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The main purpose of the gastrointestinal tract is the transport of food and the absorption of nutrients. Many pathologic conditions of the gastrointestinal tract impair either or both of these functions. The gastrointestinal tract, and especially the colon, is a common site of malignancy. The two main symptoms related to pathology of the gastrointestinal tract are abdominal pain and gastrointestinal hemorrhage.
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The differential diagnosis for abdominal pain can be classified as either acute or chronic, based upon the length of time of the pain (Table 14-1). The four categories of the causes of acute abdominal pain are (1) inflammation, including appendicitis, cholecystitis, pancreatitis, and diverticulitis; (2) perforation; (3) obstruction; and (4) vascular disease, including acute ischemia and ruptured abdominal aortic aneurysm. The five categories of causes of chronic abdominal pain are (1) inflammation, including peptic ulcer disease, esophagitis, inflammatory bowel disease, and chronic pancreatitis; (2) vascular disease, including chronic ischemia; (3) metabolic disease, including porphyria; (4) abdominal wall pain; and (5) functional causes, including irritable bowel syndrome. The most frequent causes of chronic abdominal pain are functional.
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The second main symptom of gastrointestinal pathology is bleeding (Table 14-2). The character of the blood can help identify the source: hematemesis (i.e., vomiting of bright red blood), if the source is gastrointestinal, is most likely due to a source proximal to the ligament of Treitz. Melena (i.e., black, tarry stool) is most often due to upper gastrointestinal bleeding. Hematochezia (i.e., bright red blood per rectum) usually indicates a lower gastrointestinal bleed (or very rapid upper gastrointestinal bleed). The differential diagnosis of upper gastrointestinal bleeding includes gastritis, esophageal varices, and peptic ulcer disease (as a result of erosion into a blood vessel). The diagnosis of the source of an upper gastrointestinal bleed is often made by endoscopy. The differential diagnosis of lower gastrointestinal bleeding includes a rapid upper gastrointestinal bleed, diverticulosis, infections (e.g., Salmonella, Shigella), cancer, inflammatory bowel disease, and anal fissures or hemorrhoids. The diagnosis of a lower gastrointestinal bleed is often determined by flexible sigmoidoscopy or colonoscopy.
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This chapter will discuss pediatric gastrointestinal disorders, pathology of the oral cavity and salivary glands ...