week 3- gastro Flashcards
(47 cards)
• GI tests:
o Gastric Analysis o Gastro Test o Heidelberg Test o H. pylori Test o Schilling Test o D-xylose Absorption Test o Intestinal Permeability Test o Lactose Intolerance o Bacterial Overgrowth Test o Celiac Tests
• Food sensitivity tests:
o IgG/IgE
o EAV
• Barrier against stomach acid:
o Mucus, protects
o Bicarbonate, neutralizes
• gastric acidity & analysis:
o Fast 12 hrs; 24 hrs abstain: drugs, acid blockers, ETOH, caffeine
o Nasogastric (NG) tube →Fasting gastric contents aspirated
o → gastric volume, presence of blood or bile, pH, total HCL: basal acid output (BAO)
o Give Histamine or other gastric stimulant
o Specimens collected at 15 min intervals over 1-2 hrs
o Measures maximal acid output (MAO)
• Normal findings of gastric analysis:
o Fluid clear or hazy, no food, blood or bile present
o pH 1.5-3.5, fasting total acidity under 2mEq/L
o BAO w/o stimulation 0-5
o MAO w/ stimulation 10-20
• Cause ↓ or ↑stomach HCl:
o ↓: Old age, Chronic Renal Failure, Pernicious anemia, Post-vagotomy, Atrophic gastritis, Thyroid toxicosis, Adrenal insufficiency, RA, Vitiligo
o ↑: Peptic/duodenal ulcer, Zollinger-Ellison syndrome, Hyperplasia/hyperfunction of antral gastric cells, SI resection
• “string/gasgtro test”
o For gastric acidity: gastro test capsules
o weighted gelatin capsule, 70 cm absorbent pH-sensitive cotton floss
o swallow w small amount of water
o Proximal end held outside mouth, floss unwinds, stays 10 min
o Remove w rapid, gentle pull; on white paper
o distal part rubbed w pH developer stick
• results of “string/gastro test”
o ambient, unchallenged, Normal pH: under 3
o Unchallenged pH mb normal in hypochlorhydria
o Achlorhydria: ↑ pH, over 3; challenge test not required
• Bicarbonate Challenge Test:
o After string/gastro test
o 10 ml saturated NaHCO3 given by mouth, swallowed with 4 oz H2O
o After 40 mins, retest pH w Gastro test capsule
o pH under / = pre-challenge pH, w normal secretory ability
• correlation of gastric analysis and string/gastro test?
o Good, 93%, by intubation
o Reliable & relatively inexpensive method to measure gastric pH
• Heidelberg test:
o For gastric acidity
o Uses radio frequency receiver next to pt
o Capsule for internal use contains a transmitter, frequency proportional to pH
o Capsule activated before swallowing, receiver calibrated to standard pH solution
o Swallow → register ambient gastric pH
o If ambient fasting pH over 3, suggests achlorhydria, no challenge test required
o NaHCO3 challenge: like Gastro Test
• Results, dis/advantages of Heidelberg test?
o pH monitored, re-acidification time recorded
o Normal re-acidification time 12-33 mins (varies with age)
o Ad: Determine pH, re-acidification time, pH of SI
o Dis: Expensive
• Absorption test: Schilling test
o help identify megaloblastic anemia dt B12 def
o Determine mechanism of malabsorption
o fast 12 hrs prior & 3 hrs after test doses of B12 given (radioactive, 57Co)
o Dx for pernicious anemia
o not in ND scope of practice
o Oral RA B12 given alone, 1 mg loading dose normal B12 IM (binds all body’s receptor sites)
o Any RA B12 absorbed is excreted in urine
o 24 hr urine analyzed for RA B12
• Schilling test results, work-up:
o Normal: 8-40% RA B12 excreted o impaired absorption: little or no RA B12 excreted (eg Pernicious Anemia) o Abn results re-tested in 10 d o RA B12 given orally w IF o If normal, dx= Pernicious Anemia o Still ↓: give abx for 1 wk, retest o If normal: malabsortion dt dysbiosis o Still ↓: repeat RA B12 w pancreatic enzymes (neede to make B12 able to bind to IF) o Retest urine, observe for ↑ RA B12
• Dx’s based on schilling test results:
o Pernicious anemia: ↓ 58Co, N w IF, ↓ w Panc Enz, ↓ after 5 d abx
o Chronic pancreatitis: ↓ 58Co, ↓ w IF, N w PE, ↓ w abx
o Bacterial overgrowth: ↓ 58Co, ↓ w IF, ↓ w PE, N w abx
o Ileal dz: ↓ 58Co, ↓ w IF, ↓ w PE, ↓ w abx
• IF blocking AB:
o =auto-Ab
o Replaces Schillign test for Pernicious Anemia.
o If serum B12 under 300 pg/ml, test for Methylmalonic Acid (MMA)
o If ↑ MMA, test for IFBA
• H. pylori:
o S or C shaped g(-) bacteria
o Major cause of active chronic gastritis
o role in development of duodenal (90%), gastric (70%) ulcers
o gastric CA: 6x risk w H pylori infx
o cultured when collected during endoscopy (bx) or by a string test. 7-10 d
o Sero test sensitive to IgA, IgM, IgG Abs to H. pylori
o Radio labeled carbon breath test
o Stool Ag test highly sensitive and specific
• Defense mechanism of h pylori:
o Covered in mucus, fights stomach acid w enzyme urease
o Urea (from saliva, gastric juice) → HCO3 & NH3 (strong bases)
o = neutralize, protect from stomach acid
o Dx w breath test
• H pylori breath test:
o drink radio labeled urea (13C)
o H. pylori metabolizes urea rapidly, labeled carbon absorbed
o measured as CO2 in pt’s expired breath
o Sensitivity and specificity 94-98%
• H pylori serum test:
o ↑ IgG (Chronic) titers may indicate active or past infx; ↑ 2 mos post exposure, peak ~ 60 d; After successful eradication, may remain ↑ up to 1 yr
o IgA ↑ 2 mos after infx, ↓ 3-4 wks after tx
o IgM (Acute) ↑ 3-4 wks after infx, gone 2-3 mos after tx (not good indicator)
• H pylori test from bx:
o During endoscopy, get bx of stomach and duodenum
o Bx urease test: rapid testing at time of bx
o Histological ID (gold standard)
o Culture → susceptibility testing.
• H pylori stool ag vs urea breath test:
o Dx: not affected by meds; off PPIs for 1 wk
o Monitor FDA cleared for therapeutic monitoring; PPI’s may interfere
o Test for cure: 1 wk, meds don’t interfere; 4 wks, no meds
o Cross reactivity: none; other urea producers may interfere
o Peds: indicated; not indicated
o Special equip: none; Mass or IR spec
o Accuracy: bot excellent
o Yuck factor: stool!; drink C13 solution
o Stability of specimen: 1-2 d at RT; 7 d
• Ssx of malabsorption:
o Weight loss (even w ↑ Cal), fatigue o Diarrhea: bulky, oily (fat), liquid (carbs) o Excess flatus o Fe/B vits: glossitis, cheilosis o Zn: acrodermatitis o EFAs: dry skin and hair o IDA: microcytic anemia o folate/B12: macrocytic anemia o Vit D/Ca: osteopenia/osteoporosis o Vit A: night blindness o Vit K: easy bruising
• Tests for Carb malabsorption:
o D-xylose:
o Lactose (in)tolerance: oral 50 g lactose, blood glucose at 0, 60, 120 mins. ↑ over 20 mg/dL plus development of symptoms is dx
o Breath tests: H2, 14CO2, 13CO2; lactose, fructose, sucrose, isomaltase and others)
