EUS- An endoscopic ultrasound scan uses an endoscope with an ultrasound probe attached to create detailed pictures of internal organs and structures.
This scan combines two types of test – endoscopy and ultrasound. The operator uses a thin flexible telescope (endoscope) with an ultrasound probe attached to look inside your gut (gastrointestinal tract). By putting the endoscope into the upper part of the gut, the scan can create pictures of the surrounding structures, not just inside the gut. The ultrasound probe is used to create detailed pictures of the body, including the lungs, pancreas, liver, gallbladder and stomach.
The scan can also look at other structures lower down in the body by inserting the endoscope through the back passage (rectum) into the lower part of the gut.
Endoscopic ultrasonography (EUS) allows your doctor to examine your esophageal and stomach linings as well as the walls of your upper and lower gastrointestinal tract. The upper tract consists of the esophagus, stomach and duodenum; the lower tract includes your colon and rectum.
During the EUS procedure, the doctor will spray the back of the throat with a numbing spray and the patient lie in a left lateral position, following that patient receives the sedation and the doctor will examine your gullet, stomach, bile duct, liver and pancreas in a systematic approach to get to the conclusion.
he video camera at the tip of the endoscope sends pictures to a screen. The operator watches the screen for abnormalities of the oesophagus, stomach and duodenum. Air is passed down a channel in the endoscope into the stomach to make the stomach lining easier to see. This may cause you to feel ‘full’ and want to belch.
The ultrasound probe will send back signals which make a picture of the parts of the body surrounding the probe. You will not feel the ultrasound working but may be able to see the pictures on a TV screen near the bed if you wish.
The operator may take one or more small samples, depending on why the test is done and what they see. This is painless. The biopsy samples are sent to the laboratory for testing and to look at under the microscope. The endoscope is then gently pulled out.
The scan usually takes about 10-20 minutes. However, you should allow at least two hours for the whole test, to prepare, give time for the sedative to work (if you have one), for the endoscopy itself and to recover. An EUS does not usually hurt but it can be a little uncomfortable, particularly when you first swallow the endoscope.
Endoscopy is an excellent way to look at the lining of the gut and take samples from parts of the gut. By attaching an ultrasound probe, the endoscope can also help to create detailed pictures of parts of the body that are difficult to show in other scans like CT or MRI, as the sound waves are passed very close the part of the examination in the GI tract. Ultrasound is a high-frequency sound waves that you cannot hear but which can be emitted and detected by special machines.
Ultrasound travels freely through fluid and soft tissues. However, ultrasound is reflected back (it bounces back as ‘echoes’) when it hits a more solid (dense) surface. For example, the ultrasound will travel freely through blood in a heart chamber. However, when it hits a solid valve, a lot of the ultrasound echoes back. Another example is that when ultrasound travels though bile in a gallbladder it will echo back strongly if it hits a solid gallstone.
So, as ultrasound ‘hits’ different structures of different density in the body, it sends back echoes of varying strength. This helps to build a picture of the structures surrounding the probe. Hence the EUS is used in even finding small stones in bile duct while the other scans like CT or MRI fail to detect the minute details.