It is helpful to classify diarrhea into clinical categories, taking into consideration the duration, setting, and sexual preference of the patient. Diarrhea of abrupt onset of less than 2 to 3 weeks’ duration is called acute diarrhea. If the diarrheal illness lasts longer than 3 weeks, it is called chronic diarrhea. If diarrhea occurs in the setting of antibiotic therapy or after a course of antibiotics, antibiotic-associated diarrhea and pseudomembranous colitis due to C. difficile cytotoxin should be considered.
Acute diarrhea. The most common cause of acute diarrhea is infection.
Food poisoning is produced by a preformed bacterial toxin that contaminates the food. Bacterial replication in the host is not necessary for the development of disease. The resultant illness usually has an acute onset and short duration and occurs in small, well-defined epidemics, without evidence of secondary spread.
Diarrhea resulting from multiplication of organisms in the intestine may be divided into inflammatory-invasive versus noninflammatory-noninvasive categories. Most of these types of diarrhea result from ingestion of contaminated food or water after 1 to 2 days of incubation. Animal reservoirs may exist for some common pathogens, including Salmonella, Campylobacter, Yersinia, Giardia, Cryptosporidium, and Vibrio parahaemolyticus. Waterborne disease in which the pathogens are spread from animals or water to humans is caused by Salmonella, Campylobacter, Shigella, Norwalk virus, Giardia, Vibrio cholerae, toxigenic Escherichia coli, and E. coli: H7.
Diarrhea developing in individuals during or just after traveling is commonly infectious. The most likely organisms are enterotoxigenic E. coli, Salmonella, Giardia, and amebae.
|TABLE. CAUSES OF ACUTE DIARRHEA|
|TABLE. CAUSES OF CHRONIC DIARRHEA|
Homosexual individuals are at a higher risk of exposure to infectious agents. In this setting, it is important to consider amebiasis, giardiasis, shigellosis, rectal syphilis, rectal gonorrhea, and lymphogranuloma venereum caused by Chlamydia trachomatis, and herpes simplex infections of the rectum and perianal area. In patients with acquired immunodeficiency syndrome (acquired immunodeficiency syndrome), infectious agents could include cytomegalovirus, Cryptosporidium, and Candida as well as all of the organisms noted in homosexual persons and immunocompetent individuals.
Chronic and recurrent diarrhea. Any diarrheal illness lasting longer than 3 weeks should be clinically investigated.
Infections. Most viral and bacterial diarrheas are self-limiting and abate within 3 weeks. Diarrhea from Campylobacter and Yersinia may last a few months but rarely becomes chronic. Bowel infections with tuberculosis, amebae, and Giardia may become chronic.
Inflammatory bowel disease. Ulcerative colitis and Crohn’s disease may result in diarrhea of varying severity, depending on the extent and degree of bowel involvement. Diarrhea in Crohn’s disease of the small bowel may be compounded by concomitant bile salt and fat malabsorption.
Diseases of the small intestine may cause chronic diarrhea of varying severity. The mechanism of the diarrhea is usually multifactorial and complex. These diseases include:
- Sprue (nontropical, tropical).
- Whipple’s disease.
- Radiation enteritis.
- Bowel resection/bypass.
- Pancreatic insufficiency from chronic pancreatitis and cystic fibrosis may cause severe fat malabsorption, resulting in chronic diarrhea.
Zollinger-Ellison syndrome resulting from a gastrin-secreting tumor causes increased gastric acid output that overwhelms the absorptive capacity of the proximal small intestine, neutralizes the bicarbonate, and inactivates the pancreatic enzymes secreted into the duodenum. The resulting diarrhea is complicated by malabsorption and bile salt – and fatty acid – stimulated colonic secretion.
Postgastrectomy, enterostomy states may result in diarrhea due to decreased mucosal-chyme exposure as well as poor mixing of digestive juices with luminal contents, resulting in malabsorption.
Bacterial overgrowth of the small intestine may occur in patients with diabetes mellitus, scleroderma, amyloidosis, blind loop syndrome, and large and multiple diverticula of the small bowel. Bacterial degradation of carbohydrates, fatty acids, and bile salts results in diarrhea.
Disaccharidase deficiency. Lactase is deficient to a variable degree in many adult populations, especially in blacks, Asians, southern Europeans, and those of Jewish descent. Even small amounts of dairy products may cause intermittent diarrhea in these individuals.
- Diabetes mellitus.
- Adrenal insufficiency.
- Medullary thyroid cancer.
- Hormone-secreting pancreatic tumors.
- Tumors secreting vasoactive intestinal polypeptide.
- Neoplasms. Villous adenoma, colon cancer with obstruction, and fecal impaction may present with diarrhea.
Drugs and laxatives. Surreptitious use of laxatives and drugs should always be considered in the evaluation of chronic diarrhea.
Irritable bowel syndrome is very common and may present with only chronic intermittent diarrhea, constipation, or a combination of both. Most patients also complain of abdominal cramps, gas, belching, and mucous stools.
Incontinence of stool. Anal sphincter dysfunction due to the presence of fissures, fistulas, perianal inflammation, tears from childbirth, anal intercourse or other trauma, diabetic neuropathy, or neuromuscular disease may result in frequent stools, which may be interpreted by the patient as diarrhea.