Endoscopic Ultrasound (EUS)/Fine Needle Aspiration (FNA)
Endoscopic ultrasound (EUS) is a technique using sound waves known as ultrasound during an endoscopic procedure to look at or through the wall of the gastrointestinal tract. This technique allows physicians to see organs and structures not typically visible during gastrointestinal endoscopy, such as the layers of the gastrointestinal tract wall, the liver, pancreas, lymph nodes, and bile ducts. The scope used for EUS is similar to a regular endoscope with the added component of an ultrasound transducer. Under continuous real-time ultrasound guidance, a thin needle can be advanced into these structures to obtain an aspirate of the tissue. This technique is known as a fine needle aspirate (FNA). The cells obtained from the FNA can be smeared on a slide and analyzed for abnormalities such as cancer. The cell analysis is called cytology.
EUS with FNA has revolutionized the ability to diagnose and stage cancers of the gastrointestinal tract and assess the pancreas. Gastrointestinal cancers can be looked at with EUS and their depth of penetration into the intestinal wall can be determined. Any suspicious appearing lymph nodes can be biopsied using EUS/FNA. The pancreas is another organ that is well visualized with EUS. Abnormalities such as tumors and cysts of the pancreas can be carefully evaluated using EUS and then biopsied with FNA.
Lung cancer is also routinely staged by performing an EUS/FNA of the lymph nodes in the chest that can be seen by looking through the esophagus, as these nodes are often the first location to which lung cancer spreads. If a malignant (cancerous) node is confirmed on EUS/FNA, the patient will often require medical therapy first before considering lung surgery. In this way, EUS/FNA can help direct the appropriate first line of therapy.
There are many new applications of EUS using FNA. Researchers are looking to deliver chemotherapeutics into small pancreatic cancers and cysts. Nerve blocks using EUS/FNA to inject numbing medicines into the celiac ganglia, a major nerve cluster, are now routinely performed in patients with pain due to pancreatic cancer.
Reviewed November 2010