Summary for Chapter 24 – Lower Gastrointestinal Disorders
The most common intestinal symptoms include constipation, intestinal gas, and diarrhea. Constipation accompanies a wide range of conditions but generally correlates with low-fiber diets, low food intake, and physical inactivity. Intestinal gas is largely produced by bacteria that colonize the colon and is often associated with nutrient malabsorption. Diarrhea can result from intestinal infections, malabsorption, and motility disorders and may require oral rehydration therapy to replace fluid and electrolyte losses. Dietary modifications may help to improve bowel function and intestinal discomfort.
Malabsorption syndromes can be caused by reduced digestive secretions or damaged intestinal mucosa. Malabsorption usually affects multiple nutrients and causes complications that impair nutritional status further. Fat malabsorption, usually indicated by the development of steatorrhea, is associated with the loss of food energy and deficiencies of essential fatty acids, fat-soluble vitamins, and some minerals. Bacterial overgrowth can result from impaired peristalsis or reduced gastric acidity and typically causes malabsorption of fat and vitamin B12.
Chronic pancreatic disorders can lead to widespread maldigestion and malabsorption due to impaired digestive secretions. Acute pancreatitis is short-lived and does not cause permanent damage, but requires that food and liquids be withheld until healing has occurred. Chronic pancreatitis, most often caused by alcohol abuse, results in digestive enzyme deficiencies and requires pancreatic enzyme replacement therapy. Cystic fibrosis, a genetic disorder associated with thickened exocrine secretions, causes obstructive lung disease and pancreatic damage. Children have high protein and energy requirements and must use pancreatic enzymes and dietary supplements to reverse malnutrition.
Disorders of the small intestine that cause damage to mucosal tissue, such as celiac disease and Crohn’s disease, often result in malabsorption. Although a gluten-free diet can alleviate the symptoms of celiac disease, there is no cure for Crohn’s disease and intestinal resection is often necessary. Ulcerative colitis is an inflammatory condition that affects the colon only, and severe cases can be cured by colectomy. Short bowel syndrome is a frequent consequence of major resections of the small intestine and may require permanent parenteral nutrition support. In many patients, intestinal adaptation may improve absorptive capacity after surgical resections.
Irritable bowel syndrome and diverticular disease are common disorders affecting the colon. Irritable bowel syndrome is characterized by abdominal pain and alternating diarrhea and constipation. Although the causes are unknown, it is influenced by stress and psychological factors. Diverticulosis is often asymptomatic until complications develop; its prevalence increases with advancing age and may be related to low fiber intakes. Individuals with both irritable bowel syndrome and diverticulosis may benefit from a high-fiber diet.
Colostomies and ileostomies are surgically created openings in the abdominal wall using the colon or ileum. Fluid and electrolyte requirements are greater after an ostomy because colon function is reduced or absent. Foods that are poorly digested may cause obstructions in people with ostomies, although thorough chewing can reduce risk. Foods should be avoided if they provoke diarrhea or cause excessive gas or strong odors.