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, includingfeverFeverFever 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,nauseaNauseaAn 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 andvomitingVomitingThe forcible expulsion of the contents of the stomach through the mouth.Hypokalemia,weight lossWeight lossDecrease in existing body weight.Bariatric Surgery, and bloody stools are also important to elicit from the history. Most causes of acute diarrhea are infectious 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.
Additionally, diarrhea may be classified based on the underlying etiology and pathophysiology:
Infectious diarrhea:
Inflammatory (invasion by an infectious organism)
Noninflammatory (no invasion of the mucosa by the organism)
Noninfectious diarrhea:
Secretory (efflux ofelectrolytesElectrolytesElectrolytes 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)
Osmotic (water is drawn into the intestinal lumen)
MalabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion (impaired nutrientabsorptionAbsorptionAbsorption 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)
Inflammatory (inflammatory process causing mucosal damage)
ShigellaShigellaShigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir.Shigella
SalmonellaSalmonellaSalmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium).Salmonella
Campylobacter jejuniCampylobacter jejuniA species of bacteria that resemble small tightly coiled spirals. Its organisms are known to cause abortion in sheep and fever and enteritis in man and may be associated with enteric diseases of calves, lambs, and other animals.Campylobacter
Yersinia enterocoliticaYersinia enterocoliticaA species of the genus yersinia, isolated from both man and animal. It is a frequent cause of bacterial gastroenteritis in children.Yersinia spp./Yersiniosis
Escherichia coliEscherichia coliThe gram-negative bacterium Escherichia coli is a key component of the human gut microbiota. Most strains of E. coli are avirulent, but occasionally they escape the GI tract, infecting the urinary tract and other sites. Less common strains of E. coli are able to cause disease within the GI tract, most commonly presenting as abdominal pain and diarrhea.Escherichia coli(enterohemorrhagic and enteroinvasive)
Clostridioides difficile
ListeriaListeriaListeria spp. are motile, flagellated, gram-positive, facultative intracellular bacilli. The major pathogenic species is Listeria monocytogenes. Listeria are part of the normal gastrointestinal flora of domestic mammals and poultry and are transmitted to humans through the ingestion of contaminated food, especially unpasteurized dairy products.Listeria Monocytogenes/Listeriosis monocytogenes
Vibrio parahaemolyticusVibrio parahaemolyticusA species of bacteria found in the marine environment, sea foods, and the feces of patients with acute enteritis.Vibrio
Protozoal:
Entameoba histolytica
Strongyloides
Noninflammatory/noninvasive:
Bacterial:
Staphylococcus aureusStaphylococcus aureusPotentially pathogenic bacteria found in nasal membranes, skin, hair follicles, and perineum of warm-blooded animals. They may cause a wide range of infections and intoxications.Brain Abscess
Clostridium perfringensClostridium perfringensThe most common etiologic agent of gas gangrene. It is differentiable into several distinct types based on the distribution of twelve different toxins.Gas Gangrene
Bacillus cereusBacillus cereusA species of rod-shaped bacteria that is a common soil saprophyte. Its spores are widespread and multiplication has been observed chiefly in foods. Contamination may lead to food poisoning.Bacillus
GiardiaGiardiaA genus of flagellate intestinal eukaryotes parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape.Nitroimidazoles lamblia
CryptosporidiumCryptosporidiumA genus of coccidian parasites of the family cryptosporidiidae, found in the intestinal epithelium of many vertebrates including humans.Hyper-IgM Syndrome
Viral:
RotavirusRotavirusA genus of Reoviridae, causing acute gastroenteritis in birds and mammals, including humans. Transmission is horizontal and by environmental contamination. Seven species (rotaviruses A through G) are recognized.Rotavirus
NorovirusNorovirusNorovirus is a nonenveloped, single-stranded, positive-sense RNA virus belonging to the Caliciviridae family. Norovirus infections are transmitted via the fecal-oral route or by aerosols from vomiting. The virus is one of the most common causes of nonbacterial gastroenteritis epidemic worldwide. Symptoms include watery and nonbloody diarrhea, nausea, vomiting, and low-grade fever.Norovirus
AdenovirusAdenovirusAdenovirus (member of the family Adenoviridae) is a nonenveloped, double-stranded DNA virus. Adenovirus is transmitted in a variety of ways, and it can have various presentations based on the site of entry. Presentation can include febrile pharyngitis, conjunctivitis, acute respiratory disease, atypical pneumonia, and gastroenteritis.Adenovirus
