Diarrhea: Clinical

Diarrhea is defined as having more than 3 liquidy stools in 24 hours or having a stool weight of over 200 grams per day, but nobody measures stool weight since that can get messy - especially if you’re having diarrhea!

Diarrhea is also classified as acute if it lasts for less than 2 weeks, persistent if it lasts for 2 to 4 weeks, and chronic if it lasts for more than a month.

Diarrhea can also be classified as either inflammatory or non-inflammatory.

Inflammatory diarrhea causes inflammation of the gastrointestinal epithelium and this usually happens with invasive pathogens or as a result of a chronic inflammatory bowel disease, and usually there are systemic symptoms like fever.

In contrast, non-inflammatory diarrhea can be either secretory or osmotic, and neither one usually causes systemic symptoms like fever.

With secretory diarrhea, there’s increased water and electrolyte secretion and decreased absorption.

With osmotic diarrhea, some of the ingested nutrients aren’t fully absorbed, and they remain in the intestinal lumen and pull in water through the process of osmosis!

Now, most cases of acute diarrhea are caused by pathogens, mostly viruses, but also bacteria, protozoa, and parasites that mostly spread through fecal-oral transmission.

The minority of cases of acute diarrhea are due to non-infectious causes like stress, medications, or a toxic ingestion.

Most people with acute diarrhea don’t need to come to the hospital, because symptoms aren’t severe and resolve within 2 weeks. But in terms of figuring out the cause, it’s helpful to ask the right questions - like playing Sherlock Holmes.

With infectious organisms, diarrhea is non-inflammatory and secretory, stools are watery and usually associated with vomiting and this is mostly caused by viruses, such as norovirus and rotavirus.

Watery diarrhea can also be related to the ingestion of contaminated food - food poisoning - and in this case timing offers a clue. If diarrhea occurs within six hours of the ingestion, then the culprit may be Staphylococcus aureus or Bacillus cereus, if diarrhea occurs 8 to 16 hours after the ingestion, then the culprit may be Clostridium perfringens, and if diarrhea occurs more than 16 hours after the ingestion, then the culprit may be enterotoxigenic E. coli.