Endoscopic ultrasound (EUS) is a medical exam using an instrument that combines a tiny ultrasound unit with an endoscope. Ultrasound uses sound waves that are passed into the body tissues and which then “echo” back to a sensor.
The sensor creates a visual image on a screen that can be evaluated by the physician.
EUS is an ultrasound test of the digestive tract. The ultrasound probe is placed on the end of the endoscope. An endoscope is a lighted, flexible tube that the physician can pass through the esophagus (the tube through which food passes to the stomach). Endoscopes may also be passed through the rectum. With a standard endoscopy, the physician can directly view the inside surface of the digestive tract. With EUS, the ultrasound creates an image of the underlying area. Thus, the physician can get a view of the tissues and organs beneath the intestinal surface.
Purpose of the EUS
The digestive tract, also called the gastrointestinal or GI tract, includes the mouth, throat, esophagus, stomach, intestines, and rectum. Other organs like the gallbladder and pancreas which contribute to the digestion of foods, are part of the digestive or GI system. When a patient is having discomfort and symptoms that suggest a problem in the GI system, the physician will order tests to help with the diagnosis. Stomach ulcers and intestinal polyps are examples of conditions that clearly show on the inside lining of the intestine. In these cases a standard is all that is needed. However, to see deeper into the underlying tissues or the surrounding area. EUS may be used to evaluate the following:
- Blood vessels
- Gallstones within the gallbladder and bile duct
- Abnormalities of the rectum
- Tumors and lymph nodes that lie beneath the intestinal wall
- Growth of known tumors
- Tumor removal or recurrence
- Follow-up of benign appearing tumors
Biopsy of tumors can also be done through the EUS scope.
Preparing for the EUS
The physician should be informed of all medications the patient is taking. The patient should also check with the physical before stopping any medications. When the test is done on the upper GI tract, the patient does not eat or drink anything for a period of about eight hours before the exam. When EUS is done through the rectum, the colon (lower intestine) must be cleansed. Normally, the patient uses a liquid diet along with laxatives or enemas to cleanse the lower bowel. If biopsies are anticipated, the phisician advises the patient about any blood thinning medications. These include aspirin and Coumadin (warfarin), which are usually stopped for up to five days before the exam. These medications may increase the risk of excessive bleeding from a biopsy.
Performing the EUS
EUS is usually performed as an outpatient exam in an area of the hospital set aside for GI procedures. An anesthetic spray may be used to numb the back of the throat. The patient lies on the left side and is given a sedative to produce a drowsy, sleepy state. The EUS scope is then inserted through the mouth or rectum, and eased through to the area to be examined. An EUS scope is flexible and can be easily moved around the various bends in the digestive tract. When the scope is in position, the ultrasound mechanism produces the images needed for the examination. These images are carried electronically into a computer system that displays them on a video screen for the physician to view.
Permanent photographs of the video images are made to verify what has been found, and to use for later study and comparison. In general, it takes 20 to 40 minutes to complete the exam. The patient is then taken to a recovery area for observation until sedation wears off. While most of the needed information is available to the physician immediately, a biopsy report will require several days. A follow-up appointment is then necessary to review the results.
Side Effects and Risks
During the procedure, patients are routinely monitored to be sure that there are no complications from medications. Following the procedure, the patient may have a mild sore throat for a few hours. Because of the sedation, patients should not drive, operate heavy machinedy, or make important decisions for up to six hours followingg the procedure. Therefore, someone should be available to drive the patient home.
The ability of EUS to get so close to an area to be examined makes this test reliable and preferable to more invasive techniques. In general, EUS is a very safe procedure. There is a very slight risk of the endoscope tearing the intestinal tract, which would require surgery. Rarely, excessive bleeding may occur with a biopsy.
EUS is an effective way of examining the digestive tract, and the tissues and organs that lie outside it. This exam may be used with other studies to give a life-like picture of conditions in the GI tract. Serious complications are very uncommon. EUS allows the physician a high degree of accuracy in making a diagnosis, so that an effective form of therapy can usually be provided.