Tests for gastric, duodenal secretions


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  • Histalog = ametazole, betazole hydrochloride
  • IRT level is elevated, an infant may have cystic fibrosis; an infant or adult may have abnormal pancreatic enzyme production, pancreatitis, or pancreatic cancer; or the elevated IRT may be a false positive. Elevated levels need to be followed with further testing.
  • Tests for gastric, duodenal secretions

    1. 1. MV GASATAYA, M.D.
    2. 2. Gastric Secretions • The mucous membrane of the stomach has tubular gastric glands that secrete: 1. Hydrochloric acid • From the parietal cells • Needed to convert pepsinogen to pepsin •Hydrolyze polypeptides and disaccharides directly 2. Mucus • From the goblet cells and the mucous glands • Protective to stomach wall •Complex mixture of mucoproteins and mucopolysaccharides 3. Intrinsic factor • From the parietal cells • Is required for vitamin B12 absorption 2
    3. 3. Gastric secretions – cont. 4. Electrolytes - gastric secretion contains all the electrolytes found in other body fluids in a combined osmolar concentration equal to or slightly greater than plasma. 5. Digestive Enzymes PEPSIN – major digestive enzyme of gastric secretion - secreted by chief/peptic cells as 2 proenzymes: pepsinogen and zymogen (activated by gastric acid) - catalyzes degradation of proteins to proteases and peptones
    4. 4. OTHER DIGESTIVE ENZYMES (GASTRIC) - Gastric lipase = digestion of dietary fat - renin (chymosin) = secreted by chief cells - gastricsin (pepsinogen C) 6. Non-Digestive Enzymes: LDH, aspartate amino transferase, isocitric dehydrogenase, alkaline phosphatase
    5. 5. Secretions of the Small Intestine • In addition to mucous-secreting goblet cells, there are many specialized mucous-secreting glands (Brunner’s glands) that secrete a thick, alkaline mucus in response to certain stimuli • Enzymes in the membranes of the microvilli include: • Peptidase – breaks down peptides into amino acids • Sucrase, maltase, lactase – break down disaccharides into monosaccharides • Lipase – breaks down fats into fatty acids and glycerol • Enterokinase – converts trypsinogen to trypsin • Somatostatin – hormone that inhibits acid secretion by stomach • Cholecystokinin – hormone that inhibits gastric glands, stimulates pancreas to release enzymes in pancreatic juice, and stimulates the gallbladder to release bile • Secretin – stimulates the pancreas to release bicarbonate ions in pancreatic juice 6
    6. 6. Examination of Gastric Contents  1. To determine if the patient can secrete gastric acid  2. To measure the amt. of acid produced by a patient with symptoms of peptic ulcer  3. To support a hypersecretory state characteristic of Zollinger-Ellison syndrome  4. To determine the completeness of vagotomy  5. To aid in the differential diagnosis of gastric ulcer from duodenal ulcer Summary: to evaluate the possibility of hyperchlorhydria or hypochlorhydric states.
    7. 7. ADDITIONAL PROCEDURES NOW IN USE FOR THE DETECTION OF THESE DISORDERS  1. Direct examination of lesion by endoscopy  2. Improved radiologic techniques – air contrast  3. pH sensitive electrodes that will transmit pH readings when passed into the stomach  4. measurement of serum gastrin levels  5. cytologic exam of gastric contents for malignant cells  6. immunologic testing of serum for the precense of antiintrinsic factor and antiparietal cell antibodies seen in pernicious anemia
    8. 8. SPECIMEN COLLECTION  By nasal or oral intubation of the Px. A Levin Tube is passed thru the nose or a Rehfuss or similar tube is passed thru the mouth. Performed in a fasting state.  To ensure complete collection, position of the tube is checked by flouroscopic examination of the stomach  Px. Should be instructed not to swallow excessive amounts of saliva during collection since it would neutralize gastric acidity  Acidity testing is routinely performed on 15-min. interval specimens. Aspirate placed in time labeled containers that represent each 15 min of the required collection period & not as a single specimen.
