29 Diarrhea, Constipation, and Probiotics (1) Flashcards
1
Q
Definition of diarrhea
- Diarrhea and constipation
- Diarrhea
- used to define diarrhea clinically
- standard definition of diarrhea
- exceptions to this definition.
A
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Diarrhea and constipation
- common
- both can also be a symptom of other, more serious underlying conditions and can be chronic in nature
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Diarrhea,
- increased liquidity of stool with or without increased frequency of stool.
- stool frequency or stool weight is used to define diarrhea clinically.
- Three or more bowel movements per day or stool weight greater than 200 g per day are considered the standard definition of diarrhea.
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exceptions to this definition.
- Indian and native African diets have a high fiber content, and hence they have increased stool weight (> 200 g/day) but do not have diarrhea because they have normal stool consistency and frequency (< 3/day).
- other patients have normal stool weight but complain of diarrhea because their stools are loose or watery (but frequency is < 3/day).
2
Q
Regulation of Absorptive and Secretory Processes in the Intestine
- Epithelial cells in the small intestine/
- Secretory processes/
- absorptive processes/
- Almost all diarrheal disorders are associated with/
- Absorptive and secretory processes are regulated by
A
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Epithelial cells in the small intestine originate in the crypt, have a spatial distribution along the crypt–villous axis, and then migrate to the tip of the villus, where they slough into the lumen.
- Secretory processes generally occur in crypt cells,
- absorptive processes occur in villous cells. Enteroendocrine cells are sparse but are present in the crypt.
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Almost all diarrheal disorders are associated with net fluid secretion.
- This secretion is most often secondary to the stimulation of active chloride secretion and to the inhibition of active absorption of sodium and chloride (by messengers such as cyclic AMP) which involves the coupling of sodium–hydrogen exchange and chloride–bicarbonate exchange.
- Absorptive and secretory processes are regulated by both the enteric nervous system and enteric hormones,
3
Q
Review of Normal Physiology
- The small intestine and colon are involved in/
- Alterations in fluid and electrolyte handling contribute to
- Alterations in motor and sensory functions of the colon may result in/
- The small intestine and colon normally absorb/
- The colon has a large capacitance and functional reserve and may recover/
- A reduction of water absorption by as little as 1% can cause/
- The distal ileum acts as/
- Segmentation by haustra/
- The ascending and transverse colon function as/
- the descending colon acts as/
- The colon is efficient at/
- Diarrhea or constipation may result from/
A
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The small intestine and colon are involved in secretion and absorption of water and electrolytes, storage and subsequent transport of intraluminal contents, and the salvage of some nutrients after bacterial metabolism of carbohydrates that are not absorbed in the small intestine.
- Alterations in fluid and electrolyte handling contribute to diarrhea.
- Alterations in motor and sensory functions of the colon may result in common conditions such as irritable bowel syndrome, chronic diarrhea, and chronic constipation.
- The small intestine and colon normally absorb 99% of the total fluid load of about 10 L/day presented to it. Approximately 1 L of residual fluid reaches the colon; the stool excretion of fluid constitutes about 0.2 L/d, indicating that 0.8 L/d are absorbed in the colon.
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The colon has a large capacitance and functional reserve and may recover up to four times its usual volume provided the rate of flow permits reabsorption to occur.
- Thus, the colon can partially compensate for intestinal absorptive or secretory disorders.
- A reduction of water absorption by as little as 1% can cause diarrhea.
- The distal ileum acts as a reservoir, emptying intermittently by bolus movements. This action allows time for salvage of fluids, electrolytes, and nutrients.
- Segmentation by haustra compartmentalizes the colon and facilitates mixing, retention of residue, and formation of solid stools.
- The ascending and transverse colon function as reservoirs
- the descending colon acts as a conduit.
- The colon is efficient at conserving sodium and water, a functions that are particularly important in sodium-depleted patients in whom the small intestine alone is unable to maintain sodium balance.
- Diarrhea or constipation may result from alterations in the reservoir function of the proximal colon, or the propulsive function of the left colon.
4
Q
Pathophysiology and mechanisms of diarrhea
- absorption vs. secretion in the intestines
- what can lead to diarrhea
- When infectious agents, toxins, or other noxious substances are present within the gut/
- There are four major mechanisms of diarrhea:
A
- Normally, absorption is quantitatively greater than secretion in the intestines.
