Endoscopic Ultrasound (EUS) Overview

Types of EUS Scopes

1. Radial EUS Scope

   • Imaging Plane: Perpendicular to the scope axis, providing a 360° view.
   • Setup: Ensure no air bubbles when filling the balloon with saline.

2. Linear EUS Scope

   • Imaging Plane: Parallel to the scope axis, allowing visualization along the wall but not 360°.
   • Special Feature: Can perform biopsies with a needle through the scope.
   • Setup: Similar balloon requirements as radial scopes.

Role in Imaging

• Purpose: Examine the wall of the GI tract and structures outside it (lymph nodes, blood vessels, adjacent organs like pancreas, liver, spleen).

Esophagus Imaging Example

• Cancer Progression:
  • Starts from mucosa, extends through submucosa, muscularis propria, and adventitia.
  • Affects lymphatics and nodes, changing lymph node shape from oval (benign) to round (cancerous).
• Staging:
  • T-Stage: Tumor involvement in the esophagus wall.
  • N-Stage: Lymph node involvement.
  • Distant Metastasis: Evaluated with CT or MRI.

Differences Between Regular EGD and EUS

• EGD:

  • Assesses cancer from the lumen side and allows for biopsy.
  • Cannot determine depth of spread or nodal involvement.

• Radial EUS:

  • Scans to determine tumor staging and nodal staging.

• Linear EUS:

  • Same as radial with added ability for fine needle aspiration (FNA) of suspect lymph nodes.

Pancreatic Evaluation

• Radial EUS Scope: Views pancreas and ductal structures.

• Linear EUS Scope:

  • Used for pancreatic cancer diagnosis via FNA.
  • Determines nodal staging and vessel involvement (e.g., superior mesenteric artery/vein, celiac artery).

• Cystic Lesions Evaluation:

  • Differentiates between pseudocysts, mucinous cystic neoplasms, etc.
  • Allows fluid aspiration from cysts and biopsies from cyst walls.

Therapeutic Uses and Innovations

• EUS-Guided Anastomosis: Techniques like gastrojejunostomy, hepaticogastrostomy.
• Ablative Procedures: Radiofrequency ablation for tumors.

Complications of EUS

1. Perforation: Particularly in obstructed esophageal cancer cases.
2. Bleeding: Associated with FNA.
3. Infection: Possible from cyst aspiration, requiring antibiotics.
4. Pancreatitis: Rare but can occur post-FNA or biopsy.
5. Sedation Reactions: Possible as procedures are done under sedation.

These notes encompass key points about EUS, its applications, differences in scope types, imaging roles, and associated complications.