    9. 9. ROUTINE GASTRIC ANALYSIS 1. PHYSICAL APPEARANCE - normal fasting gastric secretion is pale gray, translucent, slightly viscous fluid with a fairly pungent odor. - after a 12-hr. fast-presence of food particles is abnormal & indicates delayed gastric emptying, often a result of pyloric obstruction - large amounts of bile produces a yellow green aspirate - blood = from other gastric lesions: gastritis, ulcer, CA or can be from lesions in mouth, nasopharynx or respi tract
    10. 10. -if bld is present, confirm by orthotoluidine or guaic tests - Gastroccult = a guaic based slide test specifically designed for detecting occult blood in gastric secretions 2. VOLUME - measured in ml. & is used with titrable acidity to determine total acid output. Volume should increase following gastric stimulation. 3. pH - pH meter used and correlation with the titrable acidity values - Anacidity =failure to produce pH less than 6.0 following gastric stimulation
    11. 11. 4. TITRABLE ACIDITY - currently the measurement of overall H+ conc. is the recommended procedure - both the ionized & un-ionized hydrogen are measured simultaneously by titrating the specimen with 0.1 N NaOH to pH 7.0 - using the indicator phenol red, which changes from yellow to red in the pH range of 6.6 to 8.0 - titration results are reported as milliequivqlents or millimoles per liter of titratable acid - milliequivalents/L of titratable acid are calculated
    12. 12. EXAMPLE: Calculate the milliequivalents/L of titrable acid in a 20 ml specimen when 2.0 ml. of 0.1N NaOH are used to reach pH 7.0 (x=mEq/L of titrable acid in 20 ml specimen) (0.1N NaOH)(2 ml.) = (x)(20 ml.) 0.2 = 20x x = 0.2 = 0.01 equivalents/L* 20 1N = equiv/L 1 equiv = 1000 mEq x = 0.01 x 1000 x = 10 mEq/L of titratable acid
    13. 13. Because titrable acidity represents mEq or mmol/L and the typical gastric secretion specimen is of considerably less volume, it also becomes necessary to calculate the ACTUAL ACID OUTPUT. ACTUAL ACID OUTPUT = specimen volume in liters X titrable acidity EXAMPLE: The first 15-min. specimen of a 1 hr. basal collection has a volume of 25 ml. To titrate 10 ml. of this specimen to the end point of phenol red, 5 ml. of 0.1N naOH is used. Calculate the: A) Titrable acidity B) acid output of the patient
    14. 14. A. (0.1N NaOH )(5 ml. ) = x(10 ml.) 0.5 = 10x x = 0.5 = 0.05 equiv./L 10 (0.05 equiv./L)(1000) = 50 mEq/L (titratable acidity) B. 25 ml x 50 = 1.25 mEq /L (acid output) 1000
    15. 15. BASAL GASTRIC ACIDITY  Basal Gastric Specimen is a 1-hr. collection, usually consisting of four 15-min fasting specimens  The volume, pH, titrable acidity and acid output of the sample that constitute the basal specimen are determined  Normal values for volume and acidity are based on the total 1 hour specimen, so individual sample results must be combined to provide the 1-hr. interval  BASAL ACID OUTPUT is the sum of all the acid outputs of the four 15-min basal samples
    16. 16.  In general, the normal basal secretion has a volume of about 30-60 ml. & contains a low acid output of approx. 1 to 4 mEq/hr. Major Diagnostic Value: markedly elevated acidity = indicative of ZollingerEllison Syndrome (condition of hypersecretion of gastric acid due to a gastrin-secreting tumor of the pancreas)
    17. 17. POST STIMULATION GASTRIC ACIDITY  Inability to produce gastric acid cannot be determined just from the analysis of basal gastric secretion alone  Need to perform post-stimulation gastric acidity tests which utilize the principle of introducing a gastric stimulant into the patient ff. the basal collection.  The stimulant of choice = PENTAGASTRIN – a synthetic compound resembling gastrin & does not cause the patient discomfort that occurs with histamine administration. Pentagastrin produces a more rapid response than histalog. (subQ = 6ug/kg body weight)
    18. 18.  When pentagastrin or histamine is used as a stimulant specimens are collected at 15-min. intervals for 1 hr. following the injection.  All post-stimulation specimens are analyzed in the same manner as the Basal specimen by measuring volume, pH, titrable acidity & calculating the actual acid output.  The hourly acid output is calculated and is now referred as the MAXIMUM ACID OUTPUT.  The PEAK ACID OUTPUT which is considered more reproducible by some laboratories is also determiend by taking the total of the two-highest 15-min acid outputs and multiplying this figure by 2 to arrive at the hourly acid output.