- either a decrease in absorption or an increase in secretion can lead to diarrhea.
- When infectious agents, toxins, or other noxious substances are present within the gut, fluid secretion and motility are stimulated to expel the unwanted material, producing diarrhea.
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There are four major mechanisms of diarrhea:
- the presence in the gut lumen of unusual amounts of poorly absorbable, osmotically active solutes (osmotic diarrhea);
- intestinal ion secretion or inhibition of normal active ion absorption (secretory diarrhea);
- deranged intestinal motility;
- exudation of mucus, blood, and protein from sites of inflammation.
5
Q
Osmotic Diarrhea
- what leads to diarrhea of the osmotic type
- The intestines cannot maintain an osmotic gradient; thus/
- Disaccharides (sucrose and lactose) require/
- Lactose intolerance results due to/
- Lactulose
- The essential characteristic of osmotic diarrhea
- Associated with a stool osmolal gap/
A
- Ingestion of poorly absorbed sugars or alcohols (e.g., mannitol, sorbitol) or ions (as found in laxatives - magnesium, sulfate, and phosphate) leads to diarrhea of the osmotic type.
- The intestines cannot maintain an osmotic gradient; thus, these unabsorbed ions in the intestinal lumen cause retention of water to maintain an intraluminal osmolality closer to that of body fluids (about 290 mOsm/kg).
- Disaccharides (sucrose and lactose) require disaccharidase for breakdown prior to absorption.
- Lactose intolerance results due to a deficiency of disaccharidase lactase, a common clinical situation associated with normal aging in many ethnic groups as well as diseases of the upper small intestine.
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Lactulose,
- a synthetic disaccharide, cannot be hydrolyzed by the human intestine
- cannot be absorbed intact in greater than trace amounts.
- causes an osmotic diarrhea when given in sufficient quantity to overwhelm the metabolic capacity of colonic bacteria (about 80 g/day).
- The essential characteristic of osmotic diarrhea is that it disappears with fasting or cessation of ingestion of the offending substance.
- **Associated with a stool osmolal gap greater than 100 mOsm/kg
6
Q
Secretory Diarrhea
- mechanism for diarrhea
- The most common cause for secretory diarrhea
- Peptides
- produced by/
- cause secretory diarrhea by/
- significant loss of surface area of intestines/
- In some cases the problem is temporary, because/
- Associated with a stool osmolal gap/
A
- Either net secretion of chloride or bicarbonate or inhibition of net sodium absorption is the mechanism for diarrhea.
-
The most common cause for secretory diarrhea is infection.
- Infectious agents (bacteria, parasites and viruses) produce enterotoxins that interact with receptors and lead to increased anion secretion;
- enterotoxins may block specific absorptive pathways (e.g. Na-H exchange).
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Peptides
- produced by endocrine tumors such as vasoactive intestinal peptide (VIP) or calcitonin
- cause secretory diarrhea by stimulating secretion by epithelial cells.
- Even though there is a large reserve absorptive capacity in both the small intestine and the colon, significant loss of surface area of intestines (e.g. after resective surgery, inflammatory bowel disease), may compromise water absorption and cause diarrhea.
- In some cases the problem is temporary, because over time the intestine may improve its capacity for absorption by the process of adaptation.
- **Associated with a stool osmolal gap less than 50 mOsm/kg
7
Q
Bile Salt Diarrhea
- Bile acids (bile salts)/
- The main role of bile salts
- Greater than 95% of the bile salts/
- The enterohepatic circulation of bile salts takes place/
- short gut syndrome
- treatment
A
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Bile acids (bile salts) are produced in the liver, secreted into the system, and stored in the gallbladder.
- The main role of bile salts is the absorption of lipids in the small intestine.
- Greater than 95% of the bile salts are absorbed in the terminal ileum, taken up by the liver and resecreted.
- The enterohepatic circulation of bile salts takes place about 5-6 times per day, leaving very little to enter the large bowel.
- Individuals with ‘short gut syndrome,’ such as Crohn’s disease patients who have had a major portion of their small intestine—including the terminal ileum—resected often have large amounts of bile salts enter the large bowel, stimulating water secretion and intestinal motility in the colon, which causes symptoms of chronic diarrhea.
