Chapter 43 - Diarrhea Flashcards
one of the most common causes of mortality in developing
countries, particularly among impoverished infants, accounting for
1.8 million deaths per year.
Acute infectious diarrhea
results in environmental enteropathy with long-term
impacts on physical and intellectual development.
Recurrent, acute diarrhea in children in
tropical countries
primary function of the small intestine
digestion and
assimilation of nutrients from food
function of small intestine and colon
regulate the secretion and
absorption of water and electrolytes, the storage and subsequent
transport of intraluminal contents aborally, and the salvage of some
nutrients
Alterations in motor and sensory functions of the colon result in highly
prevalent syndromes such as _______, _______, and _________
irritable bowel syndrome (IBS), chronic
diarrhea, and chronic constipation
also called the enteric nervous system, comprises
myenteric, submucosal, and mucosal neuronal layers
intrinsic innervation
regulates smooth-muscle function through intermediary pacemaker-
like cells called the interstitial cells of Cajal
myenteric
plexus
affects secretion, absorption, and mucosal blood flow
submucosal
plexus
receives input from the extrinsic nerves, but it
is capable of independent control of these functions.
enteric nervous system
innervations of the small intestine and colon are part of
the autonomic nervous system and also modulate motor and secretory
functions.
extrinsic innervations
convey visceral sensory pathways
from and excitatory pathways to the small intestine and colon
parasympathetic nerves
Parasympathetic fibers via the vagus nerve reach the small intestine
and proximal colon along the branches of the
superior mesenteric
artery
distal colon is supplied
sacral parasympathetic nerves
(S2–4) via the pelvic plexus
chief excitatory neurotransmitters
controlling motor function
acetylcholine and the tachykinins,
such as substance P
modulates motor
functions and reaches the small intestine and colon
sympathetic nerve supply
Sympathetic input to the gut is generally __________ to
sphincters and ________ to non-sphincteric muscle
excitatory
inhibitory
___ of fluid enter the GI tract, ___ of residual fluid
reaches the colon, and the stool excretion of fluid constitutes about
_____.
9L
~1 L
0.2 L/d
During the fasting period, the motility of the small intestine is characterized
by a cyclical event called the ___________),
which serves to clear nondigestible residue from the small intestine
(the intestinal “housekeeper”).
migrating motor complex (MMC)
MMC lasts for how long and occurs every???
lasts for 4min and occurs every 60-90min
acts as a reservoir, emptying intermittently by bolus
movements. This action allows time for salvage of fluids, electrolytes,
and nutrients.
distal ileum
Segmentation by ______
compartmentalizes the colon and
facilitates mixing, retention of residue,
and formation of solid stools
haustra
The resident microorganisms, predominantly \_\_\_\_\_\_\_\_\_\_, in the colon are necessary for the digestion of unabsorbed carbohydrates that reach the colon even in health, thereby providing a vital source of nutrients to the mucosa.
anaerobic bacteria
regions
of colon function as reservoirs (average
transit time,____)
ascending and transverse regions
15h
region of the colon that acts as a conduit (average transit time, ____).
descending colon
3h
efficient
at conserving sodium and water, a function that is particularly important
in sodium-depleted patients in whom the small intestine alone
is unable to maintain sodium balance
colon
result from alteration in the reservoir function of the proximal colon
or the propulsive function of the left colon.
Diarrhea or constipation
result from disturbances of the rectal or sigmoid reservoir, typically
as a result of dysfunction of the pelvic floor, the anal sphincters, the
coordination of defecation, or dehydration.
constipation
associated with mass movements through the colon and
normally occur approximately five times per day, usually on awakening
in the morning and postprandially
short duration or phasic contractions
high-amplitude (>75 mmHg) propagated contractions (HAPCs)
refers to the background contractility upon which
phasic contractile activity (typically contractions lasting <15 s) is superimposed
Colonic tone
After meal ingestion, colonic phasic and tonic contractility increases for
a period of ____
~2 h
The initial phase (~10 min) is mediated by the ______ in response to mechanical distention of the stomach
vagus nerve
Tonic contraction of the ____________, which forms a sling
around the rectoanal junction, is important to maintain continence
puborectalis muscle
during defecation, ______________ relax this muscle,
facilitating the straightening of the rectoanal angle
sacral parasympathetic nerves
Distention
of the rectum results in transient relaxation of the internal anal
sphincter via _______________.
intrinsic and reflex sympathetic innervation
loosely defined as passage of abnormally liquid or
unformed stools at an increased frequency
Diarrhea
diarrhea in adults
typical
Western diet, stool weight >200 g/d
acute diarrhea
<2 weeks
persistent diarrhea
2-4 weeks
chronic diarrhea
> 4 weeks
frequent
passage of small volumes of stool, is often associated with rectal
urgency, tenesmus, or a feeling of incomplete evacuation, and accompanies
IBS or proctitis
Pseudodiarrhea
involuntary discharge of
rectal contents and is most often caused by neuromuscular disorders
or structural anorectal problems
Fecal incontinence
may occur in nursing
home patients due to fecal impaction that is readily detectable by rectal
examination.
