Diarrhea: Clinical

To be retired ⓘ

00:00 / 00:00



Diarrhea: Clinical

USMLE® Step 2 questions

0 / 25 complete


USMLE® Step 2 style questions USMLE

of complete

A 75-year-old woman comes to the emergency department with worsening shortness of the breath for the past week. She is admitted with a diagnosis of pneumonia. Her condition is managed with observation and intravenous levofloxacin 750 mg daily for 2 weeks. On the 15th day of hospitalization, she has three episodes of diarrhea. The following day, her white blood cell count is 21,000/mm3, and she begins complaining of abdominal pain. Her pulse is 110/min, respirations are 18/min, and blood pressure is 92/50 mm Hg. Physical examination shows she is confused and has diffuse abdominal tenderness without guarding, rebound, or rigidity. Which of the following is the most appropriate response?


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.


Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.