D- GASTRIC FUNCTION TESTS. In some diseases of Stomach & Duodenum alterations in gastric secretion occurs, thereby chemical examination of gastric contents has limited but specific value in diagnosis & assessment of disorders of upper GIT. N.
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In some diseases of Stomach & Duodenum alterations in gastric secretion occurs, thereby • chemical examination of gastric contents has limited but specific value in diagnosis & assessment of disorders of upper GIT.
N • Hence to get complete data of gastric fn, the contents of stomach should be examined • During resting period • During digestion after meals • After stimulation Gastric juice secreted in 24 hrs is about 1500 ml to 2000ml.
Chief constituents of Gastric juice • HCl………Parietal cells / oxyntic cells - it activates the zymogen pepsinogen to pepsin by partial proteolysis, also helps in absorption of iron and calcium. • Pepsinogen..........Chief cells - Pepsins act on proteins and polypeptides & cleave peptide bonds adjacent to aromatic amino acids
Gastrin: hormone secreted by G cells, stimulates secretion of HCl. • Intrinsic Factor: Parietal cells, is a glycoprotein required for absorption of Vit B 12
Gastric lipase: Chief cells. Act on Triglycerides, convert to Fatty acids and glycerol • Rennin : is seen in infants but not in adults. • Alkaline Mucus
Indications of Gastric Function Tests • To diagnose Gastric Ulcers • To exclude the diagnosis of Pernicious Anaemia & Peptic ulcer in Pt with GU. • For presumptive diagnosis of Zollinger Ellison Syndrome • To determine the completeness of Surgical Vagotomy.
CLASSIFICATION OF GFTs • Analysis of Resting contents(Gastric Residuum) • Fractional Test Meal Analysis • Analysis after Stimulation # Alcohol stimulation # Caffeine stimulation # Histamine stimulation
CONTD…… # Augmented Histamine test # Insulin stimulation # Pentagastrin test • Tubeless Gastric Analysis • Other relevant tests are estimation of Sr.Gastrin, Sr.Pepsinogen levels, Tests for Occult blood and Tests for H.Pylori
N • Analysis of resting contents: • Volume : 20-50ml after a night fast > 100-120 ml….is abnormal Volume.. - Hypersecretion of Gastric juice - Retention due to delayed emptying - Regurgitation of duodenal contents.
N N 2) Consistency : Fluid, should not contain food residues. 3) Colour: Clear/ Colourless/ slight yellow/green.. Bright red / dark red / brown…abnormal dark brown seen in bleeding gastric ulcer, coffee ground appearance seen in Ca stomach.
N 4) Bile:Small amounts are insignificant, but increased in Intestinal Obstruction / Ileal Stasis. 5) Mucus: in small amounts, increased in gastritis , Ca Stomach. 6) Free & Total Acidity: determined by titrating a portion of the sample with a standard solution of NaOH.
Free acidity measures only HCl, Topfer’s reagent is used as indicator. • Total acidity includes HCl and other organic acids , Phenolphthalein is used as indicator
Normal values - Free Acid : 0-30 mEq / L > 50 mEq / L indicates Hyperacidity - Total Acid : 10-40 mEq / L 7) Organic Acids: like lactic acid & butyric acid in large amounts indicate achlorhydria/hypochlorhydria.
Fractional Test Meal Analysis Diff. meals used are -Ewald test meal (2 pieces toast+250 ml tea) -Oatmeal porridge -Riegel meal..not used normally
Procedure: After removing residual contents, meal is given. With intervals of 15 minutes contents of stomach are removed ,strained & analysed. • Normally free acid rises steadily from 15 min – ½ hr/45 min, and decreases.
Abnormal responses are: 1) Hyperchlorhydria / Hyperacidity: when free acid is > 50mEq / L Seen in - Duodenal ulcer, Gastric ulcer, Gastric cell hyperplasia, After Gastroenterostomy,
Contd….. Gastric Neurosis, Hyperirritability, Pylorospasm , Pyloric Stenosis , Chr. Cholecystitis, Zollinger Ellison Syndrome.
2) Hypochlorhydria / Hypoacidity: Seen in Ca Stomach , Atonic Dyspepsia 3) Achlorhydria: No HCl is seen but pepsin is present. Seen in Ca Stomach, Chr.Gastritis, Partial Gastrectomy, Pernicious Anaemia, Hyper thyroidism, Myxoedema.
ACHYLIA GASTRICA : is a condition where both enzymes and acids are absent Seen in – Advanced Ca Stomach -- Advanced cases of Gastritis -- Pernicious Anaemia -- Subacute combined degeneration of spinal cord.