    19. 19. EXAMPLE Acid ouputs in mEq/L Stimulated specimen #1 = 1.95 2 = 6.0 highest 3 = 6.2 4 = 4.5 Peak Acid Output = 6.0 + 6.2 = 12.2 X 2 = 24.4 mEq/hr -using pentagastrin, the peak acidity is usually seen within 15-45 min. post injection -normal values are again variable. However, normal individuals will usually not produce a maximum acid output over 40 mEq.
    20. 20.  Normal individuals will exhibit a fall in pH to below 3.5 Hourly basal & maximum outputs that are representative of conditions that produce abnormal gastric acidity are provided in the table: condition Basal acid output (mEq/hr) Maximum acid output (mEq/hr) BAO/MAO 2.5 25.0 10% 0 0 0 Duodenal ulcer 5.0 30.0 17% Zollinger-Ellison Syndrome 18.0 25.0 72% Normal Pernicious anemia
    21. 21. MICROSCOPIC EXAM. OF GASTRIC CONTENTS Structures seen in the normal stomach: = erythrocytes, leukocytes, epithelial cells, yeast, bacteria, & particles of mucus Cellular elements are usually in various stages of autolysis so difficult to identify -Erythrocytes=in small amounts – of no consequence -Leukocytes=can be of gastric origin or from swallowed secretions. Increased numbers can result from inflammation of gastric mucousa, mouth or URT. -Epithelial cells : Squamous cells – can be dislodged from mouth, nose, pharynx or esophagus Columnar cells- significant increase in gastritis
    22. 22.  Mycobactrial species = in pulmonary TB  Heliobacter (Campylobacter) pylori – antral gastritis with gastric and duodenal ulcerations. H. pylori is charac. found in or under the mucus layer of enterocytes.  Yeasts = large numbers in the retention of gastic contents, such as pyloric obstruction  G. lamblia trophocytes or cysts, Strongyloides larvae or ascaris or hookworm ova can also be found
    23. 23. INSULIN HYPOGLYCEMIA TEST  Hypoglycemia resulting from administration of insulin is a potent stimulus to gastric secretion  Major component of stimulus is transmitted by the vagus nerves & this can be abolished by vagotomy  Valid only if the blood glucose falls below 50 mg/dl at some point in the test = usually after 30 min of insulin administration  Vagotomy is complete if the acid output in the greater of the 2 post-insulin hours is less than the greater of the 2 basal hour
    24. 24.  Incomplete vagotomy = if the acid output in the 2 hr. post insulin period exceeds that of the 2 hr. basal period by more than 0.5 mEq OR if there is an acid output greater than 2 mEq in either basal hr. TECHNIQUE: 1. Intubation of patient after a 12-hr. overnight fast. A 2-hr. basal secretion is obtained in 15-min. samples. 2. Blood sample for glucose determination is taken upon completion of the basal secretion study & at 30, 60 & 90 min. after insulin injection.
    25. 25. 3. Insulin is administered intravenously either at a fixed dosage of 15 or 20 units or at a calculated dosage of 0.20 units/kg. body weight. It is essential that a 50 ml. syringe filled with 50% (w/v) glucose solution be readily available for IV injection 4. Gastric secretion is collected in 15 min. samples for 2 hrs. after insulin injection. 5. For each basal and post-insulin gastric sample = determine the volume, titrable acidity & acid output.
    26. 26. TUBELESS GASTRIC ANALYSIS  Use of an orally administered ion-exchange resin to detect the presence of H+ in gastric fluid  Marketed under the trade name, DIAGNEX BLUE  Based on the use of a carboxyl-acid cationic resin (amberlite XE-96) with an innocuous indicator dye, Azure A coupled to it.  H+ in gastric secretion combined with the resin & liberate azure-A ions, which are then absorbed into the bloodstream in the small intestine and subsequently excreted in the urine.
