Diarrhea E Rahimi, MD Assiatant Professor Department Of Internal Medicine MUK

DEFINITION Diarrhea and constipation are exceedingly common and ， together ， exact an enormous toll in terms of mortality ， morbidity ， social inconvenience ， loss of work productivity ， and consumption of medical resources. W orldwide ， > 1 billion individuals suffer one or more episodes of acute diarrhea each year.

DEFINITION Among the 100 million persons affected annually by acute diarrhea in the United States ， nearly half must restrict activities, 10% consult physicians, require hospitalization ， and die (primarily the elderly). The annual economic burden to society may exceed $20 billion. Acute infectious diarrhea remains one of the most common causes of mortality in developing countries ， particularly among impoverished infants ， accounting for 1.8 million deaths per year.

INTESTINAL FLUID ABSORPTION AND SECRETION On an average day, 9 L of fluid enter the (GI) tract, - 1 L of residual fluid reaches the colon ， and the stool excretion of fluid constitutes about 0.2 L/d. The colon has a large capacitance and functional reserve and may recover up to four times its usual volume of 0.8 L/d, provided the rate of flow permits reabsorption to occur. Thus, the colon can partially compensate for excess fluid delivery to the colon that may result from intestinal absorptive or secretory disorders.

Diarrhea is loosely defined as passage of abnormally liquid or unformed stools at an increased frequency. For adults on a typical Western diet ， stool weight >200 g/d can generally be considered diarrheal. Diarrhea may be further defined as acute if 4 weeks in duration DEFINITION

Two common conditions ， usually associated with the passage of stool totaling <200. Pseudodiarrhea ， or the frequent passage of small volumes of stool ， is often associated with rectal urgency ， tenesmus ， or a feeling of incomplete evacuation ， and accompanies IBS or proctitis. Fecal incontinence is the involuntary discharge of rectal contents and is most 0fen caused by neuromuscular disorders or structural anorectal problems. DEFINITION

Diarrhea and urgency ， especially if severe ， may aggravate or cause incontinence. Pseudodiarrhea and fecal incontinence occur at prevalence rates comparable to or higher than that of chronic diarrhea and should always be considered in patients complaining of "diarrhea." Overflow diarrhea may occur in nursing home patients due to fecal impaction that is readily detectable by rectal examination. A careful history and physical examination generally allow these conditions to be iscriminated from true diarrhea. DEFINITION

More than 90% of cases of acute diarrhea are caused by infectious agents; these cases are often accompanied by vomiting ， fever ， and abdominal pain. The remaining 10% or so are caused by medications ， toxic ingestions ， ischemia ， food indiscretions ， and other conditions. Acute Diarrhia

Most infectious diarrheas are acquired by fecal oral transmission or ， more commonly ， via ingestion of food or water contaminated with pathogens from human or animal feces. In the immunocompetent person ， the resident fecal microflora ， containing >500 taxonomically distinct species ， are rarely the source of diar Acute Diarrhia

1. Travelers Nearly 40% of tourists to endemic regions of Latin America ， Afica ， and Asia develop so- called trave1er's diarrhea. Most common1y due to enterotoxigenic or enteroaggregative Escherichia coli as well as to Campylobacter ， Shigella ， Aeromonas ， norovirus ， Coronavirus ， and Salmonella. Visitors to Russia (especially St. Petersburg) may have increased risk of Giardia-associated diarrhea. Acute Diarrhia: 5 high risk groups

Travelers visitors to Nepal may acquire Cyclospora. Campers ， back packers ， and swimmers in wilderness areas may become infected with Giardia. Cruise ships may be affected by outbreaks of gastroenteritis caused by agents such as norovirus. Acute Diarrhia: 5 high risk groups

2. Consumers of certain foods. Diarrhea close1y following food consumption at: a picnic ， banquet ， or restaurant may suggest infection with Salmonella Campylobacter ， or Shigella from chicken enterohemorrhagic E. coli (01 57:H7) from undercooked hamburger Bacillus cereus from fried rice or other reheated food Staphylococcus aureus or Salmonella from mayonnaise or creams Acute Diarrhia: 5 high risk groups

2. Consumers of certain foods. Salmonella from eggs Listeria from uncooked foods or soft cheeses Vibrio species ， Salmonella ， or acute hepatitis A from seafood ， especially if raw. Acute Diarrhia: 5 high risk groups

