Term
| how is gastric acid output measured? |
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Definition
| gastric aspiration, collection obtained every 15 mins (first hour = basal acid output). then stimulant given (another hour, 15-minute collections --> maximal acid output); women and elderly have decreased BAO and MAO. normal values range is broad, overlaps with pathological values. BAO <5 mEq/h; avg MAO 20 mEq/h upper limit of 40. |
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Term
| achlorhydria is defined as? |
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Definition
| failure of pH of gastric secretion to fall below 6 during stimulated collection |
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Term
| how is gastric cancer diagnosed? |
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Definition
| achlorhydria after stimulation (gastric output test) in a patient with a gastric ulcer almost always indicates gastric carcinoma. nowadays we use radiologic and fiberoptic gastroscopy with biopsy and cytological studies. |
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Term
| what are the major indications for serum gastrin measurement? |
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Definition
| possible ZES or pernicious anemia |
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Term
| describe the 2 etiologies of ZES |
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Definition
| 2/3 sporadic (w/o fam hx) --> usually single lesion; 1/2 associated MEN-1 (multiple endocrine neoplasm syndrome) --> multifocal gastrinomas (and tumors elsewhere, 3P - pancreas, pituitary, parathyroid) |
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Term
| normal fasting serum gastrin level? |
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Definition
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Term
| what is the urea breath test used for? how does it work? |
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Definition
| used to detect H.pylori and to check for the adequacy of antibiotic rx against h.pylori, test 1 month after antibiotic regimen stopped. test solution of urea labeled with c14 or c13 --> bacteria present? --> will hydrolyze the urea, release ammonia and isotypically labeled CO2 --> CO2 extracted and measured --> presence of the labled isotopes in exhaled CO2 indicates that urea has been hydrolyzed by bacterial urease! |
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Term
| what can cause a false + in the UBT test? |
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Definition
| presence of other urease producing bacteria (i.e. proteus mirabellis) |
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Term
| what might cause a false negative in the UBT test? |
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Definition
| incidental use of proton pump inhibitors, antibiotics, or bismuth containing antacids |
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Term
| what is the serum antibody assay (ELISA) against h.pylori useful in? |
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Definition
| detecting prior exposure to h.pylori. cannot distinguish past from current infection. negative test can exclude h.pylori but positive test must be followed with UBT |
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Term
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Definition
| bx specimen obtained from endoscopy --> placed into fluids or gels containing urea --> urease splits urea producing ammonia --> change in pH affects color indicator |
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Term
| what is the gold standard for dx of h.pylori? |
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Definition
| BX! histologic examination + staining. H&E stain --> inflammatory exudate. SILVER STAIN --> curved, rod-shaped organism, PCR testing to confirm |
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Term
| elevated serum urea nitrogen in a patient who had previously recent normal urea nitrogen or serum creatinine suggests? |
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Definition
| upper GI bleed! digestion of blood proteins in the small intestine and absorption of nitrogenous products may be the cause (although, usually rise in urea nitrogen d/t hypovolemia of acute blood loss) |
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Term
| describe how the fecal occult blood test works |
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Definition
| peroxidase activity of hemoglobin. normal person loses 2-2.5 mL of blood in GI tract daily (normal shedding of epithelial cells) --> occult tests used to detect blood loss greater than 5-10mL per day |
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Term
| what things can cause a false + in guiac tests? |
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Definition
| digital rectal exam can cause injury to rectal mucosa; peroxidase activity of other fecal constituents - myoglobin and hb of ingested meat, fish; bacteria in bowel, horseradish, turnips, banana, black grapes, pears, plums have peroxidase activity |
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Term
| what things can cause a false negative |
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Definition
| large amounts of vitamin C and other antioxidants |
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Term
| what sort of test has been made to eliminate the false + d/t extraneous peroxidase activity? |
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Definition
| immunochemical tests, using antibodies to glbin. more sensitive and specific, but no use in testing for upper GI bleed bc globins are destroyed in the sm. intestine |
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Term
| describe the apt test (indications, methods) |
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Definition
| indicated for newborns who have bloody stools passed on the 2nd or 3rd day of life to determine the source. need to distinguish between maternal blood swallowed during delivery (or from nipple fissure) from newborn GI hemorrhage. infant blood contains HbF, which is alkali resistant! test on feces or vomit. |
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Term
| what findings are sufficient for a presumptive diagnosis of celiac disease? what is neded for definitive dx? |
