Gastric Fluid Analysis

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WHAT IS GASTRIC FLUID ANALYSIS? Gastric fluid analysis is a medical method used to measure the secretions and other liquid substances present in the stomach. Gastric fluid analysis requires a sample of secretions present in the stomach. WHY ARE GASTRIC SECRETIONS ANALYZED? With the emergence of more sophisticated techniques for the diagnosis of ulcer disease, […] Read More

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Gastric Fluid Analysis

WHAT IS GASTRIC FLUID ANALYSIS? Gastric fluid analysis is a medical method used to measure the secretions and other liquid substances present in the stomach. Gastric fluid analysis requires a sample of secretions present in the stomach. WHY ARE GASTRIC SECRETIONS ANALYZED? With the emergence of more sophisticated techniques for the diagnosis of ulcer disease, evidence of gesture analyses are now much specific.  The gastric analysis is chiefly done for estimation of acid excretion, as well as to:
  • Confirm suspected Z-E syndrome.
  • Demonstrate achlorhydria (absence of hydrochloric acid in the gastric juice produced in the stomach).
  • Estimate or show parietal cell mass.
The estimation of gastric acidity is affected by certain factors. Total acid output (as a timed volume) is determined to reflect a more vivid picture of acid secretory capacity; instead of determining the concentration of acids produced. With the aid of a tube passed through the nose and into the stomach, gastric fluid can be obtained from the stomach. The most common reason for this test is to look for blood in the upper gastrointestinal tract. GASTRIC FLUID ANALYSIS PREPARATION The following relevant tips should be noted while carrying out preparations before the gastric analysis:
  • Patients should not eat for 10 to 12 hours before the analysis (usually the night before the day of the analysis).
  • Patients shouldn’t take any medication, especially anticholinergic agents, H2 blockers, antacids, since the night before as they can alter the results.
  • Patients should be weighed before the procedure.
  • The health worker should explain the procedure to the patient in simple words, to enable him/her to prepare his/her mind for the analysis as well.
Routine Requirements The following equipment also is used when carrying out gastric fluid analysis:
  • A radio-opaque stomach tube (16 French sizes).
  • 50ml plastic or glass syringe.
  • 1ml tuberculin syringe.
  • Emesis basin.
  • 100ml graduated cylinder.
  • Adhesive tape.
  • Lubricant.
  • Indicator solution, such as phenol red.
Medical Personnel (Team)
  • Physician.
  • Unit nurse.
  • Medical technologist.
  • Patients should remove all dentures.
  • The technologist should lubricate the nasogastric tube.
  • The technologist examines the nostrils of the patient and chooses the one (while the patient is still sitting upright with neck flexed) through which breathing is easier and the nostril is wider.
  • He gently pushes the radio-opaque stomach tube through the patient’s nostril (intubation). Sometimes the tube may get curled up in the pharynx, causing excessive coughing or gagging. This prevents further passage; at this time, the tube is drawn back some few inches before continuing with the intubation.
  • During the insertion, reassure the patient, instruct him/her to swallow, and continue to swallow throughout the intubation period. After the tube has progressed to about 40cm (the first mark on the tube), the patient may be allowed to keep his head comfortably.
  • Continue intubation gently until the fourth mark (65cm) is reached.
  • The technologist tapes the tube to the patient’s nose with adhesive tape.
  • The technologist sends the patient to an x-ray for fluoroscopy to check the position of the tube. The tube should lie along the lesser curvature with its tip in the atrium of the stomach.
During The Procedure,
  • Empty the stomach contents with a 50ml syringe; continue until the gastric juice is finished.
  • Record the pH, volume, and color. You may discard this residual volume. (If the residual volume is more than 100ml or food particles are present, the possibility of outlet obstruction should be considered.)
  • After emptying the stomach of the residual volume, begin a collection of gastric juice under basal conditions. At least four samples should be collected each fifteen minutes apart in separate containers. 
Collect either manually with a syringe, or by using a suction pump. Inject about 50ml of air down the nasogastric tube to keep it wide open during the procedure.
  • Spot-check the gastric fluid specimen to know whether the patient is making acid or is not (achlorhydria).
  • After collecting gastric juice under basal conditions, augmented or stimulated gastric analysis may be carried out as follows: 
Any of the two stimulants can be used (based on age, choice, and availability). Pentagastrin (available as Peptavion) is most commonly used, administered by subcutaneous injection in the dose, 6mg per kg body weight. It has very few side effects.  Another is Betazole (Histology), and its minimum dose is 1.5mg/kg body weight, given sub-cutaneously.
  • After the intramuscular stimulants, resume gastric acid collection again 15 minutes apart, a total of 4 to 8 collections (with pentagastrin peak response is 30 to 90 minutes). The samples are collected and marked 1, 2, 3, 4, 5, 6, 7, 8, in separate containers.
  • After the basal and stimulated gastric juice collection, the specimen are forwarded to the laboratory for evaluation of the following values:
  • Basal acid output (BAO).
  • Maximum acid output (MAO). This is the sum of the four highest consecutive 15 minutes samples after stimulation.
  • Peak acid output (PAO). This is the sum of the two highest consecutive 15-minute samples multiplied by 2.
  • Basal acid output and maximum acid output ratio as a percentage (BAO/MAO × 100).
COMPLICATIONS Following the removal of the gastric tube, such complications as vomiting, nausea, abdominal distention, and/or pain can be possible. Sore throat also is likely to occur.  The risk that the gastric tube may be improperly inserted, entering the trachea instead of the esophagus. If this happens, the patient will have difficulty breathing and/or coughing spell. Also, a patient who finds it difficult to swallow the tube and has an overactive gag reflex may witness a transient rise in blood pressure (due to anxiety).  Other complications may include:
  • Bleeding.
  • Dysrhythmia.
  • Laryngospasm.
  • Esophageal perforation.
  • Decreased mean p0₂ (a measure of blood oxygen levels).
RESULTS Values for the basal acid output test and gastric acid stimulation test vary from one laboratory to another, but are usually within the following ranges:
  • Fasting volume; 20-100ml.
  • Fasting pH; ˂2.0ml.
  • BAO for men; 0-5mmol/hour.
  • BAO for women; 0-4mmol/hour.
  • MAO for men; 5-26mmol/hour.
  • MAO for women; 7-15mmol/hour.
An abnormal basal acid output is considered non-specific and must be evaluated together with the results of the gastric acid stimulation test. However, elevated secretion may be predictive of different types of ulcers and distinctly elevated results may imply Zollinger – Ellison (Z-E  syndrome.)   In situations of a depressed secretion, gastric cancer may be suspected, while a complete absence of secretion may depict pernicious anemia. Elevated gastric secretion levels in the gastric acid stimulation test may suggest duodenal ulcer; the highest level of secretion points to   Zollinger – Ellison (Z-E) syndrome. Your doctor may request the measurement of your plasma gastrin by radioimmunoassay when your gastric acid level is out of no



