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