Endoscopic Ultrasound (EUS)combines endoscopy and ultrasound in order to examine the digestive tract and the surrounding tissue and organs. Endoscopy refers to the procedure of inserting a long flexible tube via the mouth or the rectum to visualize the digestive tract. Ultrasound uses high-frequency sound waves to produce images of the organs and structures inside the body. By placing an ultrasound machine at the tip of an endoscope tube, the doctor can obtain high quality ultrasound images of the organs inside the body.
- 01. Reasons for the Exam
- 02. Equipment
- 03. Benefits and Alternative Testing
- 04. Side Effects and Risks
- 05. Preparation
- 06. Before the Procedure
- 07. The Procedure
- 08. After the Procedure
01. Reasons for the Exam
EUS is used to provide information about the layers of the intestinal wall, nearby organs, or lymph nodes and blood vessels. EUS can also include obtaining tissue samples or biopsies to help in diagnosing enlarged lymph nodes or masses seen on other imaging studies. EUS is useful in several situations including but not limited to
- Evaluating chronic pancreatitis, masses or cysts of the pancreas.
- Studying bile duct abnormalities including stones in the bile duct or gallbladder, or cancer of the bile ducts.
- Studying certain sub mucosal lesions such as nodules or “bumps” that may be hiding in the intestinal wall covered by normal appearing lining of the intestinal tract
- Staging (or determining the extent of) certain cancers.
The endoscope is a flexible instrument that can be steered around the bends in the digestive tract. The endoscope has an optically sensitive chip in its tip that transmits an image on a large video screen. The endoscopic ultrasound instrument an endoscope with an ultrasound transducer on the tip. The transducer transmits images produced by sound waves to a separate video screen. Using EUS, your doctor can place the ultrasound probe in the gastrointestinal tract very close to the area of interest. In this way the best possible picture can be obtained. During the procedure the doctor may obtain tissue samples by passing a special needle, under ultrasound guidance, through the endoscope. The tissue or cells obtained by the needle can be examined by a pathologist under a microscope. The process of obtaining tissue with a thin needle is called fine needle aspiration (FNA).
03. Benefits and Alternative Testing
The benefit of endoscopic ultrasound is that it allows the doctor to obtain high quality images of the intestinal tract and surrounding organs. It can provide more exact pictures than routine x-rays, CAT scans or even MRI scans when evaluating areas of the GI tract, pancreas or bile ducts. In addition tissue samples may be obtained during this procedure.
An alternative to a endoscopic ultrasound may be x-rays, CAT scans or MRI scans. Of these tests only CAT scans can sample tissue, but many times the area of interest is not reachable on CT and is only accessible by EUS. In most cases the alternative tests will not provide the detailed information that can be obtained by EUS.
04. Side Effects and Risks
Like other endoscopy procedures, EUS is safe and well tolerated and complications are rare. No procedure is without risk, however. The complication rate for EUS without the fine needle aspiration is about one in ten thousand. This is similar to the complication rate of other endoscopy procedures. Sometimes, patients can develop reactions such as hives, skin rash or nausea to the medications used during EUS. A lump may appear in the area of the vein where the IV was placed. This usually resolves over time. Should it persist, you should contact your physician. The main complication of serious note is perforation (making a hole in the intestinal wall) that may require surgical repair. This is quite rare and all precautions are taken to avoid it.
When FNA is performed complications occur more often but are still uncommon (0.5-1.0%). Passing a needle through the intestinal wall may cause minor bleeding. If unusual bleeding occurs, the patient may be hospitalized briefly for observation, but blood transfusions are rarely needed. Infection is another rare complication of FNA. Infection can occur during aspiration of fluid from cysts and antibiotics may be given before the procedure. If the FNA is performed on the pancreas, pancreatitis (inflammation of the pancreas) can rarely occur. Pancreatitis requires hospitalization, observation, rest, IV fluid, and medication for abdominal pain. It usually resolves spontaneously in a few days.
Your doctor will want to know about your health status especially if you have any allergies, other significant health problems such as heart disease, lung disease, diabetes mellitus, etc. If there is a possibility of fine needle aspiration (FNA), the doctor may want to check your blood for proper clotting. It is important to inform your doctor of any family history of bleeding problems or if you are taking medications that interfere with blood clotting (such as Coumadin) or platelet function (such as aspirin, Motrin, ibuprofen, Aleve, and other NSAIDs). The wisest is to inform your doctor of any prescription or non-prescription medication you might be taking.
EUS is performed with sedation so you will not be able to return to work or to drive for the rest of the day. It also means that you will need someone to take you home as this is usually an out-patient procedure.
You will need to have an empty stomach that means no food or drink for 6 or more hours. In case of a rectal EUS you will need to take some enemas or laxatives. In either case, full instructions will be given to you.
06. Before the Procedure
When you arrive for your procedure, a brief medical history will be reviewed with you by a nurse. Please bring a list of your current medications and any allergies to medications. You will be asked to remove your clothing and change into a patient gown.
07. The Procedure
An intravenous (IV) catheter will be placed in your hand or forearm so that medication can be given for sedation. Most of the effects of the sedation last for 15-60 minutes, and you probably will not be able to recall the procedure afterwards.
Once you are sedated, the special endoscope will be inserted and the procedure started. You will only feel minimal discomfort, if any, during the entire procedure. The physician will observe the inside of your intestinal tract on a TV monitor and the ultrasound image on another monitor. The entire procedure generally takes 30 to 90 minutes depending on the complexity and whether fine needle aspiration (FNA) is performed.
08. After the Procedure
After the procedure you will be sleepy for up to one hour and be unable to drink or walk. When you are fully awake, your companion will be able to take you home where you should rest for the remainder of the day. Light meals and fluids are allowed. The bloating which you may feel from the air used to expand the GI tract will only be temporary. Should your throat be mildly sore, for a day or two, salt-water gargles will provide relief.