- Bile salt binders, such as cholestyramine, are given to these patients.
8
Q
Neurohormonal Diarrhea (deranged motility)
- Because rapid transit prevents adequate time for absorption/
- increased intestinal transit is linked to/
- Corticotrophin releasing factor (CRF) receptors in the brain and the gut are important mediators of/
- common causes of neurohormonal diarrhea.
- Many endocrine diarrheas, such as those due to peptide-secreting tumors or hyperthyroidism, may lead to diarrhea not only by/
- Conversely, slow intestinal transit (deranged motility) may lead to/
- Bacterial overgrowth is common in conditions such as/
- Excess bacteria in the small intestine/
- Caffeine and methylxanthine drugs (theophylline and aminophylline) may cause/
A
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Because rapid transit prevents adequate time for absorption, diarrhea may result despite intact mucosal absorptive capacity.
- In disorders such as diabetes mellitus, postvagotomy diarrhea, postprandial diarrhea, and irritable bowel syndrome (IBS), increased intestinal transit is linked to abnormal enteric nervous system function.
-
Corticotrophin releasing factor (CRF) receptors in the brain and the gut are important mediators of acute or chronic stress–related alterations of gut function.
- This is why anxiety and other emotional issues are common causes of neurohormonal diarrhea.
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Many endocrine diarrheas, such as those due to peptide-secreting tumors or hyperthyroidism, may lead to diarrhea not only by effects on intestinal electrolyte transport but also by accelerating intestinal motility.
- Conversely, slow intestinal transit (deranged motility) may lead to a secretory diarrhea by promoting bacterial overgrowth in the small intestine.
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Bacterial overgrowth is common in conditions such as diabetes and collagen vascular diseases (scleroderma/systemic sclerosis).
- Excess bacteria in the small intestine disrupt digestion and may alter electrolyte transport.
- Caffeine and methylxanthine drugs (theophylline and aminophylline) may cause neurohormonal diarrhea via CNS stimulation.
9
Q
Other Types of Diarrhea (p.21-25)
- Exudative Diarrhea:
- Complex (mixed) Diarrhea:
- Chronic Diarrhea
A
-
Exudative Diarrhea:
- Disruption of the integrity of the intestinal mucosa
- due to inflammation and ulceration (bacillary dysentery, IBD)
- results in discharge of mucus, proteins, and blood into the bowel lumen.
- The net result is that colonic absorption of water and electrolytes is severely impaired.
-
Complex (mixed) Diarrhea:
- Rather than being produced by a single pathophysiologic mechanism, diarrhea is often produced by a combination of mechanisms.
- For example, a patient with malabsorption syndromes might have
- diarrhea because of the osmotic effects of unabsorbed carbohydrates
- secretory diarrhea because of inhibition of colonic absorption by the unabsorbed long-chain fatty acids.
- Celiac disease is a classic type of mixed diarrhea which is a combination of osmotic diarrhea (malabsorption) and secretory diarrhea (crypt hypertrophy).
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Chronic Diarrhea
- diarrhea that lasts longer than 4 weeks.
- Diarrhea that lasts from 2-4 weeks in duration is classified as persistent diarrhea and is often a consequence of infectious diarrhea (i.e. it’s a post-infectious diarrhea where small bowel regeneration and restoration of function is occurring gradually so a certain degree of diarrhea persists).
- diarrhea that is chronic simply indicates it isn’t getting better.
- Managing chronic diarrhea focuses on defining the underlying cause and involves a more sophisticated workup.
- Taking a detailed history of the symptoms of diarrhea may help not only to accurately diagnose the cause, but may avoid putting the patient through a myriad of unnecessary tests.