Analysis after Stimulation : • Alcohol Stimulation : -stimulant used is 7% ethyl alcohol. - the residual contents removed after overnight fasting, 100ml alcohol is given, samples are taken every 15 min & analysed for free, total acidity,peptic activity,blood, bile,mucus.
Advantages : - more easy to administer - consumed better than porridge - gastric response is rapid - emptying of stomach is more rapid than porridge.
Disadvantages: - stimulus with alcohol is not so strictly physiological as with oatmeal. - stimulus is more vigorous compared to oatmeal - rather high levels of free acidity seen.
2) Caffeine Stimulation : - Caffeine Sodium Benzoate,500mg dissolved in 200ml of water is given. - Advantages are similar to that of alcohol stimulation. • 3) Histamine Stimulation Test: - it is a powerful stimulant for secretion of HCl, acts on oxyntic cells(specific H2receptors)
Indications : To differentiate “ True “ Achlorhydria from “ False “ Achlorhydria • Types of Histamine test - Standard Histamine test - Augmented histamine test (Kays test).
Standard Histamine test: SC injection of Histamine 0.01mg/kg bwt , is given. # Results - Absence of HCl…true achlorhydria, seen in pernicious anemia. - Increase in HCl…Duodenal Ulcer • Augmented Histamine test (Kays) : larger dose, 0.04mg/kg b wt of histamine acid phosphate, SC.
Indications: -to show inability to secrete acid as in pernicious anemia & subacute combined degeneration of cord. - to assess max possible acid secretion in diagnosis & Surg.Rx of Duodenal ulcer. • Disadv : larger dose causes severe allergic reactions,hence another antihistaminic given to prevent.
Procedure: After overnight fast, residual contents are analysed and contents are collected every 20 min for an hr. • Halfway through this period 4ml of mepyramine maleate (anthisan), given IM, to block H1 receptors. • At the end of hr histamine acid phosphate,0.04mg / kg bwt, SC given.and contents removed every 15 min for 1 hr.
Recently, histamine analogue,called “Histalog”(3 beta-amino ethyl pyrazole) is used instead of histamine • recommended dose –10-50mg • No side effects seen hence no need to use an antihistamine to block H1 receptors.
4) Insulin Stimulation test (Hollander’s test): Hypoglycemia produced by insulin is a potent stimulus of gastric acid secretion. • Indications: to see the effectiveness of vagotomy in pts with duodenal ulcer. • 15units of soluble insulin given IV • Disadv: Hypoglycemia
Results: in pts with DU , before operation there is marked & prolonged output of acid in response to insulin. After successful vagotomy, there is no response and acid level is very low.
5) Pentagastrin test: Pentagastrin, synthetic peptide, having biologically active sequence of gastrin.It is “Butyl oxy carbonyl- beta alanine Trp-Met-Asp-Phe CONH2” • Dose— 6 microgram/kg bwt. SC
It is a potent stimulator, causing max stimulation after assessing basal secretion rate, hence it is a measure of Total Parietal Mass. • Procedure: after removing the residual contents , the gastric juice secreted for next 1 hr is collected as a single sample, which is called BASAL SECRETION.
Then pentagastrin is given & 4 samples are collected with 15 min intervals. • Basal Acid Output (BAO) is output in mmol / hr, in basal secretion. • Maximal Acid Output(MAO) is output in mmol/hr, given by sum of the 15 min acid output after stimulation. • Peak Acid output (PAO) is output of 2
N Consecutive 15 min samples having highest acid content and the value is multiplied by 2. • Result: basal secretion rate is 1-2.5mEq/hr, after pentagastrin stimulus..it is 20-40mEq/hr. - in DU…. 15-83mEq/hr - in ZE syndrome..basal secretion is > 10 mEq / hr
Tube Less Gastric Analysis : • it avoids discomfort of naso gastric tube • Used only as a screening test. • Fasting secretion is stimulated by histalogue , after 1 hr dye bound resin “Diagnex Blue” with “ Azure A” is given orally.
In the presence of HCl resin releases dye,which is absorbed & later excreted in urine • The quantity of dye in urine provides indication of presence /absence of HCl. • It is not reliable in pts with renal diseases, urinary retention,malabsorption,pyloric obstruction etc.
N N OTHER TESTS: • Serum Gastrin : is estimated by Radio Immuno Assay. level is < 10 pico moles/L, in Zollinger Ellison Syndrome it is > 100 pmol/L. • Serum Pepsinogen : level is 30-160units/ml - in pernicious anaemia…very low/absent - in DU…> 200 units/ml
CONCLUSION • Gastric Function tests are of limited but specific value in diagnosing and assessing some disorders of Upper GIT.