Definition & Overview
Gastric aspiration is a diagnostic procedure used to diagnose cases of pulmonary tuberculosis in children and adults. The procedure involves obtaining gastric juices from the stomach and testing them for an active tuberculosis infection. Gastric aspiration is mostly used in children under six years old who are unable to produce sputum. However, it is also used in adults who have negative results for tuberculosis (TB) on sputum smear examinations.
Despite of the availability and effectiveness of treatment for TB, the disease is still considered one of the world’s biggest threats according to the World Health Organisation (WHO). Over a million people succumb to the condition every year.
The key to surviving the disease is to detect it before it can cause severe damage to the respiratory system. Standard tests for the detection of a TB infection include skin and blood tests. However, such tests can only indicate the presence of a TB infection and not the disease itself. To determine if the patient has the disease, a sputum and chest x-ray test are performed.
Unfortunately, sputum smear tests are not always accurate and can sometimes provide a false negative result. If a doctor suspects the presence of tuberculosis disease despite three negative sputum smear tests, a gastric aspiration procedure is performed.
The process of obtaining gastric aspirates should not be confused with the gastric aspiration condition. Gastric aspiration also refers to a condition wherein a patient loses control of his or her airway functions. If this happens and the patient vomits, gastric juices and other stomach contents may enter the lungs resulting in a life-threatening condition.
In a gastric aspiration procedure to test for tuberculosis, the process is controlled to minimise the chances of stomach contents entering the lungs.
Who Should Undergo & Expected Results
As mentioned earlier, gastric aspiration is performed on children under 6 years old who usually have trouble producing sputum. It is also performed on adults who have undergone sputum smear tests but believed to have false negative results.
Additionally, gastric aspiration has also become a preferred diagnostic method to test for the presence of tuberculosis in patients who have undergone a renal allograft procedure. Renal allograft procedures are notoriously known for being associated with a variety of infections, one of which is tuberculosis. As such, patients who have undergone the procedure may also need to undergo gastric aspiration if tuberculosis is suspected.
The results of a gastric aspiration procedure are highly accurate. Should the results be negative and substantiated by other examinations, such as a chest x-ray, any suspicion of the disease can be dismissed. Gastric aspiration is safe and has minimal risks and possibility of complications. However, patients can expect a bit of discomfort before, during, and after the procedure due to the preparations required and method of obtaining the needed gastric juices.
How is the Procedure Performed?
Before a gastric aspiration procedure is performed, an attempt will be made to get the patient to expectorate sputum. If gastric aspiration is to be performed in an adult, it would mean that standard tests for tuberculosis have failed to provide an accurate result and the doctor still suspects the presence of the disease.
A gastric aspiration is usually performed early in the morning. The patient should have undergone a fasting period overnight for not less than 4 hours.
The procedure should be performed in a sterile environment. In most cases, it will be performed in an examination room, but may also be performed on the patient’s bed as long as all working surfaces have been disinfected.
The patient is asked to lie flat on the bed and turn towards the left or right side. Parents, guardians, and anybody else assisting with the procedure will need to wear a mask to minimise the risk of contracting the disease, if present.
The doctor will then insert a tube into the nostril and guide it down towards the stomach. An empty syringe is attached to the other end of the tube to aspirate the stomach contents. Aspiration is performed three times with the patient being placed in different positions.
At least 5ml of aspirate stomach contents needs to be retrieved. If the amount is insufficient, the doctor may need to perform a gastric lavage procedure. This involves passing at least 10 ml of sterile water down the tube and leaving it inside the stomach for around 3 minutes. The contents of the stomach will then be aspirated until sufficient amount of gastric juices is obtained.
Once enough contents have been obtained, the doctor will remove the tube and this completes the procedure.
Possible Risks & Complications
Gastric aspiration is safe and there is minimal risk of transmitting the disease if present. However, the patient may experience the following during the procedure:
- Pain and discomfort while the tube is being inserted
- Bleeding from the nose due to trauma (epistaxis)
- A gagging feeling
- Trauma to the vocal cords
- Perforation of the oesophagus
- Anxiety, especially in younger children
The majority, if not all, of the risks and complications can be managed or even prevented. The skills of the doctor or nurse performing the procedure are important as the patient, especially a child, will need to be comforted. In some cases, the child may also need to be strapped down to the bed or examination table to prevent unnecessary movements that can cause damage to organs or tissue.
Carlos M. Perez-Velez;”Standard Operating Procedure – Nasogastric Aspiration for the bacterial confirmation of pulmonary tuberculosis in children”; https://drtbnetwork.org/sites/default/files/SOP-GastricAspirationSentinel_Project.pdf
Francis J. Curry National Tuberculosis Center;”Gastric Aspirates: Patient Preparation and Procedure”; http://www.currytbcenter.ucsf.edu/sites/default/files/gapatientprep.pdf