Home  | About Us  | News & Events  | Contact Us  | Directions

Health Information Services Physicians Referring Physicians Hospitals and Clinics Academic Affiliates Patients & Visitors Faculty & Staff

Ellis Fischel Cancer Center 115 Business Loop 70 W. Columbia, MO 65203 (573) 882-2100 About Clinical Trials Directions Disease Sites Ellis Fischel Gala Ellis Magazine E-mail a Patient E-mail Us Employment Gift Shop Guest House Index A to Z Make a Gift Margaret Proctor Mulligan     Breast Health Center Phone Numbers Physician Information Support Groups Treatment Programs Submit Comments

Endoscopic Ultrasound

Endoscopic ultrasound (EUS) is a novel procedure that has revolutionized gastrointestinal tract imaging. Although other standard indications exist and new uses are reported in the medical literature regularly, the most common indication for performing endoscopic ultrasound is the staging of gastrointestinal tumors.

Instruments used
Instruments used for endoscopic ultrasound are called echoendoscopes. These tools combine endoscopic and ultrasound imaging in one instrument. Echoendoscopes look highly similar to standard endoscopes, with an ultrasound probe mounted on the tip of the instrument.

Advantages
The advantage of EUS over traditional transabdominal ultrasonography is that the area of interest is imaged from within the gastrointestinal lumen. By eliminating the need to image through skin, muscle and fat, higher-frequency ultrasound waves can be used, thus resulting in greater resolution.

The higher frequencies also allow imaging of the layers of the gastrointestinal wall (mucosa, submucosa, muscularis propria and serosa). By determining the depth of invasion of gastro-intestinal malignancies, a tumor (T) stage can be determined.

Additionally, lymph nodes as small as a few millimeters can be visualized with EUS. Lymph nodes associated with a known malignancy that are greater than 1 cm and have certain ultrasound features are almost certainly involved with malignancy. Tumor and nodal staging subsequently is used to develop treatment strategies for cancer patients.

Comparisons
EUS has been compared to CT for T-staging and nodal staging, or N-staging, of GI tumors. When surgical staging is used as the gold standard, the accuracy of EUS T-staging of esophageal cancer is 65 percent to 90 percent compared to a CT accuracy of 30 percent to 70 percent. N-staging accuracy is 65 percent to 90 percent with EUS compared to 50 percent to 80 percent with CT. EUS similarly is superior for staging gastric, pancreatic and rectal cancer. However, EUS is not the test of choice for assessing distant metastases.

Further capabilities
Echoendoscopes with fine needle aspiration (FNA) capabilities now are available, allowing for the sampling of lymph nodes and masses adjacent to the gastrointestinal wall. For example, mediastinal lymph nodes can be sampled to assist in staging thoracic malignancies, including esophageal and lung cancer, or when the cause of lymphadenopathy is uncertain.

In esophageal cancer patients, the celiac axis routinely is imaged during EUS. Lymph nodes identified in this area can be aspirated through the gastric wall. Positive celiac axis nodes indicate an unresectable tumor, saving a patient from an unnecessary esophagectomy. Furthermore, EUS-guided FNA can be used to sample pancreatic masses to verify a suspected malignancy.

Therapeutic EUS
Therapeutic EUS is being used increasingly. For example, EUS is useful in guiding transgastric or transduodenal drainage of pancreatic pseudocysts. By imaging the gastric/duodenal wall adjacent to a pseudocyst, one can determine the depth of the wall in a particular region and if vascular structures lie between the pseudocyst and gastric/duodenal wall. EUS can be used to identify the celiac axis. Using echoendoscopes with FNA capabilities, anesthetics can be injected to provide a celiac plexus block for patients with unresectable pancreatic cancer.

Evaluating subepithelial lesions
EUS also is useful in evaluating subepithelial lesions, especially in the stomach. By identifying the layer from which the lesion arises, one can determine the likely etiology. For example, solid lesions arising from the gastric submucosa are likely lipomas, while lesions arising from the muscularis propria usually are leiomyomas or leiomyosarcomas. EUS also can differentiate solid from fluid-filled lesions and aid in identifying, for example, gastroesophageal varices and pancreatic pseudocysts. Centers with expertise in pancreatic imaging use EUS criteria to assist in diagnosing chronic pancreatitis.

The patient's perspective
From the patient's perspective, an EUS examination is similar to a standard upper endoscopy or, in the case of rectal ultrasonongraphy, a flexible sigmoidoscopy. EUS-guided FNA carries additional, although small, risks. EUS costs slightly more than standard endoscopy.

Summary
In summary, endoscopic ultrasound is the most accurate imaging technique for assessing the tumor stage of gastro-intestinal malignancies. The procedure is extremely valuable in assessing any structure that lies in proximity to the gastrointestinal lumen. Several diagnostic and therapeutic indications for EUS exist, and many more likely will develop in the future.

References

1. Cahn M, Chang K, Nguyen P, et al. Impact of endoscopic ultrasound with fine-needle aspiration on the surgical management of pancreatic cancer. Am J of Surg. 1996;172: 470-472.

2. Reed CE, Mishra G, Sahai AV. Esophageal cancer staging: improved accuracy by endoscopic ultrasound of celiac lymph nodes. Ann Thorac Surg. 1999; 67:319-321.

3. Rosch T. Endoscopic staging of esoph-ageal cancer: a review of literature results. Gastrointest Endosc Clin N Am. 1995;5:537-547.

4. Silvestri GA, Hoffman BJ, Bhutani MS, et al. Endoscopic ultrasound with fine-needle aspiration in the diag-nosis and staging of lung cancer. Ann Thorac Surg. 1996;61:1441-1445.

5. Van Dam J, Sivak MV, eds. Gas-trointestinal endosonography. Philadelphia, Pa.: W.B. Saunders Company; 1998.

6. Williams DB, Sahai AV, Aabakken L, et al. Endoscopic ultrasound guided fine needle aspiration biopsy: a large single center experience. Gut. 1999;44:720-726.