Diarrhea, Acute and Chronic

Incidence in USA: 200–300 million new cases/y of acute, with >900,000 hospital admissions

Chronic: 1–5% of population; increasing with age; female at greater risk than male

Acute: Male and female equivalent

Hypovolemia with hemodynamic instability

Electrolyte abnormalities, especially hypokalemia

Acid-base abnormalities: May be non–anion gap acidosis or alkalosis, depending on underlying cause

Chronic

• Underlying disease, especially iatrogenic (e.g., infection with antibiotic-induced diarrhea, end-stage liver disease with lactulose-induced diarrhea, or disaccharide [usually lactose] intolerance)

• Hormone-producing tumors (e.g., carcinoid, VIPomas, gastrinomas)

• Vitamin K malabsorption with coagulopathy

• Extraintestinal manifestations of IBD (e.g., deforming arthritis, cholangitis)

• Stress-steroid therapy in IBD

• Psychologic symptoms in up to 50% of pts with IBS; often alternates with constipation

• Postsurgical losses that may drain via ileostomy or fistula or may be due to inadequate bowel absorption secondary to resection (short bowel syndrome)

Acute

Viral, bacterial, or protozoan disease

Acute: Abrupt onset of loose stools in healthy individual: Viral—Self-limited, 1–3 d, causing changes in small intestinal cells with a shortened transit time; bacterial—Tends to occur in groups of individuals (if within 12 h of a meal, usually due to preformed toxin); protozoan—Prolonged watery diarrhea from contaminated water supply in endemic area.

Chronic: Too-frequent passage of stools that are too loose for too long; >200 g/day of stool for >4 wk.

Multifactorial medical problem that requires supportive therapy and attention to the underlying etiology.

Only one in a spectrum of medical problems associated with an underlying disease or with treatment of disease. Supportive therapy includes fluid and lyte repletion and attention to acid-base balance.

Toxic megacolon: Extreme manifestation of inflammatory or infectious bowel disease is a surgical emergency. Pts often septic.

Chronic:

• Osmotic: Laxatives, indigestible carbohydrates

• Secretory: Hormone-producing tumors

• Exudative: IBD, pseudomembranous colitis

• Decreased mucosal contact/mixing: Short bowel syndrome, IBS, hypermotility secondary to vagotomy, diabetic neuropathy

• Malabsorption: Pancreatic exocrine insufficiency, celiac disease, Whipple disease, small-bowel bacterial overgrowth

Acute

• Viral or bacterial (with or without toxin) or protozoan (see Overview )