CytomegalovirusCytomegalovirusCMV is a ubiquitous double-stranded DNA virus belonging to the Herpesviridae family. CMV infections can be transmitted in bodily fluids, such as blood, saliva, urine, semen, and breast milk. The initial infection is usually asymptomatic in the immunocompetent host, or it can present with symptoms of mononucleosis.Cytomegalovirus
Risk factors:
Contaminated food products:
Seafood
Poultry
Turkey
Eggs
Beef
Contaminated water
Animal exposure
High-risk environments for transmission:
Daycare
Nursing home
Hospital
Noninfectious diarrhea
Secretory:
LaxativesLaxativesLaxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient.Laxatives:
Vasoactive intestinal peptide-secretingtumorTumorInflammation (VIPomaVIPomaA VIPoma is a rare neuroendocrine tumor arising primarily in the pancreas that releases large amounts of vasoactive intestinal polypeptide (VIP). This process leads to chronic watery diarrhea with concomitant hypokalemia and dehydration, as well as wheezing and flushing (known as Verner-Morrison or WDHA syndrome).VIPoma)
GastrinomaGastrinomaA gastrinoma is a tumor that secretes excessive levels of the hormone gastrin and is responsible for Zollinger-Ellison syndrome (ZES). Gastrinomas are frequently associated with multiple endocrine neoplasia 1 (MEN 1) and can arise from the pancreas, stomach, duodenum, jejunum, and/or even from the lymph nodes.Gastrinoma
BileBileAn emulsifying agent produced in the liver and secreted into the duodenum. Its composition includes bile acids and salts; cholesterol; and electrolytes. It aids digestion of fats in the duodenum.Gallbladder and Biliary Tract: Anatomy acidmalabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion
Endocrine disease:
Addison’s diseaseAddison’s DiseaseAdrenal insufficiency (AI) is the inadequate production of adrenocortical hormones: glucocorticoids, mineralocorticoids, and adrenal androgens. Primary AI, also called Addison’s disease, is caused by autoimmune disease, infections, and malignancy, among others.Adrenal Insufficiency and Addison Disease
DiabetesDiabetesDiabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance.Diabetes Mellitus
Medications:
QuinineQuinineAn alkaloid derived from the bark of the cinchona tree. It is used as an antimalarial drug, and is the active ingredient in extracts of the cinchona that have been used for that purpose since before 1633. Quinine is also a mild antipyretic and analgesic and has been used in common cold preparations for that purpose. It was used commonly and as a bitter and flavoring agent, and is still useful for the treatment of babesiosis. Quinine is also useful in some muscular disorders, especially nocturnal leg cramps and myotonia congenita, because of its direct effects on muscle membrane and sodium channels. The mechanisms of its antimalarial effects are not well understood.Antimalarial Drugs
ColchicineColchicineA major alkaloid from colchicum autumnale l. And found also in other colchicum species. Its primary therapeutic use is in the treatment of gout.Gout Drugs
Antibiotics
DigoxinDigoxinA cardiotonic glycoside obtained mainly from digitalis lanata; it consists of three sugars and the aglycone digoxigenin. Digoxin has positive inotropic and negative chronotropic activity. It is used to control ventricular rate in atrial fibrillation and in the management of congestive heart failure with atrial fibrillation. Its use in congestive heart failure and sinus rhythm is less certain. The margin between toxic and therapeutic doses is small.Cardiac Glycosides
MisoprostolMisoprostolA synthetic analog of natural prostaglandin e1. It produces a dose-related inhibition of gastric acid and pepsin secretion, and enhances mucosal resistance to injury. It is an effective anti-ulcer agent and also has oxytocic properties.Eicosanoids
Magnesium sulfateMagnesium SulfateA small colorless crystal used as an anticonvulsant, a cathartic, and an electrolyte replenisher in the treatment of pre-eclampsia and eclampsia. It causes direct inhibition of action potentials in myometrial muscle cells. Excitation and contraction are uncoupled, which decreases the frequency and force of contractions.Laxatives ormagnesiumMagnesiumA metallic element that has the atomic symbol mg, atomic number 12, and atomic weight 24. 31. It is important for the activity of many enzymes, especially those involved in oxidative phosphorylation.Electrolytes hydroxide