Both the basic acid output test and the gastric acid stimulation test require gastric intubation through the mouth or nose. None of these tests is recommended for patients suffering from esophageal problems, severe gastric hemorrhage, aortic aneurysm, or congestive heart failure.

Patients sensitive to pentagastrin may not be recommended for gastric acid output tests. Intubation following patient fasting overnight (12 hours) poses a risk of injury to the esophageal wall. The stress of intubation for hours coupled with ejection of saliva to avoid diluting the stomach contents is likely to initiate or increase emotional as well as psychological stress on the patient.


  • What is the gastric function test?

Test of gastric function is of value for many aspects in the development of drugs and their delivery systems. 

Intragastric and oesophageal pH meter and analysis of gastric juice can be used to assess therapy of disorder associated with either increased acid output or gastroesophageal reflux disease.

  • What is the color of gastric juice?

In tier normal state, gastric juices are usually clear in color. HCL is an important component in gastric juice. It is a strong acid produced by the parietal cells in the corpus pepsin and absorption of nutrients  

  • What is the pH value of the stomach?

The normal volume of stomach fluid is 20 to 100 ml and the pH is acidic (1.5 to 1.5 to 3.5).

  • What is the function of gastric juice?

Gastric juice is a combination of hydrochloric acid (HCL), lipase, and pepsin. Its main function is to inactivate swallowed microorganisms, thereby inhibiting infectious agents from reaching the intestine.

  • What happens if the stomach pH is too high?

Having a high level of stomach acid can increase your risk of developing another stomach-related health condition. This includes a Peptic ulcer. Peptic ulcers are sore that can develop when gastric acid begins to eat away the lining of your stomach.