Endoscopic ultrasound is an imaging test which combines an endoscopic examination with an ultrasound examination. A very thin flexible tube is passed through the mouth, into the throat, and then on through either the bronchi into the lungs or through the esophagus into the stomach. Alternatively, the tube can be passed through the anus and into the lower gastrointestinal tract. A tiny ultrasound transducer is built into this tube, allowing close examination of areas of either the upper or lower gastrointestinal tract, or the respiratory tract. Endoscopic ultrasound can be used to diagnose conditions, to stage cancer, and to access biopsy samples.
Endoscopic ultrasound can be used to evaluate a number of conditions, including:
- Cancer of the esophagus, stomach, pancreas or rectum
- Lung cancer
- Gallstones in the bile duct
- Pancreatic cysts
- Dysfunctional anal sphincter
- Barrett’s esophagus
- Rectal fistulas
Patients who are taking blood thinners, aspirin, or nonsteroidal anti-inflammatory medications may need to discontinue their use in advance of the test, to avoid increasing the risk of bleeding.
After the patient is adequately sedated, he or she will be placed in the appropriate position, depending on what type of examination is being performed. For upper gastrointestinal or respiratory exams, the throat will be sprayed with a local anesthetic which will prevent the gag reflex from interfering with introduction of the endoscope. Air may be introduced into the gastrointestinal tract, in order to expand the area for more easy visualization of the structures.
The endoscope will be passed either through the mouth into the trachea and then through the bronchial tree into the lungs, or through the mouth into the esophagus and on into the stomach. From the stomach, the endoscope can be passed further into the small intestine, where it can be used to access the pancreas as well. Alternatively, the endoscope can be introduced through the rectum into the large intestine for examination of the bowel.
The progression of the endoscope past the various structures will be visible to the examiner on a television monitor. A separate ultrasound monitor allows the examiner to view ultrasound images during the course of the examination. Fine needle biopsy can be performed through the endocscope in order to obtain biopsy samples.
Patients will need to stop eating and drinking for at least six hours prior to the exam. For examinations involving the gastrointestinal tract, enemas and/or laxatives may be used to empty the GI tract of feces. An intravenous line will be placed in order to provide the patient with fluids and sedation during the exam. Sedation will make the passage of the endoscopy tube less traumatic and uncomfortable. The patient will be attached to a variety of monitors to keep track of
Barrett’s esophagus— A condition in which the esophageal tissue closest to the stomach contains highly abnormal cells that have a great likelihood of converting to frank cancer.
Endoscope— A narrow, flexible tube with a fiber optic light on it, used to pass into the body for a variety of medical examinations.
Fine needle biopsy— Use of a very thin type of needle to withdraw cells from an organ, a tumor, or other body tissue, in order to examine those cells for abnormalities (such as malignancy)in a pathology laboratory.
Fistula— An abnormal opening occurring between two organs or an abnormal opening leading to the outside of the body.
Pancreatitis— Inflammation of the pancreas.
Transducer— The instrument that sends sound waves into organs of the body, in order to produce ultrasound images.
blood pressure, heart rate, and blood oxygen level throughout the procedure.
After the test, patients will rest until the sedative wears off. Once their gag reflex has returned, they can begin drinking fluids. After some hours, they can progress to a light diet. Most people can resume their normal diet and activity level within 24 hours of this type of test.
In general, endoscopic ultrasound examinations that are performed without final needle aspiration are relatively low risk. Only about one in 2,000 patients undergoing this procedure develop any kind of complication from it. Possible problems include reaction to the sedatives (such as nausea, vomiting, hives, or skin rash), or swelling or infection of the area where the intravenous line was placed. The most serious complication involves inadvertent perforation (puncture) of the intestinal wall, requiring surgical repair. This is an extremely rare complication.
There is a slightly higher rate of complication when endoscopic ultrasound is performed in conjunction with a fine needle aspiration. Complication rates for this procedure are about 0.5-1.0%. In this case, there is some chance of bleeding if the needle accidentally passes through the intestinal wall. This may require that the patient be hospitalized for observation, or, even more rarely, for a blood transfusion. Infection can also occur following fine needle aspiration. When the procedure involves the pancreas, there is a risk of pancreatic inflammation or pancreatitis, requiring some days of hospitalization and treatment.
Normal results mean that there are no structural abnormalities visualized during the course of the examination. If biopsies are performed, a normal examination would mean that only normal tissue was identified upon pathological examination.
Abnormal results range from the discovery and identification of tumors, cysts, or gallstones, to the demonstration of cancerous tissue upon examination of biopsy material in the pathology laboratory.
Feldman, M, et al. Sleisenger & Fordtran’s Gastrointestinal and Liver Disease, 8th ed. St. Louis: Mosby, 2005.
Goldman, L., D. Ausiello, eds. Cecil Textbook of Internal Medicine, 23rd ed. Philadelphia: Saunders, 2008.
Grainger, R. G., et al. Grainger & Allison’s Diagnostic Radiology: A Textbook of Medical Imaging, 4th ed. Philadelphia: Saunders, 2001.
Mettler, F. A. Essentials of Radiology, 2nd ed. Philadelphia: Saunders, 2005.
Townsend, C. M., et al. Sabiston Textbook of Surgery, 17th ed. Philadelphia: Saunders, 2004.
Rosalyn Carson-DeWitt, MD