For Diagnostic and Therapeutic Intervention
Endoscopic Ultrasound (EUS) is state-of-the art diagnostic imaging, utilizing ultrasound in a unique way to evaluate and diagnose many disorders of the gastrointestinal (GI) tract.
Trans abdominal ultrasound has always been recognized as an excellent imaging modality for evaluating the liver and biliary tract, but has limited pancreatic imaging ability, largely due to obstructing bowel gas. EUS can eliminate problems with "poor imaging windows", since the ultrasound transducer is situated on the top of a standard endoscope and can be introduced into the upper or lower GI tract as easily as other endoscopic devices to allow for enhanced imaging of intra and extramural GI lesions.
Endoscopic Ultrasound (EUS) can visualize the entire thickness of the G I tract wall as a series of discrete layers that correlate to anatomic histology. The ability provides the basis for most of the indications for EUS. Since the EUS transducer can be placed immediately adjacent to specific areas of interest, fine detailed high resolution imaging of the gut wall, as well as extramural structures such as the liver, spleen, pancreas, lymph nodes, and bile ducts, can be obtained.
INDICATIONS FOR EUS
1. GI TUMOR STAGING
- Bile Duct
2. SUBMUCOSAL MASSES OR ABNORMALITIES NOTED ON ENDOSCOPY OR OTHER IMAGING MODALITIES
3. PANCREATICO-BILIARY DISEASE
- Detection of choledocholithiasis, gallstones and microlithiasis
- Idiopathic pancreatitis
- Pancreatic and biliary tumors - diagnosis and staging
- Detection of chronic pancreatitis
- Evaluation of chronic abdominal pain
4. EUS-GUIDED FINE NEEDLE ASPIRATION (FNA) FOR OBTAINING TISSUE DIAGNOSIS
- Pancreatic masses
- Pancreatic pseudocyst
- Submucosal masses
- Staging of non-small cell lung cancer by detecting the presence of posterior mediastinal lymph node metastasis
- Perirectal masses
- Assessing intra-abdominal lymph nodes for metastasis as part of preoperative evaluation
5. EUS-GUIDED CELIAC PLEXUS BLOCK FOR CONTROL OF CHRONIC ABDOMINAL PAIN
- Several studies have shown the efficacy of this approach to relieving the pain associated with intra-abdominal malignancies and chronic pancreatitis.
GASTROINTESTINAL TUMOR STAGING
EUS has been shown to be the most accurate modality for staging esophageal, gastric, rectal, pancreatic, ampullary and biliary cancer. EUS staging is based on the T (tumor), N (nodal) and M (metastasis) classification. EUS staging accuracy, as correlated with surgical findings in many studies, is in the range of 80-90% and exceeds that of Computed Tomography (CT) for these GI tract malignancies.
EUS staging information is valuable in the preoperative evaluation of GI tract tumors since it can help decide operative versus non-operative management and avoid unnecessary surgery and its inherent risks and complications in those patients where curative resection is not possible.
EUS is very accurate for imaging focal lesions of the pancreas, including neuroendocrine tumors, and can detect tumors less than 1 cm. EUS can be used to detect such masses when CT or ERCP are equivocal or suggest a possible mass and EUS-guided fine needle aspiration can be used to obtain tissue sampling and confirm the presence of malignancy. For pancreatic cancer staging and determination of respectability, EUS appears to be one of the most accurate methods of detecting vascular invasion (of the portal vein, SMA or SMV), which is usually the primary reason for unresectability.
SUBMUCOSAL MASSES OR ABNORMALITIES
EUS evaluation of submucosal masses can differentiate intramural from extrinsic etiologies and for intrinsic masses, determine the extent of penetration into the GI tract wall. Intramural lesions can be further differentiated by depth of penetration and ultrasound characteristics. For example, lipomas arise from the fourth layer or muscularis propria and are less echogenic or hypoechoic. EUS guided FNA can also be performed to confirm the diagnosis in difficult cases.
Clinical decisions can then be made based on the EUS findings and benefit those patients with clearly benign lesions by avoiding unnecessary exploratory surgery.
INFORMATION ABOUT THE PROCEDURE
EUS is a safe procedure with low complication rate. Conscious sedation is used to minimize patient discomfort. The procedure takes somewhat longer than a standard endoscopy and the length of time depends on whether FNA is performed. Patients having upper GI EUS are asked to remain NPO past midnight before the exam. Patients with rectal EUS are asked to prep with Fleets enemas on the day of the exam prior to arrival. For patients potentially having EUS guided FNA, we ask that they not take any aspirin, non-steroidal medications, or anticoagulants for at least five to seven days prior to the procedure.