Eighty percent of gastrointestinal (GI) neuroendocrine tumors are made up of enterochromaffin-like cell carcinoids, duodenal gastrin G-cell tumors, and rectal trabecular L-cell carcinoids. Less common neuroendocrine tumors are gangliocytic paragangliomas, somatostatinomas, lipomas, and schwannomas. Pathologic study has revealed that the term carcinoid represents a wide spectrum of neoplasms that originate from different neuroendocrine cells. Carcinoid tumors of the small intestine that secrete serotonin (5-hydroxytryptamine [5-HT]) are…

Malignant tumors of the small intestine are rare. Their frequency in a large autopsy study was lower than 0.1%. Although the small bowel is the largest gastrointestinal organ, less than 5% of malignant tumors arise in the small intestine. The reason for this remains unclear. Adenocarcinoma (nonampullary) is the most common malignancy and accounts for 30% to 50% of malignant tumors. Most develop in the duodenum…

Benign tumors of the small intestine are rare. In a series of 22,810 autopsies, the incidence was 0.16%. The neoplasms may be located anywhere in the small bowel. Stromal tumors, or leiomyomas, are more common in the jejunum, and adenomas are more common in the ileum. Both are benign but have significant malignant counterparts or potential. Benign tumors may be single or multiple. Adenomas, neurofibromas, and…

Intussusception is the invagination of a portion of the intestine into the contiguous distal segment of the enteric tube ( Fig. 71.1 ). It usually occurs in infants at 4 to 10 months of age and is associated with acute enteritis, allergic reactions, and conditions that cause hypermotility. In older persons, intussusception is associated with a polyp or malignancy, an enlarged Peyer patch or diverticulum (e.g.,…

Eosinophilic gastroenteritis is a disease in which tissue eosinophilia occurs in a segment of the gastrointestinal (GI) tract and is associated with GI symptoms ( Fig. 70.1 ). Although first described in 1937, with frequent case reports corroborating the syndrome, the following criteria to establish eosinophilic gastroenteritis were not defined until 1990: 1. The patient must have GI symptoms. 2. Eosinophilic infiltration must be demonstrated on…

The terms food allergy and food hypersensitivity are synonymous. Food “allergy” is distinguished from food “intolerance” in that it includes a true allergic, immunologic response ( Fig. 69.1 ). Food intolerances are not immunologic responses. Allergic responses may be acute and may result in anaphylaxis (a rare occurrence) or may be chronic. Open full size image Fig. 69.1 Intestinal Disturbances Resulting From Food Allergy. This diagram…

Short bowel syndrome (SBS) usually occurs when less than 200 cm of small intestine remains after intestinal surgery. Normally the bowel measures 450 to 500 cm (18–20 ft). When an insult occurs to the bowel resulting in surgical removal of major parts, the patient is left with SBS ( Fig. 68.1 ). Although resection of less than 75% of the bowel, leaving larger amounts of the small bowel,…

The small intestinal bacterial overgrowth (SIBO) syndrome may be caused by a disturbance in gastrointestinal (GI) motility, by an alteration in the anatomy of the intestine, or less likely, by a loss of gastric acid secretion. The disturbance usually causes malnutrition and weight loss from malabsorption. In the healthy small bowel, indigenous bacterial flora growth in the jejunum ranges from 10 2 to 10 5 colony-forming…

Whipple disease is a systemic, infectious disease that primarily affects the small intestine and its lymphatic drainage, although it also has many extraintestinal manifestations, comparable to classic celiac disease ( Fig. 66.1 ). George Whipple first described the clinical syndrome in 1907, but it was not until the bacterium that causes the disease, Tropheryma whippeli, was isolated and identified in 1991 and 1992 that full understanding…

Any disease that affects nutrient digestion or small bowel function or that compromises bowel circulation or motility may result in a malabsorption syndrome, which includes systemic vascular, infectious, and neoplastic diseases ( Fig. 65.1 ). This chapter and others in this section discuss common intestinal diseases that cause malabsorption disorders. Open full size image Fig. 65.1 Malabsorption and Celiac Disease: Primary and Secondary Malabsorption. Gluten enteropathy,…

Since the time of Hippocrates, the term diarrhea has been used to designate abnormally frequent passage of loose stools. However, it is a subjective symptom. Patients describe any increased frequency or fluidity to mean diarrhea. It is generally accepted that more than three bowel movements per day represent diarrhea, or a consistency of watery, large-volume liquid, or both. The clinician must obtain an accurate history and…

Lactose intolerance occurs when there is a deficiency of lactase in the brush border of the small intestine. When a person with lactase deficiency ingests lactose, the poorly digested lactose is fermented in the small and large intestines, resulting in abdominal bloating, discomfort, or diarrhea ( Fig. 63.1 ). Open full size image Fig. 63.1 Lactose Intolerance. Lactose, a disaccharide sugar found in milk, is a…

The rapid development of imaging and histopathologic techniques, in conjunction with an altered pattern of disease and treatments late in the 20th century, has changed the “standard” of testing for small bowel function and anatomy. Testing has now become a sophisticated evaluation performed for outpatients in most clinical practices and in detail at university research centers. Evaluation of the patient thought to have small bowel disease…

Irritable bowel syndrome (IBS) is one of a group of functional gastrointestinal (GI) disorders characterized by abdominal discomfort or pain and frequently associated with a change in bowel movements ( Fig. 61.1 ). Worldwide, IBS is the most frequent symptom complex in patients seeking GI consultation. In the United States, it is estimated that more than 3 million office and hospital visits are attributed to this…

Chronic intestinal pseudo-obstruction (CIPO) is a clinical syndrome that mimics the signs and symptoms of intestinal obstruction ( Fig. 60.1 ). In patients with CIPO, no mechanical obstructive lesion is found on evaluation. CIPO is now thought to be a type of dysmotility and may be related to a functional disturbance in the interstitial cells of Cajal. CIPO may be associated with many disorders of the…

Intestinal obstruction occurs when the onward passage of intestinal contents is limited by mechanical abnormalities or a functional disturbance ( Fig. 59.1 ). Peristaltic activity may be abolished by reflexes originating from diseased structures within, or remote from, the abdominal cavity. When obstructive lesions occur, some motility may persist. The obstruction may be partial or complete, and when it occurs with vascular compromise, it may indicate…

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A diverticulum of the small bowel is a “blind” outpocket from the hollow viscus that consists of one or more layers ( Fig. 57.1 ). Incidence at autopsy ranges from 0.2% to 0.6%. Diverticula are less common in distal areas of the small bowel. Their etiology is unknown, but most appear to be acquired and to consist of mucosal and submucosal layers only. Colonic diverticulosis is…

The yolk sac is connected to the primitive tubular gut by the vitelline (omphalomesenteric) duct in early embryonic stages and is normally obliterated about the seventh week of fetal life. Failure of the duct to disappear results in a variety of remnants; the most common presentation is a sacculation, or pouch, attached to the ileum and best known as Meckel diverticulum ( Fig. 56.1 ). Open…

Congenital lesions develop in the gastrointestinal (GI) tract and may cause intestinal obstruction ( Fig. 55.1 ). Almost all presentations are in newborns and necessitate immediate surgery. The most common site of complete obstruction or atresia (congenital absence or closure) is in the ileum. The duodenum is the second most common site. Obstruction may result from atresia, malrotation of the colon, volvulus, meconium ileus, or imperforate…