Gastric Fluid Analysis

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What is Gastric fluid analysis? Gastric fluid analysis is a medical method used to measure the stomach’s secretions and other liquid substances. 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 diagnosing ulcer disease, evidence of gesture analyses is now… Read More

Gastric Fluid Analysis

What is Gastric fluid analysis?

Gastric fluid analysis is a medical method used to measure the stomach’s secretions and other liquid substances. Gastric fluid analysis requires a sample of secretions present in the stomach.

Gastric Fluid Analysis
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Why are gastric secretions analyzed?

With the emergence of more sophisticated techniques for diagnosing ulcer disease, evidence of gesture analyses is now much more specific. The gastric analysis is chiefly done for estimation of acid excretion, as well as to:

  • Confirm suspected Z-E (Zollinger Ellison) syndrome.
  • Demonstrate achlorhydria (absence of hydrochloric acid in the gastric juice produced in the stomach).
  • Estimate or show parietal cell mass.

Several factors can affect the estimation of gastric acidity. The total acid output is calculated as a volume over time to provide a better picture of acid secretory ability rather than determining the acid concentration. Gastric fluid can be extracted from the stomach by passing a tube through the nose. This test is most commonly done to check for blood in the upper gastrointestinal system.

How is a gastric fluid analysis prepared?

These are some tips to keep in mind when preparing for gastric analysis. 

  • Patients should not eat for at least 10 to 12 hours prior to the analysis (usually the night preceding the analysis).
  • Patients shouldn’t take any medication, especially anticholinergic agents, H2 blockers, or antacids, a few hours before the procedure, as consumption of these medications 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 them to prepare their mind for the analysis as well.

Routine Requirements 

Routine Requirements for gastric fluid analysis
Picture Courtesy: bioscience

When carrying out gastric fluid analysis, the following equipment is used:

  • 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.

Gastric Fluid Analysis Procedure 

Before the Procedure,

Picture Courtesy: slideshare
  • 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 the 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 a few inches before continuing with the intubation.
  • During the insertion, reassure the patient, instruct them 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 tube’s position. 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. The patient may discard the 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 at 6mg per kg body weight. It has very few side effects. Another is Betazole (Histology), whose minimum dose is 1.5mg/kg body weight, given subcutaneously.

  • After the intramuscular stimulants resume gastric acid collection again 15 minutes apart, a total of 4 to 8 sample collections are done (with pentagastrin peak response is 30 to 90 minutes). In separate containers, the samples are collected and marked 1, 2, 3, 4, 5, 6, 7, and 8.
  • After the basal and stimulated gastric juice collection, the specimen is 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).

What are the risk factors of gastric fluid analysis?

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. In addition, the stress of intubation for hours coupled with the ejection of saliva to avoid diluting the stomach contents is likely to initiate or increase emotional and psychological stress on the patient.

What are the most common complications of gastric fluid analysis? 

Following gastric tube removal, complications can be possible: vomiting, nausea, abdominal distention, and/or pain. Sore throat also is likely to occur. The risk is 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 spells. 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).


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 with the gastric acid stimulation test results. 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 a duodenal ulcer; the highest level of secretion points to Zollinger – Ellison (Z-E) syndrome. 


What is the gastric function test?

Test of gastric function is of value for many aspects in developing drugs and their delivery systems.
Intragastric and esophageal pH meter and gastric juice analysis 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?

Gastric juices in their natural state are often clear in color.
HCL is an essential component of 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?

Normal stomach fluid volume is between 20 and 100 ml. The pH is acidic (1.5-1.5 to 3.5).

What is the function of gastric juice?

Gastric juice is a mixture of hydrochloric Acid (HCL), pepsin, and lipase. Its primary function is to kill microorganisms that have been swallowed and prevent infectious agents from reaching your intestine.

What happens if the stomach pH is too high?

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