    27. 27. - In principle, the presence of H+ in the gastric fluid can be determined by an estimate of the urine Azure A - Caffeine sodium benzoate was used as a gastric stimuant - Many sources of false (+) and false (-) and quantification of gastric acid is not possible
    28. 28. Indications for Endoscopy Evaluation of: 1. Abdominal pain 2. Dyspepsia 3. Dysphagia 4. Gastric outlet obstruction
    29. 29. Contraindications of Upper Endoscopy (Absolute) 1. Acute myocardial infarction 2. Acute shock 3. Atlantoaxial subluxation 4. Perforated ulcer, acute 5. Seizures
    30. 30. Relative contradictions for upper endoscopy 1. Coagulopathy 2. Prothrombin time >3 seconds over control 3. Platelet count <100,000/microliter 4. Bleeding time less than 10 min 5. Coma, unless patient is intubated 6. Myocardial ischemia 7. Thoracic aortic aneurysm 8. Uncooperativeness 9. Zenker’s diverticulum
    31. 31. COMPOSITION OF DUODENAL CONTENTS  1. Endocrine Pancreatic Secretions  2. Bile  3. Intestinal Secretion (Succus entericus) mixed with gastric secretion Pancreatic Exocrine Secretion (Major contributor to duodenal contents) =exceeds 1,500 ml per day in normal adult =colorless, clear, non-viscid, alkaline solution (pH aprox. 8)
    32. 32. PANCREATIC EXOCRINE SECRETION  Consists of: 1. 1 to 2% ORGANIC MATERIAL, mostly enzymes or their precursors (Trypsinogen, chymotrypsinogen, amylase, lipase, lecithinase, elastase, collagenase, leucine aminopepetidase & various esterases) 2. 1% INORGNIC MATERIAL Sodium = major cation Bicarbonate = major anion Na+ & K+ are present in the same conc. in serum while Ca++ & Mg+ are present in lower concentration
    33. 33.  The HCO3 conc. varies directly with the rate of pancreatic secretion, while chloride varies inversely with the rate of secretion, so that the sum of these 2 ions remain constant. STIMULI TO PANCREATIC EXOCRINE SECRETION 1. Vagal Stimulus – relatively slight & results in a small vol. of secretion that is rich in enzymes. 2. Hormonal Stimuli (2 subst. secreted by duodenal mucousa) A. Secretin = HCl stimulates its release and results in a copious flow of pancreatic secretion that is low in enzyme content & high in HCO3. B. Pancreozymin = (Cholecystokinin) stimulate the pancreas to secrete enzymes *Gastrin = weak stimulus but may cause pancreatic exocrine secretion
    34. 34. BILE  Approx. 500-1000 ml. enters the duodenum daily  usually alkaline (pH 7.0-8.5), color:yellow to brown/green  Contains bile salts (chiefly sodium glycholate & taurocholate), billirubin pigments, cholesterol, phospholipids, various inorganic salts.  Alkaline phosphatase = only enzyme present in significant amount but no function in digestion.
    35. 35. SUCCUS ENTERICUS  daily volume is not known  Contains a variety of digestive enzymes that are capable of breaking down ingested foods but enzymatic activities are considered to be relatively weak COLLECTION OF FLUID Done by duodenal intubation in the fasting state using: 1. a double lumen tube (Diamond or Dreiling tube) 2. a three lumen tube 3. certain types of instruments for small bowel biopsies = tube is equipped with a radiopaque tip thus position can be verified flouroscopically
    36. 36. MACROSCOPIC EXAMINATION: - In the fasting state, the residual content of the duodenum varies up to 20 ml. - Fluid is transparent or slightly translucent, pearl gray and moderately viscid, slightly turbid if with gastric secretions - Slight blood streaking = from the intubation procedure - Abnormalities: *large amt. of bld. = suggest CA of Ampulla of Vater *presence of food particles = indicates either pyloric obstruction or pyloric stenosis *sediment or flocculent debris = inflamm. of duodenal mucosa, pancreas or biliary tract
    37. 37. MICROS. EXAM. OF CELLULAR ELEMENTS -should be collected in containers chilled in an ice bath & examined ASAP -examined unstained following centrifugation -Normal: few leukocytes or epithelial cells -Abnormal: *increased # of PMN & exfoliated epith. cells with or without masses of bacteria, enmeshed in mucus = inflam. of the duodenum, bile ducts or pancreas *parasites = rarely seen are larvae of S. stercoralis, cyst or troph of G. lamblia or E. hist., ova of hookworm or ascaris
