Pathology of the GI Tract- SI and Colon (6) Flashcards
infectious enterocolitis presents with a broad range of symptoms including what?
diarrhea, abdominal pain, urgency, perianal discomfort, incontinence, and hemorrhage
what should the diagnostic tests for infectious enterocolitis be driven by?
clinical history
few or no leukocytes and many erythrocytes in fecal test suggests what?
amebiasis
what are the characteristics of vibrio cholerae?
they are comma-shaped, gram negative bacteria
what is cholera?
a disease that has been endemic in the Ganges Valley of India and Bangladesh throughout history
how are the stools described in cases of cholera?
rice water stools with a fishy odor
what is the most common bacterial enteric pathogen in developed countries and is an important cause of traveler’s diarrhea?
C. jejuni
what causes campylobacter enterocolitis?
c. jejuni
how does one typically get c. jejuni?
improperly cooked chicken, unpasteurized milk, or contaminated water
how does campylobacter enterocolitis present?
watery or bloody diarrhea; enteric fever; reactive arthritis , guillain-barre, and erythema nodosum
what is bloody diarrhea generally associated with?
bacterial invasion and is caused by only a minority of campylobacter strains
what is enteric fever?
systemic infection that is associated with abdominal pain and fever- non-specific
when does enteric fever occur?
when bacteria proliferate within the lamina propria and mesenteric lymph nodes
what patients are at more of a risk of getting reactive arthritis when infected with campylobacter infection?
patients with HLA-B27 genotype
what is guillain-barre syndrome?
acute inflammatory demyelinating polyneuropathy; an ascending process
what is erythema nodosum?
a type of skin inflammation that is located in a part of the fatty layer of the skin
how does erythema nodosum typically present?
reddish, painful, tender lumps most commonly located in the front of the legs below the knees
what are the characteristics of shigella?
they are gram-negative unencapsulated, nonmotile, facultative anaerobes that belong to the Enterobacteriaceae family and are closely related to enteroinvasive E. coli
what is the most common causes of bloody diarrhea worldwide?
shigella
who is at risk for getting infected with shigella?
in the US and europe- children in daycare centers, migrant workers, travelers to low resource countries, and individuals in nursing homes
who is at risk of death associated with shigella?
deaths are generally limited to children younger than 5 years of age
where is shigella endemic?
in countries with poor sanitation
in what part of the GI tract does shigella most commonly infect?
shigella infections are most prominent in the left colon, but the ileum may also be involved, perhaps reflecting the abundance of M cells in the dome epithelium overlying Peyer patches
what is the histology like in cases of shigella?
because of the tropism for M cells, aphthous ulcers similar to those seen in Crohn disease may occur
what does the mucosa look like in cases of shigella?
it is hemorrhagic and ulcerated, and pseudomembranes may be present
after an incubation period of up to 1 week, what does shigella cause?
self-limited disease characterized by 7-10 days of diarrhea, fever, and abdominal pain (enteric fever)
how does shigella infection present in children?
duration of symptoms is usually shorter in children, but severity is often much greater
in adults, what is an uncommon subacute presentation of shigella?
weeks of waxing and waning diarrhea that can mimic new-onset ulcerative colitis
what does confirmation of shigella require?
stool culture
how should you treat shigella infections?
antibiotics but NOT antidiarrheal medications
what are the complications associated with shigellosis?
extra-intestinal manifestations (reactive arthropathy); shiga toxin can cause hemolytic-uremic syndrome; toxic megacolon
discuss the likelihood of becoming infected with salmonella?
very few viable salmonella are necessary to cause infection; the absence of gastric acid, in individuals with atrophic gastritis or those on acid-suppressive therapy, further reduces the required inoculum
what population of people is salmonella most common?
young children or older adults, with peak incidence in the summer and fall
what is essential for the diagnosis of salmonella?
stool cultures
what are the two types of salmonella infection?
typhoidal and non-typhoidal
what does typhoidal salmonella infection cause?
typhoid fever and paratyphoid fever
what does non-typhoidal salmonella cause?
gastroenteritis and food poisoning
infection by salmonella paratyphi is more common among what group of people?
travelers
what areas are strongly associated with salmonella typhoidal?
travel to india, mexico, philippines, pakistan, el salvador, and haiti
who is the reservoir for salmonella typhi and paratyphi?
humans
gallbladder colonization with S. typhi or S. paratyphi may be associated with what?
gallstones and a chronic carrier state
how does acute infection with salmonella typhi present?