Lactase deficiencyLactase deficiencyLactose Intolerance (lactose intoleranceLactose intoleranceLactose intolerance (LI) describes a constellation of symptoms due to lactase deficiency (LD), the enzyme located in the brush border of the absorptive cells in the small intestine. Lactose is the disaccharide present in milk and requires hydrolysis by lactase to break it down into its 2 absorbable constituents, glucose and galactose. Lactose intolerance typically presents with bloating, abdominal cramping, diarrhea, and flatulence.Lactose Intolerance)
NonabsorbablecarbohydratesCarbohydratesA class of organic compounds composed of carbon, hydrogen, and oxygen in a ratio of cn(H2O)n. The largest class of organic compounds, including starch; glycogen; cellulose; polysaccharides; and simple monosaccharides.Basics of Carbohydrates:
SorbitolSorbitolA polyhydric alcohol with about half the sweetness of sucrose. Sorbitol occurs naturally and is also produced synthetically from glucose. It was formerly used as a diuretic and may still be used as a laxative and in irrigating solutions for some surgical procedures. It is also used in many manufacturing processes, as a pharmaceutical aid, and in several research applications.Laxatives
LactuloseLactuloseA synthetic disaccharide used in the treatment of constipation and hepatic encephalopathy. It has also been used in the diagnosis of gastrointestinal disorders.Laxatives
IntraluminalmaldigestionMaldigestionMalabsorption involves many disorders in which there is an inability of the gut to absorb nutrients from dietary intake, potentially including water and/or electrolytes. A closely related term, maldigestion is the inability to break down large molecules of food into their smaller constituents. Malabsorption and maldigestion can affect macronutrients (fats, proteins, and carbohydrates), micronutrients (vitamins and minerals), or both.Malabsorption and Maldigestion:
Pancreatic exocrine insufficiency (e.g., chronicpancreatitisPancreatitisInflammation of the pancreas. Pancreatitis is classified as acute unless there are computed tomographic or endoscopic retrograde cholangiopancreatographic findings of chronic pancreatitis. The two most common forms of acute pancreatitis are alcoholic pancreatitis and gallstone pancreatitis.Acute Pancreatitis)
Bariatric surgeryBariatric surgeryBariatric surgery refers to a group of invasive procedures used to surgically reduce the size of the stomach to produce early satiety, decrease food intake (restrictive type) and/or alter digestion, and artificially induce malabsorption of nutrients (malabsorptive type). The ultimate goal of bariatric surgery is drastic weight loss.Bariatric Surgery
MucosalmalabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion:
Celiac diseaseCeliac diseaseCeliac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis.Celiac Disease
Whipple disease
MesentericischemiaIschemiaA hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation.Ischemic Cell Damage
UlcerativecolitisColitisInflammation of the colon section of the large intestine, usually with symptoms such as diarrhea (often with blood and mucus), abdominal pain, and fever.Pseudomembranous Colitis
MicroscopiccolitisColitisInflammation of the colon section of the large intestine, usually with symptoms such as diarrhea (often with blood and mucus), abdominal pain, and fever.Pseudomembranous Colitis
EosinophilicgastroenteritisGastroenteritisGastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration.Gastroenteritis
InfectionsInfectionsInvasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases.Chronic Granulomatous Disease
RadiationRadiationEmission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles).Osteosarcoma injury
ColonColonThe large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal.Colon, Cecum, and Appendix: Anatomy cancer
Irritable bowel syndromeIrritable bowel syndromeIrritable bowel syndrome (IBS) is a functional bowel disease characterized by chronic abdominal pain and altered bowel habits without an identifiable organic cause. The etiology and pathophysiology of this disease are not well understood, and there are many factors that may contribute.Irritable Bowel Syndrome (IBSIBSIrritable bowel syndrome (IBS) is a functional bowel disease characterized by chronic abdominal pain and altered bowel habits without an identifiable organic cause. The etiology and pathophysiology of this disease are not well understood, and there are many factors that may contribute.Irritable Bowel Syndrome)
Invasion of the mucosa by an infectious organism → inflammatory response and damage to theepitheliumEpitheliumThe epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions.Surface Epithelium: Histology → ↓absorptionAbsorptionAbsorption 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 and exudation of serum and blood into the lumen
Mucus, blood, andleukocytesLeukocytesWhite blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes).White Myeloid Cells: Histologycan be detected in the stool.
Noninflammatory/noninvasive:
Pathogens do not invade the mucosa.