    38. 38. SUBST. THAT ENHANCE BILE FLOW  1. CHOLERETICS =subs. which increase bile secretion by the hepatic cells ex. Bile salts and secretin 2. CHOLAGOGUES =increase bile flow by causing the contraction of the gall bladder and relaxation of the sphincter of the common bile duct. ex. Magnesium sulfate
    39. 39. CHEMICAL EXAMINATION OF DUODENAL CONTENTS I. EXAMINATION OF STIMULATED BILE Duodenal intubation is performed. Following aspiration of the residual content, 50 to 100 ml. of sterile 25% saturated MgSO4 is introduced through the duodenal tube. After a minute or so, the MgSO4 & duodenal contents are aspirated, the collections are pooled and discarded until a yellow bile first appears, requiring about 2-10 ml. Three fractions of the bile are subsequently collected in separate containers. “A” Bile – the first to appear which is light yellow & watey
    40. 40. After 1 to 3 minutes, it will normally give way abruptly to a viscid deep yellow brown bile – the “B” bile. Eventually, the bile again becomes pale yellow and watery which is the “C” bile. CLINICAL EVALUATION: “A” Bile usually amounts to 5 to 20 ml. “B” Bile is about 30-75 ml. Absence of “B” Bile may be seen in: Advanced Cholecyctitis, Cholelithiasis with Obstruction of the Cystic Duct or Cholecyctctomy
    41. 41.  The finding of Bile Sand (deep red-brown bile microscopically seen as cholesterol crystals or calcium bilirubinate) is highly suggestive of cholelithiasis or calculus in the biliary tract.  Culture of stimulated Bile: Coliform organisms, staphylococci, B-hemolytic streptococci, enterococci and various species of salmonella are often found in an acute or chronic cholecystitis and cholangitis.
    42. 42. TESTS FOR PANCREATIC FUNCTION 1. Determination of Amylase & Body Fluids - for the diagnosis of acute & chronic pancreatitis = increased levels of pancreatic enzymes in the blood & urine 2. Immunoreactive Trypsin Det. In plasma by RIA 3. Secretin Test – the exocrine secretory function of the pancreas can be assessed by duodenal intubation & subjecting the pancreas to stimulation with secretin & pancreozymin. Includes measurement of the volume & quantitative analysis of pancreatic juice for HCO3 & enzyme content specifically Amylase activity.
    43. 43. 4. Augmented Secretin Test - of particular value since augmented stimulation enhance secretory deficiencies as in inflammation & CA. 5. Miscellaneous Tests: A. Leukocytosis & wbc count sometimes reaching 30,000/ cu mm. in acute pancreatitis B. decreasing serum calcium – points to a more serious from of pancreatitis C. hyperbilirubinemia & other liver function tests – with abnormal results
    44. 44. D. Test for malabsorption syndrome (caused by inadequacy of pancreatic secretion resulting from chronic pancreatitis or pancreatic CA) 1. serum carotenoid level 2. glucose tolerance test 3. c-labeled triglyceride breath test 4. starch tolerance test 5. 3-day fecal fat determination 6. d-xylose test (useful to distinguish malabsorption syndrome caused by pancreatic disorders from that of intestinal disorders.) E. Tests for Cystic Fibrosis (mucoviscidosis) of the pancreas
    45. 45. CYSTIC FIBROSIS  Characterized by abnormal secretion of by the various exocrine glands of the body including the pancreas, salivary glands, peritracheal & peribronchial glands. The laboratory diagnosis depends largely of the increase of Na and Cl in the sweat. SWEAT TESTS Principle: Pilocarpine is iontophoresed into the skin to stimulate locally – increased sweat gland secretion. The resulting sweat is absorbed by filter paper or gauze pad, weighed, diluted with water and analyzed for Na & Cl content.
    46. 46. F. Recent Tests that provide a better indicator of pancreatic function as well as diagnosis of pancreatic carcinoma /CA 1. Lactoferrin determination in pancreatic juice - lactoferrin is higher in patients with chronic pancreatitis than in patients with pancreatic carcinoma 2. Det. of Galactosyltransferase Isoenzyme II - found to be raised in pancreatic CA, but is nonspecific; may be elevated in other GIT CA. 3. Tubeless techniques with oral administration of Nbenzal-L-tyrosyl-p-aminobenzoic acid.
    47. 47. T. Y. & BYE BYE Love, S.s.