(Last Updated On: March 8, 2016)diarrhea meme

Chapter 5 – “Diarrhea”

Welcome to the fifth installment of “Inconceivable: medical terms that don’t mean what you think they mean.”

Your patient has had 24 hours of vomiting and abdominal cramping. He tells you that he became concerned when in addition to the vomiting he began to have diarrhea, which he describes as a single liquid stool without blood. Does your patient actually have diarrhea?

All loose stools are not diarrhea. Diarrhea is both a decrease of the consistency of stool and three or more bowel movements in a day. Your patient must have a change in both the consistency and frequency of his or her stool. Acute diarrhea lasts between 1 and 14 days, after which it is defined as persistent diarrhea. Some sources further specify diarrhea lasting longer than 30 days as chronic diarrhea.

A common question that arises in the ED is whether or not to obtain stool studies. With regards to stool testing, there are some things to consider. Stool culture routinely tests for only Campylobacter, Shigella, Salmonella, Aeromonas, and Yersinia, and only about 2% of stool cultures are positive. Stool studies are expensive and labor intensive, so only test if you anticipate it will change management.

Scenarios in which to consider studies in immunocompetent patients:

  • Send for ova and parasite (O and P) if your patient has risk factors for parasitic infection
  • Send for C. difficile if your patient has liquid stool and risk factors for C. diff (recent antibiotics or health care exposure)
  • Send for culture if patient has had >14 days  or has fever and >48 hours duration of illness
  • Send for culture if patient is a nursing home resident, works in food service, or if he/she works in a day-care
  • Test patient for HIV if at risk and/or having recurrent bouts without other explanation

In general, empiric antibiotic treatment for presumed infectious diarrhea is not recommended as most diarrheal illnesses are viral and in fact approximately 50% are caused by noroviruses. Additionally, even most bacterial etiologies of diarrhea are self-limiting, and antibiotics can cause serious problems in certain situations. For example, antibiosis of salmonella-induced diarrhea can lead to a prolonged carrier-state putting more patients at risk, and empiric antibiotics may induce resistance in a patient’s enteric bacteria.

There are three scenarios in which empiric treatment is recommended, however:

  • Traveler’s diarrhea  – without fever or bloody diarrhea treat with ciprofloxacin 500mg q12h x 3 day
  • Traveler’s diarrhea with fever or blood – azithromycin 1g x1
  • Suspected Giardia – diarrhea lasting >10 days with history of fresh water ingestion should be treated with metronidazole 250mg q8h x 7 days

When treating diarrhea in the emergency department, antimotility agents such as loperamide are safe except in patients with bloody diarrhea because of the risk of infection with shiga-toxin-producing E. coli or those at risk for C. diff.

Finally, remember that all diarrhea is not infectious. Other etiologies such as medication side effects, inflammatory bowel disease, ischemic colitis, or partial bowel obstruction must always be considered.

So to summarize, diarrhea is both:

a) A decrease of the consistency of stool, AND

b) Three or more bowel movements in a day

Your patient must have a change in both the consistency and frequency of his or her stool if you are to correctly label them with this entity.


DuPont HL. Acute infectious diarrhea in immunocompetent adults. N Engl J Med. 2014 Apr 17;370(16):1532-40. doi: 10.1056/NEJMra1301069.

Richard LG, et al. Practice Guidelines for the Management of Infectious Diarrhea. IDSA Guidelines, CID 2001:32 (1 February)




Dr. Krueger is currently an attending physician at Advocate Lutheran General Hospital and a former UIC EM Chief Resident.