Chapter 38: Alterations of Digestive Function

Motility disorders disrupt the normal coordinated movement and transit of food through the gastrointestinal tract; dysphagia represents difficulty initiating or completing swallowing due to neurological or mechanical causes, while gastroesophageal reflux disease results from incompetence of the lower esophageal sphincter allowing retrograde movement of gastric contents into the esophagus, frequently causing secondary inflammation. Hiatal hernia predisposes to reflux symptoms, and obstruction at the pylorus or within the small intestine impairs gastric emptying or intestinal transit, triggering distention, pain, and metabolic consequences. Gastric pathology includes acute and chronic gastritis from caustic injury, nonsteroidal anti-inflammatory drugs, or Helicobacter pylori colonization, along with peptic ulcer disease affecting the duodenum or stomach proper. Malabsorption syndromes arise from pancreatic exocrine insufficiency, disaccharidase deficiency, impaired bile salt circulation, or mucosal damage as in celiac disease, producing steatorrhea and nutritional depletion. Inflammatory bowel diseases present distinct pathological patterns: ulcerative colitis involves continuous mucosal ulceration of the colon with bloody diarrhea and malignancy risk, whereas Crohn disease exhibits skip lesions and transmural inflammation throughout the tract, predisposing to strictures and fistula formation. Irritable bowel syndrome represents a functional disorder without structural pathology characterized by altered motility and visceral hypersensitivity. Diverticular disease involves outpouching of the colon wall, with diverticulitis causing localized inflammation, fever, and abdominal pain. Acute appendicitis typically results from luminal obstruction and requires surgical intervention. Mesenteric ischemia develops from compromised blood flow to intestinal tissue, potentially causing necrosis. Hepatic disorders encompass portal hypertension producing collateral vessel dilation and ascites, jaundice from hyperbilirubinemia, viral and autoimmune hepatitis with inflammatory necrosis, and cirrhosis characterized by irreversible fibrosis and nodular regeneration. Gallbladder disease includes cholelithiasis from cholesterol or pigment precipitation and cholecystitis from stone-induced inflammation. Pancreatic pathology ranges from acute pancreatitis involving enzymatic autodigestion with systemic complications to chronic pancreatitis with progressive loss of exocrine and endocrine function, and pancreatic adenocarcinoma with poor prognosis. The chapter addresses age-related considerations, including congenital malformations and necrotizing enterocolitis in infants and reduced motility with increased malignancy risk in older adults.