Acute and Chronic Diarrhea: A Brief Review

Diarrhea diarrhea November 12, 2019

By Steven G. Desautels, MD

Diarrheal diseases represent one of the five leading causes of death worldwide and are a particular concern for children younger than five years old in resource-limited settings.

Diarrhea may be defined as the passage of loose or watery stools, typically at least three times in a 24-hour period. Objectively, it is defined as stool weight exceeding greater than 200 grams per day. It reflects increased water content of the stool, whether due to impaired water absorption and/or active water secretion by the bowel.2Normally, the small intestine and colon absorb 99% of both oral intake and endogenous secretions from the salivary glands, stomach, liver, and pancreas. This constitutes a total fluid load of roughly 9 to 10  liters daily. Of the 10 liters of fluid that enters the jejunum (small intestine) daily (2 liters from food and drink and 8 liters from salivary, gastric, biliary, and pancreatic secretions), the majority is absorbed before entering the colon. Approximately one liter enters the colon with 80-100 ml excreted daily.  Diarrhea results when a disruption of this normally fine-tuned mechanism. A reduction of water absorption by as little as 1% can result in diarrhea.3

The following definitions have been suggested according to the duration of symptoms:

  • Acute – 14 days or fewer in duration
  • Persistent diarrhea – more than 14 but fewer than 30 days in duration
  • Chronic – more than 30 days in duration

Globally, diarrhea kills 2,195 children every day, more than AIDS, malaria, and measles combined.

Diarrheal diseases account for 1 in 9 child deaths worldwide, making diarrhea the second leading cause

of death among children under the age of 5. 2


Approximately 179 million cases of acute diarrhea occur each year in the United States.4  Taken together, most cases of acute infectious diarrhea are likely viral. Among those with severe diarrhea, however, bacterial causes are responsible for most cases. Protozoa are less commonly identified as the etiologic agents of acute gastrointestinal illness. Noninfectious etiologies become more common as the course of the diarrhea persists and becomes chronic.

Infectious causes of acute diarrhea


Norovirus, Rotavirus, Astrovirus


Salmonella, Campylobacter, Shigella, C. diff, E. coli


Cryptosporidium, Giardia, Cyclospora, Entamoeba

Noninfectious causes of acute diarrhea


Antibiotics, antacids, antihypertensives, NSAIDS, antidepressants


Organophosphate insecticides

Ischemic colitis

Fecal impaction

Most episodes of acute diarrhea are mild and self-limited, however, further evaluation should be pursued if any of the following apply:

  • Profuse diarrhea with dehydration
  • Bloody stool
  • Fever >38.5 (101.3)
  • Duration > 48 hours without improvement
  • Recent antibiotic use
  • Community outbreaks
  • Immunocompromised patients
  • Abdominal pain in patients >50
  • Elderly


Chronic diarrhea affects approximately 3 to 5% of the US population at any given time..  A much more extensive differential diagnosis exist for chronic vs acute diarrhea. The principal causes of chronic diarrhea vary based upon the socioeconomic status of the population. In resource-rich settings, irritable bowel syndrome, inflammatory bowel disease, and malabsorption syndromes (e.g., lactose intolerance and celiac disease). Whereas, in resource-limited settings, chronic bacterial, mycobacterial, and parasitic infections or more prominent. However,  functional disorders, malabsorption, and inflammatory bowel disease are also prevalent. Characterizing the diarrhea as infectious, inflammatory, osmotic, or secretory is a useful way to guide evaluation and subsequently elucidating a diagnosis by focused testing. The distinction between types of diarrhea can often be made based upon the medical history but in other cases may require additional laboratory, radiographic and endoscopic evaluation.


Differential diagnosis of chronic diarrhea
Watery diarrhea
A. Osmotic:
Medications Osmotic laxatives (Mg, SO4, PO4)
Unabsorbed sugars Diet foods/drinks/gum (sorbitol); enzyme deficiencies (lactase/sucrase)
Medications Stimulant laxatives, antibiotics, many others
Small intestinal bacterial overgrowth
Tumors Carcinoid, gastronome, medullary thyroid cancer, VIPoma
Systemic Adrenal insufficiency, hyperthyroidism
Bile salt malabsorption Postcholecystectomy, Ileal resection
Non-invasive infections Giardia, Cryptosporidium
Fatty diarrhea
A. Maldigestion Decreased duodenal bile salt concentration (bile duct obstruction, ileal resection).  Pancreatic dysfunction
B. Malabsorption Mucosal disease (celiac sprue, giardiasis, Whipple’s disease)
Inflammatory diarrhea
A. Inflammatory bowel disease Crohn’s, Ulcerative Colitis
B. Malignancy Colon cancer, lymphoma
C. Radiation colitis/enteritis
D. Mastocytosis
E. Infections C. difficle, CMV, Entamoeba
F. Ischemia


If you are suffering with ongoing diarrhea, please contact one of our specialists at Granite Peaks Gastroenterology in Sandy or Lehi.