Most often associated with bacterial enterotoxins → alter ion transport → efflux of ions and water into the bowel lumen
The mucosa remains normal or is only minimally altered.
Stools are watery and lack fecalleukocytesLeukocytesWhite blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes).White Myeloid Cells: Histology and blood.
Noninfectious diarrhea
Secretory:
ActivesecretionSecretionCoagulation Studies of water into the intestinal lumen due to activated ion transport systems
Diarrhea occurs throughout the day and night.
Pathogenesis of secretory diarrhea: Overactivation of ion transport channels can lead to secretion of electrolytes and water into the intestinal lumen, resulting in diarrhea. Ca2+: calcium CaCC: calcium-activated chloride channels cAMP: cyclic adenosine monophosphate CFTR: cystic fibrosis transmembrane conductance regulator Cl−: chloride K+: potassium Na+: sodium NKCC: sodium–potassium chloride cotransporter
Image by Lecturio.
Osmotic:
Water is drawn into the intestinal lumen by poorly absorbed substances.
Stool output is consistent with the amount of unabsorbable substance that is ingested.
Occurs during the day only, and stools ↓ with discontinuation of the offending substance
↑Osmolar gap will be seen.
Pathogenesis of lactase deficiency (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, flatulence, and abdominal pain.
Impaired nutrientabsorptionAbsorptionAbsorption 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 ordigestionDigestionDigestion refers to the process of the mechanical and chemical breakdown of food into smaller particles, which can then be absorbed and utilized by the body.Digestion and Absorption
Often results in fatty stools (steatorrhea)
Inflammatory/exudative:
InflammationInflammationInflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function.Inflammation →intestinal mucosaIntestinal MucosaLining of the intestines, consisting of an inner epithelium, a middle lamina propria, and an outer muscularis mucosae. In the small intestine, the mucosa is characterized by a series of folds and abundance of absorptive cells (enterocytes) with microvilli.Small Intestine: Anatomy damage → impairedabsorptionAbsorptionAbsorption 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
Mucus, blood, andleukocytesLeukocytesWhite blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes).White Myeloid Cells: Histologyarepresent in the stool.
AlteredmotilityMotilityThe motor activity of the gastrointestinal tract.Gastrointestinal Motility: rapid intestinal passage → ↓ time for fluidabsorptionAbsorptionAbsorption 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
Steatorrhea (likely frommalabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion)
Bloody (likely inflammatory)
Mucoid (likely inflammatory)
Associated symptoms:
FeverFeverFever 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
NauseaNauseaAn 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 andvomitingVomitingThe forcible expulsion of the contents of the stomach through the mouth.Hypokalemia (especially due to an infectious or toxin-mediated etiology)
DryskinSkinThe skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue.Skin: Structure and Functions and mucous membranes
FatigueFatigueThe state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.Fibromyalgia
TachycardiaTachycardiaAbnormally rapid heartbeat, usually with a heart rate above 100 beats per minute for adults. Tachycardia accompanied by disturbance in the cardiac depolarization (cardiac arrhythmia) is called tachyarrhythmia.Sepsis in Children
FeverFeverFever 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 ≥ 38.5°C (≥ 101°F)
High-risk population (elderly,immunocompromisedimmunocompromisedA human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation.GastroenteritispatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship, those with known inflammatory bowel disease)
Stool analysis:
FecalleukocytesLeukocytesWhite blood cells. These include granular leukocytes (basophils; eosinophils; and neutrophils) as well as non-granular leukocytes (lymphocytes and monocytes).White Myeloid Cells: Histology
Ova and parasites
Stool culture andpolymerase chain reactionPolymerase chain reactionPolymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules.Polymerase Chain Reaction (PCR) (PCRPCRPolymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules.Polymerase Chain Reaction (PCR))
Occult blood
Lactoferrin
C. difficile toxin immunoassay (particularly if there is recent antibiotic use)
Supporting laboratory evaluation:
Generally done only inpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship with severe disease and evidence ofdehydrationDehydrationThe condition that results from excessive loss of water from a living organism.Volume Depletion and Dehydration
Electrolyte abnormalities (hypokalemiaHypokalemiaHypokalemia is defined as plasma potassium (K+) concentration< 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake.Hypokalemia)
↑ Creatinine →acute kidney injuryAcute Kidney InjuryAcute kidney injury refers to sudden and often reversible loss of renal function, which develops over days or weeks. Azotemia refers to elevated levels of nitrogen-containing substances in the blood that accompany AKI, which include BUN and creatinine.Acute Kidney Injury fromdehydrationDehydrationThe condition that results from excessive loss of water from a living organism.Volume Depletion and Dehydration
Non–anion gapAnion gapMetabolic Acidosis metabolicacidosisAcidosisA pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up.Respiratory Acidosis
Chronic diarrhea
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:
Used to narrow the differential diagnosis
CBC → evaluate foranemiaAnemiaAnemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology.Anemia: Overview and Types (malabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion,malignancyMalignancyHemothorax)
Thyroid-stimulating hormoneThyroid-stimulating hormoneA glycoprotein hormone secreted by the adenohypophysis. Thyrotropin stimulates thyroid gland by increasing the iodide transport, synthesis and release of thyroid hormones (thyroxine and triiodothyronine).Thyroid Hormones → screen forhyperthyroidismHyperthyroidismHypersecretion of thyroid hormones from the thyroid gland. Elevated levels of thyroid hormones increase basal metabolic rate.Thyrotoxicosis and Hyperthyroidism
StoolelectrolytesElectrolytesElectrolytes 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 → calculate stool osmolar gap
Normal stoolosmolalityOsmolalityPlasma osmolality refers to the combined concentration of all solutes in the blood.Renal Sodium and Water Regulation = 290 mmol/L (same as serum)
The osmotic gap = 290 – 2 × (stoolsodiumSodiumA member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23.Hyponatremia + stoolpotassiumPotassiumAn 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)
Osmotic diarrhea: > 125 mmol/L
Secretory diarrhea: < 50 mmol/L
Occult blood → seen in inflammatory bowel disease,malignancyMalignancyHemothorax, and chronic infection
C. difficile toxin immunoassay (if history of antibiotic use)
Fecal fat →malabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion offatsFatsThe glyceryl esters of a fatty acid, or of a mixture of fatty acids. They are generally odorless, colorless, and tasteless if pure, but they may be flavored according to origin. Fats are insoluble in water, soluble in most organic solvents. They occur in animal and vegetable tissue and are generally obtained by boiling or by extraction under pressure. They are important in the diet (dietary fats) as a source of energy.Energy Homeostasis
FecalchymotrypsinChymotrypsinA serine endopeptidase secreted by the pancreas as its zymogen, chymotrypsinogen and carried in the pancreatic juice to the duodenum where it is activated by trypsin. It selectively cleaves aromatic amino acids on the carboxyl side.Pancreatic Parameters andelastaseElastaseA protease of broad specificity, obtained from dried pancreas. Molecular weight is approximately 25, 000. The enzyme breaks down elastin, the specific protein of elastic fibers, and digests other proteins such as fibrin, hemoglobin, and albumin.Proteins and Peptides → potential pancreatic insufficiency
LaxativeLaxativeAgents that produce a soft formed stool, and relax and loosen the bowels, typically used over a protracted period, to relieve constipation.Hypokalemia screen
Tests formalabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion:
FolateFolateFolate and vitamin B12 are 2 of the most clinically important water-soluble vitamins. Deficiencies can present with megaloblastic anemia, GI symptoms, neuropsychiatric symptoms, and adverse pregnancy complications, including neural tube defects.Folate and Vitamin B12
AlbuminAlbuminSerum albumin from humans. It is an essential carrier of both endogenous substances, such as fatty acids and bilirubin, and of xenobiotics in the blood.Liver Function Tests
25-Hydroxyvitamin D
Imaging and procedures:
Use of these methods is guided by the patient’s history, symptoms, presence of worrisome features, and clinical suspicion.