10
Q
Example of Causes of Chronic Diarrhea
- Neurohormonal
- Osmotic
- Secretory
- Exudative/inflammatory
A
-
Neurohormonal
- Anxiety, severe stress, nicotine, methylxanthines, distance running/intensive athletics
-
Osmotic
- Carbohydrate malabsorption
- Pernicious anemia
- Osmotic laxatives (magnesium, phosphate, sulfate)
- Malabsorption syndromes—short gut syndrome, celiac disease, Whipple’s disease, small bowel bacterial overgrowth
- Maldigestion—pancreatic exocrine insufficiency (cystic fibrosis, pancreatitis), inadequate luminal bile acids
- Radiation colitis
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Secretory
- Bacterial toxins
- Congenital syndromes
- Drugs and poisons; laxative abuse
- Vasculitis
- Disordered motility or regulation
- Endocrine diarrhea (hyperthyroidism, hypothyroidism, Addison’s disease, gastrinoma, VIPoma, somatostatinoma, carcinoid syndrome, medullary thyroid carcinoma)
- Other tumors (colon adenocarcinoma, lymphoma, villous adenoma)
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Exudative/inflammatory
- Inflammatory bowel disease
- Infectious disease
11
Q
Chronic Diarrhea Workup (p.9)
- History of present illness
- Physical Exam
- Labs/Radiology
- Initial
- Follow up
A
-
History of present illness
- Onset/frequency/consistency/volume
- Abdominal pain
- Blood/mucus
- Dizziness
- Fever
- Fluid intake
- Food/water exposure
- Headache
- Myalgia
- Nausea/vomiting
- Travel
- Weight loss
-
Physical Exam
- Hypotension, tachycardia, fever
- Orthostasis
- Abdominal tenderness/rebound/guarding
- Bowel sounds
- Abdominal mass
-
Labs/Radiology
-
Initial
- Electrolytes
- BUN/Creatinine
- CBC
- Initial Stool WBC
- Stool RBC
- Stool culture
- Stool ova and parasites
-
Follow up
- Blood cultures
- Abdominal radiograph
- Sigmoidoscopy
- Duodenal aspirate
-
Initial
12
Q
Constipation
- Bowel frequency ranges from/
- constipation is defined as/
- Most patients also have complaints such as/
- more common in/
- may also indicate/
- occurs because of /
- a consequence of two mechanisms:
A
- Bowel frequency ranges from three times a day to three times a week in the normal population.
-
constipation is defined as having a bowel movement fewer than three times per week.
- Constipation is a subjective experience and simply classifying constipation as the frequency of defecation may not address some significant symptomotology.
- Most patients also have complaints such as straining when trying to have a bowel movement, abdominal bloating and/or pain, incomplete evacuation, hard or small/hard stools, and sometimes a need for digital or positional manipulation to enable defecation.
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more common in
- young children, women and adults ages 65 and older.
- pregnant women and following childbirth or surgery.
- particularly distressing to children and is known to diminish the perceived quality of life for adults.
- may be a benign, functional occurrence due to diet or lifestyle factors,
- may also indicate much more serious underlying health problems, such as colonic dysmotility or obstructive cancerous lesions.
-
occurs because of
- an alteration in stool consistency, colonic motility or caliber.
- a change in the process of rectal evacuation.
-
a consequence of two mechanisms:
- obstruction of the movement of luminal contents
- decreased colonic propulsive activity.
13
Q
Rome III Criteria for Defining Chronic Functional Constipation
- useful for/
- Adults:
- Two or more of the following:
- Loose stools/
- Children:
- Must include one month of at least two of the following in infants up to 4 years of age
- Accompanying symptoms include/
A
-
useful for diagnosing functional—i.e. non-organic—constipation and to establish inclusion criteria for recruitment into clinical trials.
- used less frequently in normal clinical settings.
-
Adults:
-
Two or more of the following:
- Straining in at least 25% of defecations
- Lumpy or hard stools in more than 25% of defecations
- Sensation of incomplete evacuation in more than 25% of defecations
- Sensation of anorectal obstruction/blockage in more than 25% of defecations
- Manual maneuvers (digital evacuation, support of the pelvic floor) to facilitate more than 25% of evacuations
- Fewer than three defecations per week
- *Loose stools are not present and there are insufficient criteria for the diagnosis of irritable bowel syndrome
-
Two or more of the following:
-
Children:
-
Must include one month of at least two of the following in infants up to 4 years of age
- Two or fewer defecations per week
- At least one episode per week of incontinence after the acquisition of toileting skills
- History of excessive stool retention
- History of painful or hard bowel movements
- Presence of a large fecal mass in the rectum
- History of large diameter stool which may obstruct the toilet
- *Accompanying symptoms include irritability, decreased appetite, and/or early satiety.
