SFP: GI infection and malabsorption Flashcards
Describe secretory diarrhea
Intestinal cells have a net fluid secretion due to factors like viruses, infections, tumors, or toxins. This persists with fasting.
Describe osmotic diarrhea
Solutes left in the intestines cause excessive osmotic force that pulls fluid into the intestine, usually due to enzyme deficiency (like lactase), and stops with fasting.
Describe exudative diarrhea
Usually due to an inflammatory disease, often autoimmune, resulting in purulent bloody diarrhea. It continues with fasting.
Describe malabsorption diarrhea
Due to enzymatic deficiency or insufficiency that results in products not being broken down and absorbed (ex: steatorrhea). This stops with fasting.
Describe deranged motility diarrhea
Issues with gastric motility due to conditions like short bowel segments post-surgery. It varies in terms of stopping/persisting with fasting.
What defects may lead to malabsorption diseases?
Issues with pancreatic enzymes, defective bile salts, brush-border enzyme deficiencies, nutrient transport issues, and lymphatic transport issues.
What is celiac sprue?
A hypersensitivity to the gliadin portion of gluten.
What are lab findings of celiac sprue?
Anti-gliadin antibodies, anti-endomysial antibodies, and IgA antibodies to tissue transglutaminase.
What is defective in celiac sprue?
Intraluminal digestion and transepithelial transport.
What is the morphology of celiac sprue?
Loss of villi and flat mucosal lesions.
What are mutations associated with celiac sprue?
HLA-DG2 and HLA-DQ8.
What is true of mucosa in celiac sprue?
It has much higher lymphocyte content than normal intestinal mucosa, leading to damaged epithelium that causes malabsorption.
What can celiac disease increase risk for?
Anemia, adenocarcinoma, T cell lymphoma, osteoporosis.
Describe the process of celiac disease
- Gliadin component of gluten attaches to HLA-DQ2 or DQ8 on APC’s.
- APC’s present to T cells, resulting in T and B cell recruitment.
- B cells produce antibodies.
- Hypersensitivity upon introduction of gliadin in the future.
What is tropical sprue?
An enteric dysfunction similar to celiac, caused by environmental or bacterial factors. Morphology is similar but no antibodies are present.
Describe lactase deficiency
A deficiency in lactase prevents the breakdown of lactose in the small intestine, which may be congenital or acquired due to autoimmune diseases or infection.
A breath hydrogen test is used for…
Lactase deficiency.
What is abetalipoproteinemia?
Accumulation of fat in the cytoplasm due to a transport defect, preventing formation of plasma lipoproteins like chylomicrons, VLDL, and LDL.
How does abetalipoproteinemia present?
In infancy with failure to thrive, diarrhea, and steatorrhea.
Spur red cells are seen in…
Abetalipoproteinemia.
What is the presentation of microscopic colitis?
Chronic loose stool with a normal colonoscopy.
What are the two types of microscopic colitis?
Collagenous (thickened collagen layer) and lymphocytic (increased intraepithelial lymphocytes).
Which type of colitis is more associated with celiac disease?
Lymphocytic colitis.
What is graft vs host disease?
A condition in the colon after bone-marrow transplant where donor T cells attack the crypts in the large intestine mucosa.
What is the histologic feature of graft vs host disease?
Apoptotic bodies at the base of the crypts.
What is infectious enterocolitis?
Diarrhea and ulceroinflammatory changes due to a virus, bacteria, or parasite.
What is the issue with infectious enterocolitis?
If left untreated, the dehydration it causes can lead to death.
What are the possible mechanisms of bacterial enterocolitis?
Ingestion of preformed toxin, a toxigenic organism that produces an enterotoxin, or an enteroinvasive organism that invades and destroys the mucosa.
Describe cholera
A preformed enterotoxin that opens CFTR channels to draw water into the lumen of the gut, causing diarrhea.
What are histologic features of infectious enterocolitis?
Damaged epithelium and lots of neutrophils.
Describe campylobacter enterocolitis
Often seen in people traveling and may be related to reactive arthritis.
Describe shigellosis
Most common cause of bloody diarrhea, may be related to reactive arthritis, and has a low organism requirement for infection.
Describe enterotoxigenic E. coli
Transmitted fecal-orally, seen in travelers, and has a heat-labile toxin.
Describe enterohemorrhagic E. coli
Obtained from undercooked meat, milk, and vegetables. It has Shiga-like toxins.
What are the serotypes of enterohemorrhagic E. coli?
0157H7 or non-0157H7.
What causes hemolytic uremic syndrome?
Enterohemorrhagic E. coli.
Describe salmonellosis
Causes typhoid fever; may lead to rashes, anorexia, bloody diarrhea, meningitis, myocarditis, and gallbladder colonization, often contracted from contaminated food.
Describe pseudomembranous colitis
An antibiotic-associated colitis that allows for C. difficile overgrowth, leading to pseudo membrane formation (yellow plaques).
What is the histology of pseudomembranous colitis?
Neutrophils and fibrin sitting on top of the mucosa.
How do we treat C. diff?
Vancomycin.
Compare infection from preformed toxin vs enteric pathogens
Preformed toxin infections come on faster and are over quickly, while enteric pathogens have an incubation period.
What should be on a differential with Crohn’s disease?
M tuberculosis.
What is seen on histology with mycobacterial infection in the colon?
Macrophages in the stroma highlighted by acid-fast stain.
What is Whipple disease?
Condition caused by Tropheryma whippelii that causes macrophages in the lamina propria of the small bowel and dilated lymphatics, similar to M. avium but will not stain acid-fast.
What other complaints may be present with Whipple disease?
Diarrhea from malabsorption, CNS issues, CVD issues, and joint pain.
What two viruses are associated with viral gastroenteritis?
Often caused by rotavirus or norovirus.
Describe viral gastroenteritis from rotavirus
Most common cause of severe childhood diarrhea; often seen at 6-24 months.
Describe viral gastroenteritis from norovirus
Causes half of all gastroenteritis outbreaks from food-borne illness and may cause sporadic gastroenteritis from person-to-person transmission.