3. Immunodeficient persons. primary immunodeficiency (e.g. ， IgA deficiency ， common variab1e hypogammag1obulinemia ， chronic granu1omatous disease) secondary immunodeficiency states Common enteric pathogens: Mycobacterium species cytomegalovirus Adenovirus herpes simplex Acute Diarrhia: 5 high risk groups

3. Immunod φ cient persons. Protozoa Cryptosporidium Isospora belli Microsporida Blastocystis hominis Acute Diarrhia: 5 high risk groups

3. Immunod φ cient persons. In patients with AIDS agents transmitted venereally per rectum (Neisseria onorrhoeae ， Treponema pallidum ， Chlamydia) may contribute to proctocolitis. Persons with hemochromatosis are especially prone to invasive ， even fatal ， enteric infections with Vibrio species and Yersinia infections and should avoid raw fish. Acute Diarrhia: 5 high risk groups

4. Daycare attendees and their family members. Infections with Shigella ， Giardia ， Cryptosporidium ， rotavirus ， and other agents are very common and shou1d be considered. 5. Institutionalized persons. Infectious diarr Acute Diarrhia: 5 high risk groups

5. Institutionalized persons. Infectious diarrhea is one of the most frequent categories of nosocomial infections in many hospita1s and long-term care facilities; the causes are a variety of microorganisms but most common1y C. difficile. C. difficile can affect those with no history of antibiotic use and may be acquired in the community. Acute Diarrhia: 5 high risk groups

Side effects from medications: the most common noninfectious causes of acute diarrhea Antibiotics cardiac antidysrhythmics Antihypertensives nonsteroidal anti-inflammatory drugs (NSAIDs) certain antidepressants chemotherapeutic agents ， Other Causes

Side effects from medications: Bronchodilators Antacids laxatives. Other Causes

Occlusive or nonocclusive ischemic colitis typically occurs in persons >50 years; often presents as acute lower abdominal pain preceding watery ， then bloody diarrhea; and generally results in acute inf1ammatory changes in the sigmoid or left colon while sparing the rectum. Other Causes

colonic diverticulitis graft-versus-host disease. toxins including organophosphate insecticides; amanita and other mushrooms; arsenic preformed environmental toxins in seafood ， such as ciguatera and scombroid. Acute anaphylaxis to food ingestion can have a similar presentation. Conditions causing chronic diarrhea can also be confused with acute diarrhea early in their course. Other Causes

This confusion may occur with inflammatory bowel disease (IBD) andsome of the other inflammatory chronic diarrheas that may have an abrupt rather than insidious onset and exhibit features that mimic infection. Other Causes

The decision to evaluate acute diarrhea depends on its severity and duration and on various host factors. Most episodes of acute diarrhea are mild and self- limited and do not justify the cost and potential morbidity rate of diagnostic or pharmacologic interventions. APPROACH TO THE PATIENT

Indications for evaluation profuse diarrheawith dehydration grossly bloody stools fever 38 duration > 4 8 h without improvement recent antibiotiι use new community outbreaks associated severe abdominal pain in patients >50 years elderly (70 years) immunocompromised APPROACH TO THE PATIENT

Indications for evaluation In some cases of moderately severe febrile diarrhea associated with feιal leukocytes (or inιreased feιal levels of the leukocyte proteins ， such as calprotectin) or with gross blood ， a diagnostic evaluation might be avoided in favor of an empirical antibiotic trial (see below). The cornerstone of diagnosis. APPROACH TO THE PATIENT

Diarrhea lasting >4 weeks warrants evaluation to exclude serious underlying pathology. In contrast to acute diarrhea ， most of the causes of chronic diarrhea are noninfectious. The classification of chronic diarrhea by pathophysiologic mechanism facilitates a rational approach to management ， although many diseases cause diarrhea by more than one mechanism. Chronic Diarrhia

Diarrhea lasting >4 weeks warrants evaluation to exclude serious underlying pathology. In contrast to acute diarrhea ， most of the causes of chronic diarrhea are noninfectious. The classification of chronic diarrhea by pathophysiologic mechanism facilitates a rational approach to management ， although many diseases cause diarrhea by more than one mechanism. Chronic Diarrhia