Diarrhea

Epidemiology


Etiology

Diarrhea is classified by mechanism (secretory, osmotic, inflammatory) or duration (acute <2 wks, persistent 2-4 wks, chronic >4 wks). Stool characteristics and patient history are key to diagnosis.

Feature Non-Inflammatory Diarrhea Inflammatory Diarrhea (Dysentery)
Pathology No mucosal invasion; toxin-mediated Mucosal invasion & destruction
Location Small Bowel Colon
Stool Volume Large Small, frequent
Stool Content Watery Bloody, mucoid (pus)
Fever Usually absent Common
Fecal WBCs Absent Present
Key Symptom Dehydration Tenesmus, severe abd pain
Example Bugs V. cholerae, ETEC, Norovirus, Giardia Shigella, Campylobacter, EHEC, Salmonella

I. Watery Diarrhea: Non-inflammatory

Characterized by large volume, watery stools without blood or pus. Fecal leukocytes are typically absent.

A. Secretory Diarrhea

B. Osmotic Diarrhea

II. Inflammatory/Invasive Diarrhea (Dysentery)

III. Protozoal Diarrhea

IV. Pre-formed Toxin (Rapid Onset Food Poisoning)

Watery diarrhea

Viral

Norovirus (Norwalk) virus Rotaviruses Adenovirus Astrovirus
Genome/structure Positive ss RNA, non-enveloped, Star of David ds RNA (11 segments), non-enveloped, Wheel-like ds DNA, non-enveloped, type 40/41, fibers (penton) Positive ss RNA, non-enveloped
High risk Group settings, e.g., cruise ships Infants Infants, older children, adults Infants, elderly, immunocompromised
Seasonality Occurs year round November-April peak Late fall and winter peak Winter peak
Vaccine No Yes
Prevalence in developed countries has decreased dramatically due to vaccination.
No No

Bloody diarrhea

Pathophysiology


Inflammatory

Noninflammatory

Clinical features



Diagnostics


Treatment

Antidiarrheal agents

Warning

Loperamide should be avoided in patients with suspected invasive diarrhea with inflammatory features, as it reduces intestinal motility, which consequently increases the risk of bacterial colonization and invasion.