EndoscopyEndoscopyProcedures of applying endoscopes for disease diagnosis and treatment. Endoscopy involves passing an optical instrument through a small incision in the skin i.e., percutaneous; or through a natural orifice and along natural body pathways such as the digestive tract; and/or through an incision in the wall of a tubular structure or organ, i.e. Transluminal, to examine or perform surgery on the interior parts of the body.Gastroesophageal Reflux Disease (GERD) and/orcolonoscopyColonoscopyEndoscopic examination, therapy or surgery of the luminal surface of the colon.Colorectal Cancer Screening:
Should be performed promptly inpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship with alarming features:
Evidence ofmalabsorptionMalabsorptionGeneral term for a group of malnutrition syndromes caused by failure of normal intestinal absorption of nutrients.Malabsorption and Maldigestion
Visualization and mucosalbiopsyBiopsyRemoval and pathologic examination of specimens from the living body.Ewing Sarcoma can help diagnose:
Inflammatory bowel disease
Celiac diseaseCeliac diseaseCeliac disease (also known as celiac sprue or gluten enteropathy) is an autoimmune reaction to gliadin, which is a component of gluten. Celiac disease is closely associated with HLA-DQ2 and HLA-DQ8. The immune response is localized to the proximal small intestine and causes the characteristic histologic findings of villous atrophy, crypt hyperplasia, and intraepithelial lymphocytosis.Celiac Disease
MicroscopiccolitisColitisInflammation of the colon section of the large intestine, usually with symptoms such as diarrhea (often with blood and mucus), abdominal pain, and fever.Pseudomembranous Colitis
Includes specialized testing, such as enterography and cholangiopancreatography
Should be considered inpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship with:
FeverFeverFever 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
PancreasPancreasThe pancreas lies mostly posterior to the stomach and extends across the posterior abdominal wall from the duodenum on the right to the spleen on the left. This organ has both exocrine and endocrine tissue.Pancreas: Anatomy pathology
MostpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship will require only oralrehydrationRehydrationDengue Virus therapy.
IV fluid hydration should be used in severe disease.
Oral and IV solutions should contain replacementelectrolytesElectrolytesElectrolytes 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.
If possible, withdraw any potentially offending medications.
AntidiarrhealAntidiarrhealAntidiarrheal 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 agents:
Options:loperamideLoperamideOne of the long-acting synthetic antidiarrheals; it is not significantly absorbed from the gut, and has no effect on the adrenergic system or central nervous system, but may antagonize histamine and interfere with acetylcholine release locally.Antidiarrheal Drugs,bismuth subsalicylateBismuth SubsalicylateAntidiarrheal Drugs
Reduce the duration of diarrhea
Be aware that treatment can delay the extraction of pathogens and toxins.
ContraindicationsContraindicationsA condition or factor associated with a recipient that makes the use of a drug, procedure, or physical agent improper or inadvisable. Contraindications may be absolute (life threatening) or relative (higher risk of complications in which benefits may outweigh risks).Noninvasive Ventilation:
Diarrhea withfeverFeverFever 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
Bloody or mucoid stool
Diarrhea caused byC. difficileandShigellaShigellaShigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir.Shigella
FeverFeverFever 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
Severe symptoms requiringhospitalizationHospitalizationThe confinement of a patient in a hospital.Delirium
High-riskpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship (e.g., infants, elderly,immunocompromisedimmunocompromisedA human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation.Gastroenteritis)
SuspectedC. difficileinfection
Frequently used antibiotics:
FluoroquinolonesFluoroquinolonesFluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms.Fluoroquinolones
AzithromycinAzithromycinA semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis.Macrolides and Ketolides
TrimethoprimTrimethoprimThe sulfonamides are a class of antimicrobial drugs inhibiting folic acid synthesize in pathogens. The prototypical drug in the class is sulfamethoxazole. Although not technically sulfonamides, trimethoprim, dapsone, and pyrimethamine are also important antimicrobial agents inhibiting folic acid synthesis. The agents are often combined with sulfonamides, resulting in a synergistic effect.Sulfonamides and Trimethoprim–sulfamethoxazoleSulfamethoxazoleA bacteriostatic antibacterial agent that interferes with folic acid synthesis in susceptible bacteria. Its broad spectrum of activity has been limited by the development of resistance.Sulfonamides and Trimethoprim
3rd-generationcephalosporinsCephalosporinsCephalosporins are a group of bactericidal beta-lactam antibiotics (similar to penicillins) that exert their effects by preventing bacteria from producing their cell walls, ultimately leading to cell death. Cephalosporins are categorized by generation and all drug names begin with “cef-” or “ceph-.”Cephalosporins
Evaluation and management of patients with acute diarrhea: Based on the history and physical exam, a determination can be made about whether the diarrhea is related to an infectious or a noninfectious etiology (e.g., medications). Most patients 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.
Image by Lecturio.
Chronic diarrhea
The treatment of chronic diarrhea hinges on diagnosing and treating the underlying etiology.