- The accompanying symptoms disappear immediately following passage of a large stool.
-
Must include one month of at least two of the following in infants up to 4 years of age
14
Q
Selected causes of constipation
- Functional
- Structural
- Endocrine and metabolic conditions
- Neurogenic conditions
- Connective tissue/smooth muscle diseases
- Psychogenic conditions
- Neuromuscular conditions
- Medications
- etiology of constipation may differ between adults and children.
- Hirschsprung’s Disease
- Stress and lifestyle
A
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Functional
- Dietary factors (low fiber/residue intake), motility disorders (slow transit, outlet delay, irritable bowel syndrome), physical inactivity, sedentary lifestyle
-
Structural
- Colonic strictures (diverticulosis, ischemia, radiation therapy), colonic mass lesions with obstruction (adenocarcinoma), idiopathic megarectum, anorectal disorders (anal or perianal fissures, thrombosed hemorrhoids)
-
Endocrine and metabolic conditions
- Hypothyroidism, hypokalemia, diabetes mellitus (especially with poor glycemic control), hypercalcemia, hyperparathyroidism, uremia, pregnancy
-
Neurogenic conditions
- Cerebrovascular events, multiple sclerosis, Parkinson’s disease, spinal cord tumors
-
Connective tissue/smooth muscle diseases
- Amyloidosis, scleroderma/systemic sclerosis, systemic lupus erythematosus, mixed connective tissue disease
-
Psychogenic conditions
- Anxiety, depression, somatization, post-traumatic stress disorder (PTSD)
-
Neuromuscular conditions
- Hirschsprung’s disease (agangliosis), Chagas’ disease, botulism (in infants), pseudo-obstruction syndrome
-
Medications
- Antacids, anticholinergics, antidepressants, calcium channel blockers, cholestyramine (Questran), clonidine (Catapres), diuretics, levodopa (e.g., with carbidopa [Sinemet]), narcotics, NSAIDs, psychotropics, sympathomimetics, anticonvulsants
-
etiology of constipation may differ between adults and children.
-
Hirschsprung’s Disease
- a birth defect
- born without intestinal nerve ganglion cells, usually just in the area near the rectum but occasionally in the entire large intestine.
- Stress and lifestyle are important components of a patient’s history.
-
Hirschsprung’s Disease
15
Q
History
- detailed history of the patient’s present symptoms,
- “red flags” that suggest the presence of an underlying gastrointestinal organic disorder.
- Diet
- Lifestyle and activities
- Work
- Psychosocial history
- Cigarette smoking, alcohol consumption and any illicit drug use
A
- _ detailed history of the patient’s present symptoms,_
- ask what was the former ‘normal’ for the patient’s bowel habits, establish when the change in bowel habits occurred
- record the current frequency, consistency and color of bowel movements.
- note whether the patient has seen any blood or mucous in the stool. T
-
“red flags” that suggest the presence of an underlying gastrointestinal organic disorder.
- abdominal pain, nausea, cramping, vomiting, weight loss, melena, rectal bleeding, rectal pain, and sustained fever.
-
Diet
- fiber intake (fruits, vegetables, whole grains, fiber supplements)
- constipating foods (cheese, nuts, eggs, meat, granola, protein bars or drinks, etc)
- as well as average fluid intake, including constipating beverages such as dairy products, coffee, tea, energy drinks and soda.
- A low-fiber diet also plays a key role in constipation among older adults, especially if they choose foods that are quick to make or buy, such as fast foods, or prepared foods, both of which are usually low in fiber.
- Difficulties with chewing or swallowing may cause older people to eat soft foods that are processed and low in fiber.
-
Lifestyle and activities
- how much daily exercise the patient gets
- whether there been any recent changes to both recreational and non-recreational activity level
-
Work
- what the patient does for a living
- how much sedentary time is involved
- changes in work activities
- travel; many people develop constipation when they travel due to changes in eating, drinking and/or exercise habits as well as the dehydrating effect of air travel
-
Psychosocial history
- depression and constipation commonly co-occur.
- recent major life stressors
- signs of dysthymia or depression (eating/sleeping more or less than usual, anhedonia, etc.)
-
Cigarette smoking, alcohol consumption and any illicit drug use
- any changes in these behaviors.
- Quitting smoking often causes constipation.
