Diarrhea is defined as abnormally liquid or unformed stool that is produced at high frequency (greater than 200g/day) lasting less than 14 days. This handwritten video lecture will review causes, clinical findings, investigations work and management of diarrhea for medical students taking the USMLE

ETIOLOGY or CAUSES
Infectious is number one cause of diarrhea (90%). Non infectious include medications, toxin ingestion, ischemia.

CLINICAL FINDINGS
Vomiting and diarrhea is associated with Staph aureus, Bacillus Cereus, Norwalk Virus. Watery Diarrhea is assoicated with Clostridium perfringens, ETEC, and viral diarrhea. Inflammatory diarrhea is caused by campylobacter, salmonella, EHEC, shigella. Inflammatory diarrhea is also associated with pain and fever.

Systemic symptoms are reactive arthritis which is associated with slamonella, campylobacter, shigella, yersinia. Reactive arthritis is associated with arthritis, urethritis, conjunctivits.

Hemolytic Uremic Syndrome (HUS) is caused by E Coli (0157:H7) and Shigella. Syptoms are related to hemolysis and uremia.

EVALUATION of Diarrhea.
If mild than no work up is necessary. However, alarm signs require work up. These alarm signs are severe dehydration, bloody stool, Fever greater than 38.5. History of antibiotic use, abdominal pain and immunocompromised patients should get a workup done.

First step in evaluation is to take a thorough history to limit and narrow down the pathogen causing diarrhea.

If travel history focus on Giardia (Russia, Swimming, Mountanous), ETEC, Norovirus (cruise ship).

What type of food have they ate. Meat food poisoning is caused by staph aureus (egg), clostridium perfringens (canned meat), EHEC (hamburgers), Bacillus (Chicken fried rice), Salmonella (eggs and veg), Yersinia (Milk and cheese), Listeria (more comon in pregnant women). Poultry is primarily associated campylobacter. Diarrhea form seafood is associated with vibrio cholera and vibro parahemolyticus.

Patients associated with daycare and get diarrhea there are certain pathogens. Shigella, Rotavirus, Norovirus, Giardia, Cryptosporidium.

Hospital Acquired Diarrhea is primarily associated with clostridium dificile (anti-biotics).

Immunocompromised patients have increased risk of cryptosporidium and isospora.

Pathogens associated with fever and diarrhea suggests invasive pathogens such as salmonella, shigella, campylobacter as well as virus and entamoeba histolytica and clostridium dificile.

Time can also help determine the cause of diarrhea. If vomiting occurs 1-8 hours after heating then a preformed toxin was ingested. This is most commonly associated with bacillus cereus, S. aureus and Clostridium perfringens. If vomtiing occures 8-72 hours then diarrhea is caused by enterotoxin, primarily Vibro cholera, ETEC. 1-8 days are caused by enteroadherent which prevents absorption of food into gut. This is caused by EPEC and EHEC, Giardia and cryptosporidium.

Lab investigation for diarrhea should be focused on details from history. CBC, Hematocrit, and WBC is important.

Stool Studies - fecal leukoctyesfor WBC in stool are positive in salmonella shigella but this is also found in Ulcerative colitis and crohn's disease as they all cause some sort of inflammation. If blood is present then dysentary pathogens such as campylobacter, salmonella, enterhemorrhagic E. Coli, and entamoeba histolytica. Stool culture is not done routinely, unless it is very severe infection. Ova and parasites if there is persistent diarrhea that is not going away, recent travel, daycare, homosexual or AIDS patients. If there is bloody diarrhea but leukocyte negative. Fecal antigen test for Giardia, and Rotovirus. Testing for toxin such as clostridium dificile if there is a history of anti-biotics. Fecal osmolar gap and fecal fat is used in chornic diarrhea, not acute.

TREATMENT
Initial treatment for diarrhea focuses on relieving dehydration with oral rehydration therapy. Use IV if very severe. Gatorade is not optimal, but it is okay.

Empirical anti-Biotics can be given for diarrhea, but it is not always required because most are self-limiting. Sometimes anti-biotics can actually worsen symtoms of diarrhea. Most commonly prescribed is flouroquinolones such as ciprofloxacin, norfloxacin. Clostridium dificile of metronidazole, vancomycin. EHEC should not be given anti-biotic due to release of shiga toxin. Culture and sensitivity can guide the rest of treatment.

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