Priority Topic: Diarrhea

Key Feature 2: In patients with acute diarrhea, use history to establish the possible etiology (ex: infectious contacts, travel, recent antibiotic or other medication use, common eating place for multiple ill patients). 
Skill: Clinical Reasoning
Phase: Hypothesis generation, History

Key Feature 3: In patients with acute diarrhea who have had recent hospitalization or recent antibiotic use, look for clostridium difficile. 
Skill: Clinical Reasoning
Phase: Hypothesis generation

People's bowels are not their friends. It seems like every other patient who comes in to the family doctor's office or the emergency department falls on one end or the other of the diarrhea-constipation dichotomy. While both can be signs of significant disease, they are often usually benign and respond well to simple treatments. Whenever there is a sudden onset of these symptoms, my role as a primary care physician is to try to figure out the underlying reason so that I can devise an appropriate treatment plan. In this post, I will focus on the patient with acute diarrhea (generally more acutely worrisome than constipation because if severe, it can lead to life-threatening dehydration).

My differential diagnosis for acute diarrhea is as follows:

1. Infection
   1. Viruses
   2. Bacteria
   3. Parasites 
2. Drugs or toxins 
3. Ischemic 
4. Inflammatory bowel disease 
5. Metabolic disease (ex: hyperthyroidism) 

You'll notice at the top of the list of diagnostic possibilities is infection, in three different ways. Acute onset of diarrhea is usually infectious in origin. Looking for clues on history can help to stratify a patient's risk for infection, and includes gathering information on:

1. Possibility of exposure to contaminated food or water
2. Exposure to animals
3. Travel
4. Sexual risk factors (ex: receptive anal intercourse, oral-anal transmission)
5. Occupation (ex: daycare worker)
6. Recent antimicrobials or hospitalisation (in the past 3 months)*
7. Immunocompromised status
8. Living in a nursing home
9. Pregnancy

*For patients who have taken antibiotics or who have been hospitalized in the last 3 months prior to the onset of diarrhea, they are at increased risk for acquiring Clostridium difficile diarrhea (aka C. diff). It is important to know that some people are asymptomatic carriers of C diff, which makes a stool culture for C diff not helpful and so it is not done by the lab. The ordering physician who suspects C diff diarrhea must instead specify that they wish to perform a C diff assay, which tests for the C diff toxins that are produced when C diff is the reason for the diarrhea. On weird but interesting note, one of the most effective treatments for recurrent C diff is fecal microbial transplantation. See the video below as produced by John Hopkins University School of Medicine for more information about this.