EUS
Meaning of EUS: An ultrasound probe carried down the gullet on a scope, close enough to image organs the skin hides.
Definition of EUS
EUS stands for endoscopic ultrasound, an examination that combines a flexible viewing tube with an ultrasound probe at its tip. Passed through the mouth or the rectum, it rests the probe against the gut wall, so the sound waves travel only a short distance. That closeness produces far sharper images of the pancreas and other nearby organs than scanning through the skin can achieve.
How does it differ from an ultrasound scan on the skin?
The physics is identical. What changes is the distance and what lies in between.
| Scan through the skin | EUS | |
|---|---|---|
| Probe position | On the body surface | Inside the gut, against the wall |
| Obstacles | Fat, bowel gas, bone | Almost none |
| Detail | Lower | Millimeter scale |
| Preparation | None or minimal | Fasting and sedation |
What can it show?
The pancreas is the classic target, because it sits deep in the abdomen behind the stomach and is poorly seen from outside. EUS also assesses how deeply a tumor of the esophagus, stomach or rectum has grown into the wall, which is central to staging. It detects small gallstones in the bile duct, examines lymph nodes beside the airways, and characterizes cysts. The moving picture it produces is a sonogram, the same kind of image as any other ultrasound.
Can samples be taken during it?
Yes, and this is much of its value. A fine needle can be advanced from the endoscope through the gut wall into a mass or lymph node while the operator watches the needle on screen. Tissue obtained this way often settles a diagnosis without open surgery. Fluid can be drained from a collection by the same route, and a stent can be placed to keep a blocked duct open.
What does the examination involve?
It is normally a day case. The stomach has to be empty, so food is withheld beforehand, and sedation is given because the scope is larger than a standard gastroscope and the examination takes longer. The tube passes through the mouth for the upper abdomen and chest, or through the rectum for the lower bowel. Most people are aware of little of it. A sore throat afterward is common and settles quickly. The recognized risks are those of any endoscopy, bleeding and a small chance of a tear in the wall, with inflammation of the pancreas added when a needle sample is taken from that gland.
Also known as
Used in a sentence
Staging was completed with EUS, which showed tumor extension through the muscular layer.
Good to know
Because the probe sits against the gut wall, EUS resolves detail that surface ultrasound and computed tomography can miss, and it allows a needle sample to be taken during the same procedure.