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Definition
| positive serological tests + bowel bx (or skin bx-proven dermatitis herpetiformis); definitive dx need to demonstrate resolution of sx after gluten-free diet |
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Term
| what is testing for antigliadin antibodies useful for? |
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Definition
| monitoring adherence to gluten-free diet; no longer recommended as routine screening test for celiac |
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Term
| what antibody is highly sensitive and specific for celiac disease? what should we be aware of before performing the test? |
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Definition
| tTGase IgA antibody (sensitive, easy to perform, more reproducible); common problem: celiac patients are IgA deficient --> false negative serological test. if this is the case, test for IgG antibody studies instead |
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Term
| what are the 2 forms of gluten sensitive enteropathy? what bx findings and antibodies do we expect? |
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Definition
| celiac disease and dermatitis herpetiformis; expect villous atrophy from endoscopically obtained small bowel bx; IgA endomyseal abs, IgA anti-gliadin abs, RI anti-reticulin abs; IgA endomysesal antibodies will disappear when adhering to gluten-free diet |
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Term
| 2 ways to test for dissacharidase deficiencies? |
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Definition
| intestinal bx --> measure dissacharidase activities in intestinal homogenates; oral lactose tolerance tests, measuring increase in plasma glucose or galactose following ingestion of lactose |
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Term
| how do we check for bacterial overgrowth of the small intestine? (2 ways) |
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Definition
| prox small intestine usually contains few bacteria; intubation of jejunal contents --> demonstration of bacterial counts >10^7 organisms/mL and anaerobes >10^4 is diagnostic. also use hydrogen breath test using lactulose or glucose. |
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Term
| how do we check for bile salt malabsorption? and what conditions do we expect this malabsorption? |
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Definition
| give synthetic radioactive bile acids. bile salt malabsorption following ileal disease, after cholecystectomy, IBS |
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Term
| when is a test for protein-losing enteropathy indicated? |
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Definition
| +hypoalbuminemia; renal loss, liver disease and malnutrition excluded. |
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Term
| what are 2 tests that can be used to check for protein-losing enteropathy? |
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Definition
| measurement of fecal 15Cr-albumin following IV injection. also, fecal clearance of alpha-1-antitrypsin |
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Term
| what does the schilling test determine? |
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Definition
| absorption of vitamin b12 |
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Term
| what are the 3 major pathological causes for increase in fecal fat? |
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Definition
| impairment of intestinal absorption; deficiency of pancreatic enzymes; deficiency of bile |
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Term
| increases in fecal fat in following diseases: |
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Definition
| celiac, crohns, whipples, cystic fibrosis, sprue, atrophy of malnutrition |
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Term
| how do we test for fecal fat? |
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Definition
| microscopic bx using fat stain; 48-96 hour stool sample --> steatorrhea defined as >5g lipid (as fA) in feces per 24 hrs |
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Term
| what is the d-xylose test used for? how does it work? |
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Definition
| used in ddx of steatorrhea, normally absorbed in the jejunum. if the test is abn --> jejunal dysfunction. test wnl --> should evaluate bile salt deficiency, terminal ileal disease, or pancreatic func |
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Term
| what is factitious diarrhea and how do we test for it? |
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Definition
| surreptitious laxative abuse; test with analysis of stool water osmolality/electrolytes. normal stool osmolality 290 mOsm/kg; calculate osmotic gap (290 - [2x sodium+potassium]) --> >125 --> magnesium laxative should be suspected (maalox) |
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Term
| what does the presence of reducing substances in the stool indicate? |
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Definition
| carbohydrate malabsorption |
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Term
| what would cause leukocytes in the stool? |
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Definition
| (>3 neutrophils per hpf) in conditions that affect the intestinal wall (UC, invasive bacterial pathogen); viruses and parasites do not cause leukocytes |
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Term
| meat fibers in stool indicates |
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Definition
| impaired intraluminal digestion; biliary obstruction or pancreatic exocrine function |
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Term
| carcinoembryonal antigen levels useful for? |
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Definition
| monitoring patients for tumor recurrance and therapeutic efficacy, levels fall following successful tx and rising levels indicate recurrance |
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Term
| anti-saccharomyces cerevisae antibody + -->? |
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Definition
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Term
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Definition
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