Diarrhea can be classified in two ways: according to the length of time that the condition lasts or the possible cause or setting of the disease.1
Diarrhea Is Generally Classified Based on Duration
If the symptoms come on suddenly but clear up in less than two weeks, it is called acute diarrhea.2 In the U.S., this type of diarrhea is one of the most common illnesses3 and, worldwide, it is among the leading causes of death in children younger than 5 years old.4 Acute diarrhea is typically caused by bacteria, viruses or parasites.5
Persistent diarrhea is when the illness lasts from two to four weeks,6 and can be triggered by parasites, bacteria or viruses.7 If the condition lasts longer than four weeks, it is considered chronic diarrhea.8 Although often caused by digestive disorders, chronic diarrhea can also occur due to other factors, such as:9
• Excessively consuming high amounts of alcohol, caffeine, sugar or dairy
• Taking certain medications
• Surgical procedure
Types of Diarrhea According to Pathophysiology
Diarrhea may also be classified according to the mechanism that the condition undertakes, although there may be an overlap between them:
• Osmotic diarrhea — This form of diarrhea involves the retention of water in the bowel, which results from the accumulation of nonabsorbable substances. For instance, sugar substitutes like sorbitol and mannitol can slow down absorption while causing rapid motility of the small intestine.10
• Secretory diarrhea — When electrolyte absorption is affected, the body releases water into the small intestine, causing loose bowel movements.11 This type of diarrhea is often a result of infection or the intake of certain drugs.12
• Motility-related diarrhea — Hypermotility, or the quick movement of food through the intestines, is a precursor for this type of diarrhea. Motility-related diarrhea occurs when the body lacks time to absorb nutrients and water due to conditions like diabetic neuropathy or hyperthyroidism, or when a person undergoes a surgery called a vagotomy.13
• Inflammatory diarrhea — This occurs when certain pathogens like shigella, salmonella, campylobacter, E. coli or Clostridium difficile attack your intestinal cells. Inflammatory diarrhea mainly affects the colon, causing abdominal pain, fever and even bloody diarrhea. This is common in people with ulcerative colitis and Crohn’s disease.14
You should remember that diarrhea can cause dehydration and may prevent your body from carrying out important functions.15 This can eventually lead to severe problems, such as seizures, urinary problems, heat injuries, kidney failure or hypovolemic shock,16 and can even be fatal.17 However, with prompt and appropriate treatment, these complications can be avoided.18
Other Types of Diarrhea You Can Be Affected With
Aside from the aforementioned conditions, take note of these types of diarrhea that can harm you or someone you know:
• Explosive diarrhea — Watery diarrhea is expelled violently, along with gas. Bacterial infections are the common culprits of this type of diarrhea.19
• Traveler’s diarrhea — This disorder occurs when a patient consumes contaminated food or water. Common indicators of traveler’s diarrhea, aside from loose bowels, include abdominal cramps, nausea, vomiting and fever.20
• Chronic oily or fatty diarrhea — Patients with oily or fatty diarrhea expel greasy or very bad-smelling stools. This type of diarrhea mainly arises after a patient eats fat-, fiber- or potassium oxalate-rich foods, nuts, oily and fatty fish, artificial fats or alcohol, although some diseases, such as liver or kidney damage or failure, Crohn’s disease, celiac disease or gallstones may trigger oily or fatty diarrhea, too.21
• Burning diarrhea — As its name implies, this type of diarrhea causes a painful and burning sensation while passing stools. Burning diarrhea typically develops after eating spicy foods, since a compound present in chilies called capsaicin may disrupt digestive tissue function. The burning feeling arises because the capsaicin is not broken down properly before it leaves the body. Other possible causes of burning diarrhea include:22
◦ Failure to break down stomach acids, digestive enzymes and bile
◦ Eating large, rough and seed-containing foods that may damage rectal tissues
◦ Physical trauma such as increased wiping of the buttocks when passing stoolt
• Laxative abuse
• Foamy diarrhea — Foamy diarrhea may occur among people with celiac disease, but this condition may also indicate IBS, a parasitic infection or pancreatitis. In some cases, foamy stools or diarrhea may occur after abdominal surgeries, particularly those that involve removing a section of your small or large intestine.23
If you notice that your stools have different colors, they may be due to certain factors:24,25,26
Dark or black/tarry stools — These may result from upper gastrointestinal tract bleeding caused by ulcers, noncancerous tumors or acid reflux-caused bleeding esophagus sores.
Foods like black licorice and blueberries, as well as iron supplements, may cause black stools, too.
Green stools — Consuming leafy green vegetables, green food coloring, iron-rich foods and supplements,27 or presence of bacteria strains or parasites can cause green stools.28
Orange stools — Yellow or orange food coloring and foods like carrots, cilantro, collard greens, thyme and kale can lead to orange stools.
Lack of bile or improper bile absorption due to conditions like diarrhea, short bowel syndrome (SBS) or irritable bowel syndrome (IBS) can also cause this.29
Red stools — These can be due to lower intestinal tract bleeding caused by hemorrhoids, colitis, polyps in the colon or noncancerous tumors.
Dietary factors include ingesting red food coloring, beets, cranberries or tomato juice or soup.
White stools — Lack of bile, which may signal a blocked bile duct can turn stools white. Taking antacids and anti-diarrhea medicines are also possible causes.
Yellow stools — Increased amounts of fat in stool turn stools yellow. This occurs because of a malabsorption disorder like celiac disease and cystic fibrosis, Giardia disorder or Gilbert’s syndrome.
Gray stools — Hepatitis, gallbladder disorders or malabsorption diseases are possible causes.