Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Associated symptoms, including fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics and vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, weight loss Weight loss Decrease in existing body weight. Bariatric Surgery, and bloody stools are also important to elicit from the history. Most causes of acute diarrhea are infectious Infectious Febrile Infant and do not require additional workup. Since diarrhea is usually a self-limited condition, management is generally supportive. However, chronic diarrhea can require laboratory studies, stool studies, imaging, or procedures to determine the cause. Management ultimately hinges on treating the underlying pathology, though symptomatic and empiric therapies may be utilized under the right circumstances.
Last updated: 1 Mar, 2021
Diarrhea is the passage of ≥ 3 watery or loose stools in 24 hours.
Diarrhea can be classified by the duration of symptoms:
Additionally, diarrhea may be classified based on the underlying etiology and pathophysiology:
Inflammatory/invasive:
Noninflammatory/noninvasive:
Risk factors:
Secretory:
Osmotic:
Malabsorption Malabsorption General term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients. Malabsorption and Maldigestion:
Inflammatory/exudative:
Altered motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility:
Inflammatory/invasive:
Noninflammatory/noninvasive:
Secretory:
Pathogenesis of secretory diarrhea:
Overactivation of ion transport
channels
Channels
The Cell: Cell Membrane can lead to
secretion
Secretion
Coagulation Studies of
electrolytes
Electrolytes
Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions.
Electrolytes and water into the intestinal lumen, resulting in diarrhea.
Ca2+:
calcium
Calcium
A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.
Electrolytes
CaCC: calcium-activated
chloride channels
Chloride Channels
Cell membrane glycoproteins that form channels to selectively pass chloride ions. Nonselective blockers include fenamates; ethacrynic acid; and tamoxifen.
Ion Channel Myopathy
cAMP
cAMP
An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth.
Phosphodiesterase Inhibitors: cyclic
adenosine
Adenosine
A nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.
Class 5 Antiarrhythmic Drugs monophosphate
CFTR:
cystic
Cystic
Fibrocystic Change
fibrosis
Fibrosis
Any pathological condition where fibrous connective tissue invades any organ, usually as a consequence of inflammation or other injury.
Bronchiolitis Obliterans transmembrane conductance regulator
Cl−:
chloride
Chloride
Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.
Electrolytes
K+:
potassium
Potassium
An element in the alkali group of metals with an atomic symbol k, atomic number 19, and atomic weight 39. 10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the water-electrolyte balance.
Hyperkalemia
Na+:
sodium
Sodium
A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23.
Hyponatremia
NKCC:
sodium
Sodium
A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23.
Hyponatremia–
potassium chloride
Potassium chloride
A white crystal or crystalline powder used in buffers; fertilizers; and explosives. It can be used to replenish electrolytes and restore water-electrolyte balance in treating hypokalemia.
Esophagitis cotransporter
Osmotic:
Pathogenesis of
lactase deficiency
Lactase deficiency
Lactose Intolerance (an etiology of osmotic diarrhea):
Lactose is not broken down and remains in the small intestinal lumen, drawing in water and causing osmotic diarrhea. Bacterial fermentation of lactose results in the symptoms of
bloating
Bloating
Constipation, flatulence, and
abdominal pain
Abdominal Pain
Acute Abdomen.
Malabsorption Malabsorption General term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients. Malabsorption and Maldigestion:
Inflammatory/exudative:
Altered motility Motility The motor activity of the gastrointestinal tract. Gastrointestinal Motility: rapid intestinal passage → ↓ time for fluid absorption Absorption Absorption involves the uptake of nutrient molecules and their transfer from the lumen of the GI tract across the enterocytes and into the interstitial space, where they can be taken up in the venous or lymphatic circulation. Digestion and Absorption
The majority of cases are infectious Infectious Febrile Infant in etiology.
Most patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will have self-limiting Self-Limiting Meningitis in Children symptoms and do not require testing.
Indications for stool studies:
Stool analysis:
Supporting laboratory evaluation:
The differential diagnosis of chronic diarrhea is lengthy, and the evaluation will be guided by clinical suspicion from the history and physical exam. Consultation with a gastroenterologist may be needed.
Laboratory studies:
Imaging and procedures:
Supportive care:
Antidiarrheal agents Antidiarrheal agents Antidiarrheal agents include several drug classes, including opioid agonists, somatostatin analogues, adsorbents, and bile acid sequestrants. These medications mainly work through antimotility and/or antisecretory effects. Antidiarrheal Drugs:
Antibiotic therapy:
Evaluation and management of
patients
Patients
Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.
Clinician–Patient Relationship with acute diarrhea:
Based on the history and physical exam, a determination can be made about whether the diarrhea is related to an
infectious
Infectious
Febrile Infant or a
noninfectious
Noninfectious
Febrile Infant etiology (e.g., medications). Most
patients
Patients
Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.
Clinician–Patient Relationship will not require more than supportive care. However, those with indications for further workup may undergo laboratory and stool testing, which can help guide further therapy.
The treatment of chronic diarrhea hinges on diagnosing and treating the underlying etiology.
Symptomatic therapy:
Empiric therapy Empiric Therapy Meningitis in Children:
Melanosis Melanosis Disorders of increased melanin pigmentation that develop without preceding inflammatory disease. Primary Biliary Cholangitis coli, due to laxative Laxative Agents that produce a soft formed stool, and relax and loosen the bowels, typically used over a protracted period, to relieve constipation. Hypokalemia abuse, as seen on colonoscopy Colonoscopy Endoscopic examination, therapy or surgery of the luminal surface of the colon. Colorectal Cancer Screening
Image: “Black pigmentation of colonic mucosa” by University of Sidi Mohammed Ben Abdellah, Faculty of Medicine and Pharmacy, Department of gastroenterology C, Fez, Morocco. License: CC BY 2.0