Symptomatic therapy:
Indicated:
ForpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship who cannot tolerate definitive therapy
When no definitive diagnosis has been found
For temporary relief during workup
Options:
LoperamideLoperamideOne of the long-acting synthetic antidiarrheals; it is not significantly absorbed from the gut, and has no effect on the adrenergic system or central nervous system, but may antagonize histamine and interfere with acetylcholine release locally.Antidiarrheal Drugs
AnticholinergicsAnticholinergicsAnticholinergic drugs block the effect of the neurotransmitter acetylcholine at the muscarinic receptors in the central and peripheral nervous systems. Anticholinergic agents inhibit the parasympathetic nervous system, resulting in effects on the smooth muscle in the respiratory tract, vascular system, urinary tract, GI tract, and pupils of the eyes.Anticholinergic Drugs
May be used inpatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship in whom the diagnosis is highly suspected but who cannot tolerate testing
Lactose restriction → suspectedlactose intoleranceLactose intoleranceLactose intolerance (LI) describes a constellation of symptoms due to lactase deficiency (LD), the enzyme located in the brush border of the absorptive cells in the small intestine. Lactose is the disaccharide present in milk and requires hydrolysis by lactase to break it down into its 2 absorbable constituents, glucose and galactose. Lactose intolerance typically presents with bloating, abdominal cramping, diarrhea, and flatulence.Lactose Intolerance
CholestyramineCholestyramineA strongly basic anion exchange resin whose main constituent is polystyrene trimethylbenzylammonium cl(-) anion.Lipid Control Drugs:
Recent ileal resection
AbdominalradiationRadiationEmission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles).Osteosarcoma therapy
AftercholecystectomyCholecystectomyCholecystectomy is a surgical procedure performed with the goal of resecting and extracting the gallbladder. It is one of the most common abdominal surgeries performed in the Western world. Cholecystectomy is performed for symptomatic cholelithiasis, cholecystitis, gallbladder polyps > 0.5 cm, porcelain gallbladder, choledocholithiasis and gallstone pancreatitis, and rarely, for gallbladder cancer.Cholecystectomy
Diarrhea that develops after individuals from resource-rich settings return from travel to resource-limited regions:
Occurs in 40%–60% of travelers to resource-limited areas
May be inflammatory or secretory
Etiology (list is not exhaustive):
EnterotoxigenicE. coli is the most common cause.
Campylobacter jejuniCampylobacter jejuniA species of bacteria that resemble small tightly coiled spirals. Its organisms are known to cause abortion in sheep and fever and enteritis in man and may be associated with enteric diseases of calves, lambs, and other animals.Campylobacter
ShigellaShigellaShigella is a genus of gram-negative, non-lactose-fermenting facultative intracellular bacilli. Infection spreads most commonly via person-to-person contact or through contaminated food and water. Humans are the only known reservoir.Shigella
SalmonellaSalmonellaSalmonellae are gram-negative bacilli of the family Enterobacteriaceae. Salmonellae are flagellated, non-lactose-fermenting, and hydrogen sulfide-producing microbes. Salmonella enterica, the most common disease-causing species in humans, is further classified based on serotype as typhoidal (S. typhi and paratyphi) and nontyphoidal (S. enteritidis and typhimurium).Salmonella
GiardiaGiardiaA genus of flagellate intestinal eukaryotes parasitic in various vertebrates, including humans. Characteristics include the presence of four pairs of flagella arising from a complicated system of axonemes and cysts that are ellipsoidal to ovoidal in shape.Nitroimidazoles lamblia
NorovirusNorovirusNorovirus is a nonenveloped, single-stranded, positive-sense RNA virus belonging to the Caliciviridae family. Norovirus infections are transmitted via the fecal-oral route or by aerosols from vomiting. The virus is one of the most common causes of nonbacterial gastroenteritis epidemic worldwide. Symptoms include watery and nonbloody diarrhea, nausea, vomiting, and low-grade fever.Norovirus
Transmission:
Foodborne
Waterborne
Clinical presentation:
Symptoms begin 12–72 hours after ingestion of contaminated food or water.
NauseaNauseaAn 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 andvomitingVomitingThe forcible expulsion of the contents of the stomach through the mouth.Hypokalemia
Most cases are mild and do not require diagnostic evaluation.
