Tell your doctor in advance of the procedure about all medications that you’re taking and about any allergies (especially Latex) you have to medication. He / she will tell you whether or not you can continue to take your medication as usual before the EUS examination. 
 

For EUS of the upper gastrointestinal tract, you should have nothing to eat or drink, not even water, usually six hours before the examination. Your doctor will tell you when to start this fasting.
 

For EUS of the rectum or colon, your doctor will instruct you to either consume a large volume of a special cleansing solution or to follow a clear liquid diet combined with laxatives or enemas prior to the examination. The procedure might have to rescheduled if you don’t follow your doctor’s instructions carefully. 
 

Your endoscopist will use a thin, flexible tube called an endoscope. Your doctor will pass the endoscope through your mouth or anus to the area to be examined. Your doctor then will turn on the ultrasound component to produce sound waves that create visual images of the digestive tract.

EUS provides you doctor more detailed pictures of your digestive tract anatomy. Your doctor can use EUS to diagnose the cause of conditions such as abdominal pain or abnormal weight loss. Or, if your doctor has ruled out certain conditions, EUS can confirm your diagnosis and give you a clean bill of health.
 

EUS is also used to evaluate an abnormality, such as a growth, that was detected at a prior endoscopy or by x-ray. EUS provides a detailed picture of the growth, moreover tissue or cells can be studied by needle aspiration aswell which can help your doctor determine its nature and decide upon the best treatment. 
 

In addition, EUS can be used to diagnose diseases of the pancreas, bile duct and gallbladder when other tests are inconclusive.

Like other endoscopy procedures, EUS is safe and well tolerated. But no procedure is without risk, which with EUS are quite rare. Complication rate for EUS without the fine needle aspiration is about one in two 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. 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 gut 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.

As mentioned, EUS provides good image of internal organ, however the other investigation such as CT scan, MRI, PET/CT, can provide additional information as well, especially the organ that located outside the field of EUS. (Normally EUS gives picture within 7-8 cms. from the tip of endoscope.)

• Tumor staging ( Lung cancer, cancer of gastrointestinal tract, Pancreatic tumor )
• Large or thickening fold or growth at the wall of gastrointestinal tract
• Various disease of gall bladder, bile duct and pancreas