anorexia, abdominal pain, bloating, nausea, vomiting, and bloody diarrhea; followed by a short asymptomatic phase that gives way to bacteremia and fever with flu-like symptoms; abdominal tenderness may mimic appendicitis
what does systemic dissemination of salmonella typhi cause?
extraintestinal complications including encephalopathy, meningitis, seizures, endocarditis, myocarditis, PNA, and cholecystitis
who are the at risk groups for salmonella typhi?
cancer, immunosuppression, EtOH, cardiovascular, sickle cell, hemolytic anemia patients
what skin manifestation is associated with salmonella typhi infection?
erythematous maculopapular rash (rose spots)
what are 3 species of yersinia?
enterocolitica, pseudotuberculosis, pestis
how is iron associated with yersinia?
iron enhances virulence and stimulates systemic dissemination- this explains why individuals with increased non-heme iron, such as those with certain chronic forms of anemia or hemochromatosis, are at greater risk for sepsis and death
What part of the GI tract does yersinia typically involve?
right side: ileum, appendix, and right colon
where do the yersinia organisms proliferate?
extracellularly in lymphoid tissue, resulting in regional lymph node and peyer patch hyperplasia as well as bowel wall thickening
what happens to the mucosa in yersenia infections?
the mucosa overlying lymphoid tissue may become hemorrhagic and aphthous erosions and ulcers may appear along with neutrophil infiltrates and granulomas
what is yersinia sometimes confused with?
crohn disease
what are the post yersinia infection complications?
reactive arthritis with urethritis and conjunctivitis, myocarditis, erythema nodosum, and kidney disease
what are the characteristics of escherichia coli?
they are gram-negative bacilli that colonize the healthy GI tract; most are nonpathogenic, but a subset cause human disease
what is ETEC?
enterotoxigenic- principal cause of traveler’s diarrhea
what is EHEC?
enterohemorrhagic- E. coli O157:H7 and nonOH157:H7
what is pseudomembranous colitis?
disruption of the normal colonic microbiota by antibiotics allows overgrowth of Clostridioides difficile
who is at risk for pseudomembranous colitis?
in addition to antibiotic treatment, risk factors include advanced age, hospitalization, and immunosuppression
what are pseudomembranes made up of?
an adherent layer of inflammatory cells and debris
what is specifically characteristic or indicative of pseudomembranous colitis?
pathognomonic histopathology
what is the presentation of pseudomembranous colitis?
fever, leukocytosis, abdominal pain, cramps, watery diarrhea, and dehydration
what is a potentially fatal complication associated with pseudomembranous colitis?
toxic megacolon
how is the diagnosis of pseudomembranous colitis typically made?
by detection of C. difficile toxin, rather than by culture, and supported by the characteristic histopathology
what are generally effective therapies for pseudomembranous colitis?
metronidazole and vancomycin
what is whipple disease?
a rare, multivisceral chronic disease, first described as intestinal lipodystrophy
what population of people is whipple disease most common?
in caucasian men, particularly farmers and others with occupational exposure to soil or animals
what is the clinical presentation of whipple disease?
triad of diarrhea, weight loss, and arthralgia
what are the extraintestinal symptoms associated with whipple disease that typically precede malabsorption?
arthritis, arthralgia, fever, lymphadenopathy, and neurologic, cardiac, or pulmonary disease
what is the morphologic hallmark of whipple disease?
a dense accumulation of distended, foamy, macrophages in the small intestinal lamina propria
what do the macrophages seen in whipple disease contain?
periodic acid-Schiff (PAS)- positive, diastase-resistant granules that represent partially digested bacteria within lysosomes
a similar infiltrate of foamy macrophages is present in intestinal mycobacterial infections, and the organisms are PAS-positive in both whipple disease and mycobacterial infections. How can you tell them apart?
the acid-fast stain can be helpful, since mycobacteria stain positively, while T. whippelii does not
approximately half of all gastroenteritis outbreaks worldwide are thought to be due to what?
norovirus
what is responsible for most sporadic cases of norovirus?
fecal-oral transmission
where do norovirus infections spread easily?
within schools, hospitals, nursing homes, and other large groups in close quarters, such as on cruise ships
who is especially at risk for significant infections of norovirus?
immunocompromised patients
what is rotavirus?
an encapsulated virus with a segmented, double-stranded RNA genome
who is the most vulnerable for rotavirus?
children between 6 and 24 months
where are rotavirus outbreaks common?
in hospitals and daycare centers
what is the effect of rotavirus?
the loss of absorptive function and net secretion of water and electrolytes is compounded by an osmotic diarrhea cause by the incomplete absorption of nutrients
