine Tumors Gastric Lymphoma Gastrointestinal Stromal Tumors 549 91731_ch13 12/8/06 8:55 PM Page 550 550 Pathology Infections of the Large Instestine Miscellaneous Disorders Pseudomembranous Colitis Endometriosis Neonatal Necrotizing Enterocolitis Melanosis Coli Diverticular Disease Gastroinstestinal Infections as Complications of AIDS Diverticulosis THE APPENDIX Diverticulitis Anatomy Inflammatory Bowel Disease Appendicitis Crohn Disease Mucocele Ulcerative Colitis Neoplasms Collagenous Colitis and Lymphocytic Colitis THE PERITONEUM Vascular Diseases Peritonitis Ischemic Colitis Bacterial Peritonitis Angiodysplasia (Vascular Ectasia) Chemical Peritonitis Hemorrhoids Familial Paroxysmal Polyserositis (Familial Mediterranean Radiation Enterocolitis Fever) Solitary Rectal Ulcer Syndrome Retroperitoneal Fibrosis Polyps of the Colorectum Neoplasms of the Peritoneum Adenomatous Polyps Mesenteric and Omental Cysts Hyperplastic Polyps Mesotheliomas Variants of Hyperplastic Polyps Primary Peritoneal Carcinoma Familial Adenomatous Polyposis Metastatic Carcinoma Non-neoplastic Polyps Malignant Tumors Adenocarcinoma of the Colon and Rectum Carcinoid Tumors Large Bowel Lymphoma Cancers of the Anal Canal The venous drainage of the esophagus is important in portal THE ESOPHAGUS hypertension, in which esophageal varices occur. These varices are invariably found in the lower third of the esophagus, because Anatomy the veins of the upper third drain into the superior vena cava and those of the middle third drain into the azygous system. Only the Embryologically, the gut and respiratory tract arise from the veins of the lower third of the esophagus drain into the portal same anlage and constitute a single tube. This structure divides vein via the gastric veins. into two separate tubes, the esophagus being dorsal and the fu- ture respiratory tract, ventral. Initially, columnar epithelium lines the esophagus in its early embryonic development, but it is replaced by a stratified squamous epithelium. Congenital Disorders The adult esophagus is a 25-cm tube that is a conduit for the passage of food and liquid into the stomach. It contains striated Tracheoesophageal Fistula Leads to Aspiration and smooth muscle in its upper portion and smooth muscle Pneumonia alone in its lower portion. The organ is fixed superiorly at the Tracheoesophageal fistula is the most common esophageal cricopharyngeus muscle, which is considered the upper anomaly (Fig. 13-1). It is frequently combined with some form of esophageal sphincter. It courses inferiorly through the posterior esophageal atresia. In some cases, it is associated with a com- mediastinum behind the trachea and heart, and exits the thorax plex of anomalies identified by the acronym Vater syndrome through the hiatus of the diaphragm. Tonic muscular contrac- (vertebral defects, anal atresia, tracheoesophageal fistula, and re- tion at its lower end creates an action like that of a one-way flut- nal dysplasia). Maternal hydramnios has been recorded in some ter valve. The so-called lower esophageal sphincter is not a true cases of esophageal atresia and, less commonly, in cases of tra- anatomical sphincter but rather a functional one. cheoesophageal fistula. Esophageal atresia and fistulas are often The esophagus has a mucosa, submucosa, muscularis pro- associated with congenital heart disease. pria, and adventitia. The transition from the squamous mucosa of the esophagus to the gastric mucosa at the esophagogastric PATHOLOGY: In 90% of tracheoesophageal fistulas, junction occurs abruptly at the level of the diaphragm. The the upper portion of the esophagus ends in a blind esophageal submucosa contains mucous glands and a rich lym- pouch and the superior end of the lower segment com- phatic plexus. The lymphatics of the upper third of the esopha- municates with the trachea. In this type of atresia, the upper blind gus drain to cervical lymph nodes, those of the middle third to sac soon fills with mucus, which the infant then aspirates. Surgical the mediastinal nodes, and those of the lower third to the celiac correction is feasible albeit difficult. and gastric lymph nodes. These anatomic features are significant Among the remaining 10% of fistulas, the most common is a in the spread of esophageal cancer. communication between the proximal esophagus and the 91731_ch13 12/8/06 8:55 PM Page 551 CHAPTER 13: THE GASTROINTESTINAL TRACT 551 the hypopharyngeal area above the upper esophageal sphincter, in the middle esophagus, and immediately proximal to the lower esophageal sphincter. Esophagus ZENKER DIVERTICULUM: Zenker diverticulum is an uncom- mon lesion that appears high in the esophagus and affects men more Trachea than women. It was once believed to result from luminal pressure exerted in a structurally weak area and was therefore classed as a pulsion diverticulum. The cause is probably more compli- cated, but disordered function of cricopharyngeal musculature is ABstill generally thought to be involved in the pathogenesis of this false diverticulum. Most affected persons who come to medical attention are older than 60, suggesting that this diverticulum is acquired. Zenker diverticula can enlarge conspicuously and accumu- late a large amount of food. The typical symptom is regurgita- tion of food eaten some time previously (occasionally days), in the absence of dysphagia. Recurrent aspiration pneumonia may be a serious complication. When symptoms are severe, surgical intervention is the rule. C TRACTION DIVERTICULA: Traction diverticula are outpouch- FIGURE 13-1. Congenital tracheoesophageal fistulas. A. The most ings that occur principally in the midportion of the esophagus. They common type is a communication between the trachea and the lower por- were so named because of their attachment to adjacent medi- tion of the esophagus. The upper segment of the esophagus ends in a astinal lymph nodes, usually associated with tuberculous lym- blind sac. B. In a few cases, the proximal esophagus communicates with phadenitis. However, such adhesions are today uncommon and the trachea. C. The least common anomaly, the H type, is a fistula be- it is believed that these pouches often reflect a disturbance in the tween a continuous esophagus and the trachea. motor function of the esophagus. A diverticulum in the mides- ophagus ordinarily has a wide stoma and the pouch is usually higher than its orifice. Thus, it does not retain food or secretions trachea; the lower esophageal pouch communicates with the and remains asymptomatic, with only rare complications. stomach. Infants with this condition develop aspiration immediately EPIPHRENIC DIVERTICULA: These diverticula are located im- after birth. In another variant, termed an H-type fistula, a commu- mediately above the diaphragm. Motor disturbances of the esopha- nication exists between an intact esophagus and an intact tra- gus (e.g., achalasia, diffuse esophageal spasm) are found in two chea. In some cases, (see Fig. 13-1C) the lesion becomes symp- thirds of patients with this true diverticulum. In addition, reflux tomatic only in adulthood, when repeated pulmonary infections esophagitis may play a role in the pathogenesis of epiphrenic di- call attention to it. verticula. Unlike other diverticula, epiphrenic diverticula are en- Rings and Webs Cause Dysphagia countered in young persons. Nocturnal regurgitation of large ESOPHAGEAL WEBS: Occasionally, a thin mucosal membrane amounts of fluid stored in the diverticulum during the day is projects into the esophageal lumen. Webs are usually single, but may be multiple, and can occur anywhere in the esophagus. They are often successfully treated by dilation with large rubber bougies; occasionally, they can be excised with biopsy forceps during endoscopy. PLUMMER-VINSON (PATERSON-KELLY) SYNDROME: This disorder is characterized by (1) a cervical esophageal