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101 Cards in this Set

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MALABSORPTION - ZHANG - FRIDAY FEB 9
what was said about the etiology of generalized malabsorption?
may be multifactorial - one pathway impacts another - impairment of multiple nutrient classes resulting in full blown malabsorption syndrome
what is the most common clinical presentation of malabsorption?
chronic diarrhea
what is steatorrhea like in color and consistency?
bulky, greasy, yellow-gray stool (foul-smelling)
what are other non-abdominal symptoms of malabsorption (list)?
anemia, muscle wasting, generalized edema, hypoglycemia, tetany, osteopenia, peripheral neuropathy, bleeding tendency, skin changes, glossitis
MAJOR MALABSORPTION SYNDROMES - CELIAC DISEASE
what are other names for celiac disease (3)?
1) celiac sprue; 2) gluten-sensitive enteropathy; 3) non-tropical sprue
what is this chronic disease characerized by, in what part of the GIT, and what does this lead to?
characerized by mucosal changes (villous atrophy) in the SI, leading to impaired nutrient absorption
what causes improvement of this disease?
withdrawal of grain products from diet
what is the prevalence?
1% of population
what is the hallmark of celiac disease?
T-cell mediated chronic inflammatory reaction
what is gluten?
a gliadin complex of what or closely related grains
what are factors that lead to celiac disease (3)?
1) genetic; 2) host immune response; 3) environmental factors
where do gluten-sensitive cells accumulate, and what type of cells accumulate there?
in the small bowel mucosa there is accumulation of: 1) intraepithelial CD8+ T cells; 2) large number of lamina propria CD4+ T cells
what happens to villi?
atrophy or total loss
what happens to crypts?
elongated with inreased mitotic figures
where are chronic inflammatory cells increased?
lamina propria
where in the bowel are changes most pronounced?
in proximal small bowel
is malabsorption selective or non-selective?
non-selective
at what ages does this disease present (2)?
1) infancy; 2) fifth decade
what symptoms occur in infants (2)?
1) failure to thrive; 2) symptomatic diarrhea
what are presenting symptoms in adults (besides diarrhea/weight loss/fatigue/flatulence) (2)?
1) dermatitis herpetiformis; 2) neurologic disorders
how is diagnosis of celiac disease made (3)?
1) clinical documentation of malabsorption; 2) small bowel bipsy changes; 3) improvement with dietary changes
what type of test is done for screening/follow up?
serologic test
what is response to treatment like?
good
what is there a long-term risk for (2)?
1) lymphoma; 2) small intestinal adenocarcinoma
TROPICAL SPRUE (POST-INFECTIOUS SPRUE)
what is this disease like, and who gets it?
like celiac disease, occurs in patients living in or visiting tropics
what etiologic agent is responsible?
presumed infectious etiology - no specific etiology has been identified, but noted in association with bacterial overgrowth of enterotoxigenic organisms
what does malabsortpion follow, and how long after?
begins within days to weeks of acute diarrheal infection, and may persist if untreated
what specific deficiencies may the patient have (2)?
1) B12; 2) folate
what is morphology like, and where in the bowel does it occur?
variable - normal to severe diffuse enteritis, seen at all levels of small bowel
what is the treatment, and how effective is it?
complete recovery after treatment with broad spectrum antibiotics
WHIPPLE'S DISEASE
what is the cause of Whipple's disease?
rare systemic condition due to a bacterial infection by Tropheryma whippelii, a gram positive actinomycete
when in life, and in what sex, does it present?
usually presents in adult life (30-40's), predominantly seen in white males
what areas does Whipple's disease primarily affect (3)?
1) GIT; 2) CNS; 3) joints; can affect any organ system
what are symptoms besides malabsorption/diarrhea/weight loss (2)?
1) fever; 2) arthritis
what is seen morphologically in the small intestine?
large macrophages filling and expanding in the lamina propria
are edema and/or inflammation present?
may be edema, but no inflammation
what is seen in the macrophage cytoplasm?
PAS + granules
what other area is involved in Whipple's disease?
lymph nodes, with lymphatic obstruction
what is seen on the EM, and where?
rod-shaped bacilli (intra- and extracellular)
what is the treatment, and how well does it work?
antibiotic therapy - often prompt response, but some patients have protracted disease course
DISACCHARIDASE (LACTASE) DEFICIENCY
where is lactase found?
in the apical cell membrane of villous absorptive epithelial cells
what does incomplete breakdown of lactose lead to?
osmotic diarrhea from unabsorbed lactose
in what race is there a high incidence?
