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Acute Diarrhea

Acute diarrhea is defined as diarrheal disease of rapid onset, often with nausea, vomiting, fever, or abdominal pain. Most episodes of acute gastroenteritis will resolve within 3 to 7 days.

Clinical Evaluation of Acute Diarrhea

The nature of onset, duration, frequency, and timing of the diarrheal episodes should be assessed. The appearance of the stool, buoyancy, presence of blood or mucus, vomiting, or pain should be determined.

Contact with a potential source of infectious diarrhea has occurred.

Drugs that may cause diarrhea include laxatives, magnesium-containing compounds, sulfa-drugs, antibiotics.

Physical Examination

Assessment of Volume Status. Dehydration is suggested by dry mucous membranes, orthostatic hypotension, tachycardia, mental status changes, and acute weight loss.

Abdominal tenderness, mild distention and hyperactive bowel sounds are common in acute infectious diarrhea. However, the presence of peritoneal signs or rigidity suggests toxic megacolon or perforation, requiring radiologic examination of the abdomen.

Evidence of systemic atherosclerosis suggests ischemia. Lower extremity edema suggests malabsorption or protein loss.

Acute Infectious Diarrhea

Infectious diarrhea is usually classified as noninflammatory or inflammatory, depending on whether the infectious organism has invaded diarrhea

Noninflammatory infectious diarrhea is caused by organisms that produce a toxin (enterotoxigenic E coli strains, Vibrio cholerae).

Blood or mucus in the stool suggests inflammatory disease, usually caused by bacterial invasion of the mucosa (enteroinvasive E coli, Shigella, Salmonella, Campylobacter). 

Vomiting out of proportion to diarrhea is usually related to a neuroenterotoxin-mediated food poisoning from Staphylococcus aureus or Bacillus cereus, or from an enteric virus, such as rotavirus (in an infant), or a small round virus.

Traveler's diarrhea is a common type of acute infectious diarrhea. Typically, three or four unformed stools are passed per 24 hours, usually starting on the third day of travel and lasting 2-3 days. Accompanying symptoms may include anorexia, nausea, vomiting, abdominal cramps, abdominal bloating, and flatulence.

Antibiotic-Related Diarrhea

Diarrhea ranges from mild illness to life-threatening pseudomembranous colitis. Overgrowth of Clostridium difficile causes pseudomembranous colitis. Amoxicillin, cephalosporins and clindamycin have been implicated most often, but almost any antibiotic can be the cause.

Patients with pseudomembranous colitis have high fever, cramping, leukocytosis, and severe, watery diarrhea.

Latex agglutination testing for C difficile toxin can provide results in 30 minutes.

Enterotoxigenic E Coli

IV. Diagnostic Approach to Acute Infectious Diarrhea

A. An attempt should be made to obtain a pathologic diagnosis in patients who give a history of recent ingestion of seafood (Vibrio parahaemolyticus), travel or camping, antibiotic use, homosexual activity, or who complain of fever and abdominal pain.

B. Blood or mucus in the stools indicates the presence of Shigella, Salmonella, Campylobacter jejuni, enteroinvasive E. coli, C. difficile, or, less likely, Yersinia enterocolitica.

C. Most cases of mild diarrheal disease do not require laboratory studies to determine the etiology. In moderate to severe diarrhea with fever or pus in stools, a liquid stool culture for bacterial pathogens (Salmonella, Shigella, Campylobacter) is submitted. If antibiotics were used recently, stool should be sent for Clostridium difficile toxin.

V. Laboratory Tests and Procedures for Acute Diarrhea

A. Fecal leukocytes is a screening test which should be obtained if moderate to severe diarrhea is present. Numerous leukocytes indicate Shigella, Salmonella, or Campylobacter jejuni.

B. Stool cultures for bacterial pathogens should be obtained if high fevers, severe or persistent (>14 d) diarrhea, bloody stools, or leukocytes are present.

C. Examination for ova and parasites is indicated for persistent diarrhea (>14 d), travel to a high-risk region, gay males, infants in day care, or dysentery.

D. Blood cultures should be obtained prior to starting antibiotics if severe diarrhea and high fever is present.

E. E coli 0157:H7 Cultures. Enterotoxigenic E coli should be suspected if there are bloody stools with minimal fever, or when diarrhea.