Overflow diarrhea
More than 90% of cases of acute diarrhea are caused by ______________
infectious
agents
acute diarrhea is accompanied by_________
vomiting, fever, and
abdominal pain
Disturbances of flora by antibiotics can lead to diarrhea
by reducing the digestive function or by allowing the overgrowth of
pathogens, such as ____________
Clostridium difficile
five high-risk groups in US
- Travelers
- Consumers of certain foods
- Immunodeficient persons
- Daycare attendees and their family members
- Institutionalized persons
Nearly 40% of tourists to endemic regions of Latin America,
Africa, and Asia develop so-called traveler’s diarrhea, most commonly
due to __________
enterotoxigenic or enteroaggregative Escherichia coli as
well as to Campylobacter, Shigella, Aeromonas, norovirus, Coronavirus,
and Salmonella
Visitors to Russia (especially St. Petersburg) may
have increased risk of _________
Giardia-associated diarrhea
Campers, backpackers, and swimmers in
wilderness areas may become infected with __________
Giardia
Cruise ships
may be affected by outbreaks of gastroenteritis caused by agents
such as ______
norovirus
chicken
Salmonella, Campylobacter, or Shigella
undercooked hamburger
enterohemorrhagic
E. coli (O157:H7)
fried rice or other reheated food
Bacillus cereus
mayonnaise or creams
Staphylococcus aureus or
Salmonella
eggs
Salmonella
fresh or frozen uncooked foods or soft cheeses
Listeria
seafood
Vibrio species,
Salmonella, or acute hepatitis A
primary immunodeficiency
IgA deficiency,
common variable hypogammaglobulinemia, chronic granulomatous
disease
secondary immunodeficiency
states
AIDS, senescence, pharmacologic suppression
In patients with AIDS, agents
transmitted venereally per rectum or by extension from vaginal
infection (e.g., Neisseria gonorrhoeae, Treponema pallidum, Chlamydia)
may contribute to ________
proctocolitis
most common microorganism in institutionalized persons
C. difficile
Profuse, watery diarrhea secondary to small-bowel hypersecretion
occurs with _____________, _______________, ____________
ingestion of preformed bacterial toxins
enterotoxin-
producing bacteria
enteroadherent pathogens
Diarrhea
associated with marked vomiting and minimal or no fever may occur
abruptly within a few hours
ingestion of preformed bacterial toxins
enterotoxin-
producing bacteria
vomiting is usually less, abdominal cramping or bloating is greater,
and fever is higher
enteroadherent pathogens
cause high fever and abdominal pain
Cytotoxin-producing and invasive
microorganisms
cause bloody diarrhea
Invasive
bacteria and Entamoeba histolytica
bloody diarrhea
dysentery
invades the terminal ileal and proximal colon
mucosa and may cause especially severe abdominal pain with tenderness
mimicking acute appendicitis
Yersinia
Reactive arthritis (formerly known as Reiter’s syndrome),
arthritis, urethritis, and conjunctivitis may accompany or follow infections
by _______, ____________, ________, _______.
Salmonella, Campylobacter, Shigella, and Yersinia
may
also lead to an autoimmune-type thyroiditis, pericarditis, and glomerulonephritis.
Yersiniosis
can
lead to the hemolytic-uremic syndrome with an attendant high mortality
rate
enterohemorrhagic E. coli (O157:H7) and Shigella
recognized as
a complication of infectious diarrhea
postinfectious IBS
may precede the diagnosis of celiac disease or Crohn’s disease
acute gastroenteritis
most
common noninfectious causes of acute diarrhea, and etiology may be
suggested by a temporal association between use and symptom onset
Side effects from medications
frequently incriminated medications that may produce diarrhea
antibiotics, cardiac antidysrhythmics,
antihypertensives, nonsteroidal anti-inflammatory drugs
(NSAIDs), certain antidepressants, chemotherapeutic agents, bronchodilators,
antacids, and laxatives
typically occurs in persons aged >50 years; often presents as
acute lower abdominal pain preceding watery, then bloody diarrhea;
and generally results in acute inflammatory changes in the sigmoid or
left colon while sparing the rectum
Occlusive or nonocclusive ischemic
colitis
Indications for evaluation in acute diarrhea
profuse diarrhea with
dehydration,
grossly bloody stools,
fever ≥38.5°C (≥101°F)
duration
>48 h without improvement, recent antibiotic use, new community
outbreaks, associated severe abdominal pain in patients aged
>50 years, and elderly (≥70 years) or immunocompromised patients