Have you ever wondered why we’re asked to fast before medical imaging procedures? Though all the tests may not require fasting, some procedures demand it. In this blog we delve into the significance of fasting in obtaining clear and precise results in medical imaging procedures. Understanding the rationale behind it helps you be better equipped for the procedure.
Here are some reasons why fasting is necessary for medical imaging procedures
Better Image Quality
Fasting helps reduce the presence of gas and undigested food in the digestive system. When there’s less interference from these substances, the imaging results are clearer and more accurate. This is particularly important for tests like abdominal ultrasounds, CT scans, and MRIs.
Contrast Studies
Some imaging tests involve the use of contrast dyes, which are substances that enhance the visibility of certain tissues or organs. Fasting before the test helps ensure that the contrast agent is not diluted or affected because of the food in the digestive system, allowing it to work more effectively.
Avoiding Aspiration
For certain tests like endoscopy or certain X-rays, fasting is necessary to reduce the risk of aspiration. Aspiration occurs when food or liquid enters the lungs, which can be dangerous and may cause complications.
Reducing Bowel Movement
Fasting helps to minimize bowel movement during the test, especially for imaging tests that involve the lower gastrointestinal tract, such as colonoscopy or barium enema. In some cases, it is necessary to avoid potential complications, such as the risk of vomiting and aspiration during anesthesia or sedation.
Imaging procedures and fasting requirements
Ultrasound
Ultrasound utilizes soundwaves to generate detailed images of the body’s internal organs and structures. During an abdominal ultrasound, undigested food in the stomach and urine in the bladder can obstruct the sound waves, making it challenging for the technician to obtain a clear image of the abdomen.
Eating or drinking before the procedure can cause the gallbladder to contract, making it more difficult to identify any abnormal growths or polyps inside the gallbladder. Therefore, fasting before an ultrasound is often recommended to ensure clearer and more accurate images. For adults, a fasting period of 6-8 hours prior to the ultrasound is typically advised. This helps to improve the effectiveness and precision of the ultrasound examination.
Computed Tomography (CT) Scan
Fasting may be necessary for certain CT scans, especially those involving the abdomen or pelvis. Contrast agents is a special dye which helps ensure proper absorption of the contrast by the target organs, providing clearer images. Radiologists suggest fasting prior to CT scan since the side effects of contrast agents, includes nausea and vomiting,
Magnetic Resonance Imaging (MRI)
Positron Emission Tomography (PET) Scan
PET scans typically require fasting, especially for whole-body scans, aiming to enhance accuracy by having patients avoid high-carbohydrate foods for several hours. This practice ensures optimal scan results by reducing glucose absorption in certain tissues, minimizing interference with image interpretation.
Endoscopy
For procedures like gastrointestinal endoscopy or colonoscopy, fasting is essential to ensure that the stomach and intestines are empty. This reduces the risk of complications like aspirations and provides a clear view of the organ.
Fasting complications
If you have any concerns or questions before a medical imaging test, be sure to discuss them with your doctor.
Continue taking your regular medications before the test, unless specifically instructed by the doctor. Some medications are temporarily stopped as they interfere with the test results. Be sure to tell your doctor about all the medications you’re currently taking.
For individuals with diabetes, fasting can lead to complications. If you have diabetes and need to fast for a test, it’s crucial to have a conversation with your doctor beforehand. Request written instructions on how to handle a hypoglycemia episode if it occurs during fasting. Your doctor can provide guidance on managing your blood sugar levels during the period to ensure your safety and well-being.
Conclusion