Management:
Fluid replacement
AntidiarrhealAntidiarrhealAntidiarrheal 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 medications
Antibiotics
Not necessary
May be considered in moderate or severe disease
Options:fluoroquinolonesFluoroquinolonesFluoroquinolones are a group of broad-spectrum, bactericidal antibiotics inhibiting bacterial DNA replication. Fluoroquinolones cover gram-negative, anaerobic, and atypical organisms, as well as some gram-positive and multidrug-resistant (MDR) organisms.Fluoroquinolones orazithromycinAzithromycinA semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis.Macrolides and Ketolides
Factitious diarrhea andlaxativeLaxativeAgents that produce a soft formed stool, and relax and loosen the bowels, typically used over a protracted period, to relieve constipation.Hypokalemia abuse
Demographics:
Factitious diarrhea:
> 90% of cases are in women.
Significant proportion have worked in healthcare
ManypatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship will have a history of frequent hospital admissions.
LaxativeLaxativeAgents that produce a soft formed stool, and relax and loosen the bowels, typically used over a protracted period, to relieve constipation.Hypokalemia abuse:
ElderlypatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship who continue takinglaxativesLaxativesLaxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient.Laxatives after resolution ofconstipationConstipationConstipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency< 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic.Constipation
PatientsPatientsIndividuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures.Clinician–Patient Relationship withanorexiaAnorexiaThe lack or loss of appetite accompanied by an aversion to food and the inability to eat. It is the defining characteristic of the disorder anorexia nervosa.Anorexia Nervosa nervosa orbulimiaBulimiaEating an excess amount of food in a short period of time, as seen in the disorder of bulimia nervosa. It is caused by an abnormal craving for food, or insatiable hunger also known as ‘ox hunger’.Bulimia Nervosa nervosa
Etiology: surreptitious or inadvertent overuse oflaxativesLaxativesLaxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient.Laxatives
May alternate withconstipationConstipationConstipation is common and may be due to a variety of causes. Constipation is generally defined as bowel movement frequency< 3 times per week. Patients who are constipated often strain to pass hard stools. The condition is classified as primary (also known as idiopathic or functional constipation) or secondary, and as acute or chronic.Constipation
HyponatremiaHyponatremiaHyponatremia is defined as a decreased serum sodium (sNa+) concentration less than 135 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled via antidiuretic hormone (ADH) release from the hypothalamus and by the thirst mechanism.Hyponatremia
HypokalemiaHypokalemiaHypokalemia is defined as plasma potassium (K+) concentration< 3.5 mEq/L. Homeostatic mechanisms maintain plasma concentration between 3.5-5.2 mEq/L despite marked variation in dietary intake. Hypokalemia can be due to renal losses, GI losses, transcellular shifts, or poor dietary intake.Hypokalemia
HyperuricemiaHyperuricemiaExcessive uric acid or urate in blood as defined by its solubility in plasma at 37 degrees c; greater than 0. 42 mmol per liter (7. 0 mg/dl) in men or 0. 36 mmol per liter (6. 0 mg/dl) in women.Gout
MetabolicalkalosisAlkalosisA pathological condition that removes acid or adds base to the body fluids.Respiratory Alkalosis (with chronic use)
HypermagnesemiaHypermagnesemiaElectrolytes (with magnesium-containinglaxativesLaxativesLaxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient.Laxatives)
ScreeningScreeningPreoperative Care tests forlaxativesLaxativesLaxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient.Laxatives may help determine the cause.
BiopsyBiopsyRemoval and pathologic examination of specimens from the living body.Ewing Sarcoma shows lipofuscin-ladenmacrophagesMacrophagesThe relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells.Innate Immunity: Phagocytes and Antigen Presentation.
Barium enema:
“CatharticcolonColonThe large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal.Colon, Cecum, and Appendix: Anatomy” (largebowel dilationBowel dilationLarge Bowel Obstruction with ↓ or absent haustrations)
Most likely seen in the rightcolonColonThe large intestines constitute the last portion of the digestive system. The large intestine consists of the cecum, appendix, colon (with ascending, transverse, descending, and sigmoid segments), rectum, and anal canal. The primary function of the colon is to remove water and compact the stool prior to expulsion from the body via the rectum and anal canal.Colon, Cecum, and Appendix: Anatomy
DiscontinuelaxativesLaxativesLaxatives are medications used to promote defecation. Most often, laxatives are used to treat constipation or for bowel preparation for certain procedures. There are 4 main classes of laxatives: bulk-forming, stimulant, osmotic, and emollient.Laxatives.
Treat underlying psychologic issues.
Melanosis coli, due to laxative abuse, as seen on colonoscopy
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
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