Key Feature 5: Pursue investigation, in a timely manner, of elderly with unexplained diarrhea, as they are more likely to have pathology.
Skill: Clinical Reasoning, Selectivity
Phase: Hypothesis generation, Investigation
When someone comes in with a complaint of acute diarrhea, it's usually a viral gastroenteritis. So we don't necessarily do any tests right away if the patient looks well and doesn't have risk factors. That being said, if a patient appears unwell or with risk factors for more serious underlying disease, doing some investigations sooner rather than later is warranted. What are the indications for performing investigations in the setting of acute diarrhea?
If a patient appears dehydrated then ordering a set of electrolytes and a creatinine would be useful to look for complications of the diarrhea, regardless of the etiology. A CBCd may be ordered as a nonspecific marker of disease severity if this is something that may be monitored, say in a patient who is being admitted.
Indications for first-line microbiological testing to look for an underlying infectious pathogen for the diarrhea include:
Imaging would seldom be indicated in the setting of acute diarrhea, but there are 2 reasons for which you may consider getting an imaging study:
*Note that if there is bloody diarrhea, the patient is at risk of having EHEC (Enterohemorrhagic E. coli), and further tests are indicated right off the bat that include: stool culture for EHEC and shiga toxin, and fecal leukocytes or fecal lactoferrin (not available everywhere). Furthermore, if there are ever any pathogens that you are particularly suspicious of, it is a good idea to check with the lab that you are sending the sample to, to see if they test the stool for the bacteria you are suspecting, and it doesn't hurt to write this down on the requisition form as well, as certain organisms are tested for with special techniques, which the lab may not do by default.