African Americans
what form of this disease is rare, and what is it like?
congenital - rare, babies - explosive watery, frothy stools and abdominal distention with milk feedings
what is the acquired form thought to develop from?
viral or bacterial enteric infecitons
what changes will be seen on EM and histology?
none
what is the treatment?
dietary restriction
ABETALIPOPROTEINEMIA
how is this disease inherited, and what type of disease is it?
rare autosomal recessive inborn error of metabolism
what can't patients synthesize?
synthesize apolipoprotein B
what does this cause problems with?
synthesis and export of lipoproteins from intestinal mucosal cells
what happens to dietary fat?
it is hydrolyzed and enters absorptive cell, and is re-esterified, but cannot form chylomicrons because of lack of apolipoprotein B
what happens to triglycerides in epithelial cells?
they are stored as lipid vacuoles
what lipoproteins will be absent from the plasma (3)?
CM, VLDL, and LDL - all those containing apolipoprotein B
what was one of the systemic abnormalities mentioned to be caused by failure to absorb certain essential fatty acids?
lipid membrane - RBC's - acanthocytes
what is microscopy and morphology like?
microscopically and morphology overall normal, with only lipid vacuoles, that may be highlighted with a fat stain
what are symptoms seen in infancy (besides diarrhea/failure to thrive)?
1) neurologic symptoms; 2) steatorrhea
BACTERIAL OVERGROWTH SYNDROME
how many organisms are normally in the SI and why?
few, because of gastric acidity, sweeping action of motility, and secretion of intestinal immunoglobulins
what can bacterial overgrowth directly cause (3) that lead to malabsorption?
1) deconjugation of bile salts; 2) direct injury to mucosal cells by bacteria; 3) direct utilization of nutrients by bacteria
what can bacterial overgrowth result from (3)?
1) blind loop syndrome; 2) multiple diverticula; 3) abnormal motility (muscular/neurogenic defects)
what is the treatment?
antibiotics
what does microsopy depend on?
etiology of overgrowth
LABORATORY TESTS
what are two important tests we must know?
1) D-xylose tolerance test; 2) fecal fat test
what does the absorption of D-xylose reflect, and what is the rationale?
the integrity of carbohydrate absorption by the SI, because no enzymatic digestion is required prior to absorption
what two things does it help distinguish between, and what test value is obtained in each?
distinguishes between proximal SI malabsorption (low test value) from pancreatic steatorrhea (normal test value)
how is this test performed?
D-xylose is given orally, then D-xylose level in a 5-hr urine sample is measured - if level is low, then this is consistent with proximal SI malabsorption
what type of measurements can be taken in the fecal fat test?
qualitative, quantitative
how is microscopic exam performed?
Sudan stain on random stool sample checks for presence of fat droplets and undigested muscle fibers
how is qualitative screning done, and what result indicates steatorrhea?
random stool specimen is colelcted on diet of >60 grams of fat daily, if more than 4 grams of fat = steatorrhea
how is quantitative fecal fat testing done?
3 day stool sample, collected on diet of 60-100 grams of daily fat - if more than 7 grams per 24 hours = steatorrhea
what are other laboratory tests done (list)?
peripheral blood smear, serum folate and B12, Schilling test, serum albumin, serum calcium, serum carotene, blood glucose, prothrombin time, jejunal mucosal biopsy, X-ray studies
what disease state(s) result in abnormality of the controlled delivery of gastric contents into the duodenum and subsequent release of pancreatic enzymes and bile?
surgery (gastrojejunostomy) - dumping syndrome
what disease state(s) result in abnormality of the secretion of pancreatic enzymes (amylase, lipase) into the duodenum (3)?
1) pancreatitis; 2) duct obstruction; 3) CF
what disease state(s) result in abnormality of the normal supply of bile into the duodenum (2)?
1) hepatobiliary dysfunction; 2) stones
what disease state(s) result in abnormality of the normal enterohepatic circulation of bile salts (4)?
1) bacterial overgrowth; 2) surgical excision; 3) Crohn's disease; 4) lymphoma
what disease state(s) result in abnormality of the absorption interface of enterocyte / microvilli and glycocalyx (3)?
1) lactose intolerance; 2) celiac disease; 3) Whipple's disease
what disease state(s) result in abnormality of the absorptive surface area from enterocyte damage (decrease in metabolic function - list)?
resection, fistulas, celiac disease, Whipple's disease, radioation, abetalipoproteinemia, Crohn's disease
what disease state(s) result in abnormality of the transportation of nutrients from intestinal epithelial cell through intestinal wall by capillaries and lymphatics (3)?
1) Whipple's disease; 2) lymphoma; 3) congenital lymphangiectasia