ROLE OF EUS IN PATIENTS WITH ESOPHAGEAL AND GASTRIC DISEASES

ROLE OF EUS IN PATIENTS WITH ESOPHAGEAL AND GASTRIC DISEASES.

Sergey V. Kantsevoy, MD, PhD, Director of Therapeutic Endoscopy
Institute for Digestive Health and Liver Disease At Mercy Medical Center
Baltimore, Maryland, USA

Endoscopic Ultrasound (EUS):

Relatively new diagnostic modality, introduced in 1980
Original indication for EUS was early diagnosis and staging of the GI malignancies
The indications for EUS continue to grow and include now a wide range of benign and neoplastic diseases of the GI tract

EUS Basics:

Acoustic penetration is inversely proportional to the frequency of the ultrasound beam
Spatial resolution is directly proportional to the frequency of the ultrasound beam
Traditional transabdominal ultrasound requires deep tissue penetration (15-20cm) – needs 3.5 MHz
Endoscopy allows delivery of the source of ultrasound beam into direct proximity to evaluated intraabdominal or mediastinal structure
Necessary depth of penetration is limited to 0.5 - 3 cm
EUS utilizes sources of the ultrasonic beam with the frequency of 7.5 – 30 MHz, which tremendously improves spatial resolution

Available Equipment for EUS:

A. Dedicated echoendoscopes

1.Radial array

Frequency 7.5-12 MHz
Penetration 8-10 cm
Complete visualization
No biopsy capabilities

2.Linear array

Frequency 7.5 MHz,
Penetration 8-10 cm
Allows FNA under the EUS guidance

B. Ultrasound miniprobes
Very high frequency 20-30 MHz
Depth of penetration limited to 0.5 – 2.0 cm
Very high resolution 0.07-0.18 mm
Outer diameter of the probe - 2 mm
The probe is passed via the biopsy channel of the endoscope into esophagus, stomach, biliary or pancreatic duct
The position of the probe is localized fluoroscopically

Clinical Applications of EUS:

EUS in patients with biliary diseases
EUS in patients with pancreatic diseases
EUS for mediastinal diseases and lung cancer staging
EUS for rectal cancer
EUS for advanced esophageal cancer
EUS for early esophageal and gastric cancer
EUS for submucosal lesions of upper GI truct

EUS for early esophageal and gastric cancer

To evaluate depth of penetration (T-stage)
EUS accuracy for T1 lesions – 80% (Rosch T, 1995)
Overall EUS accuracy for T-stage 71-92% (Rosch T, 1995)

EUS for advanced esophageal cancer

EUS allows preoperative T- and N-stage determination
Overall accuracy rates are 85% for T-stage and 75% for N-stage (Mallery S, 2000)
Accuracy for M-stage is only 60-70% (Rosch T, 1995)
EUS performed only after CT documented absence of metastases

EUS for submucosal lesions of upper GI tract:

To distinguish lesions inside GI tract wall from compression from outside (adjacent organs)
To assess size of composition of the lesion
To evaluate blood supply
To guide the decision about endoscopic removal of the lesion