Sonographic parallel channel sign: a reappraisal

Area of Science:

• Medical Imaging
• Hepatobiliary System Anatomy
• Diagnostic Ultrasonography

Background:

• Traditionally, ultrasonography interpreted parallel tubular structures near hepatic ducts as abnormal dilation.
• Advancements in electronically focused transducers allow visualization of peripheral tubular structures previously overlooked.

Purpose of the Study:

• To determine the prevalence and diameter of tubular structures near hepatic ducts in healthy individuals.
• To differentiate normal anatomical variants from pathological biliary dilatation using advanced ultrasonography.

Main Methods:

• Measured diameters of all visible tubular structures near right and left hepatic ducts in 50 healthy subjects.
• Compared the diameters of these tubular structures to accompanying portal vein branches.

Main Results:

• Tubular structures were frequently observed (e.g., 100% for right hepatic ducts).
• Ducts proximal to hepatic ducts measured ≤2 mm in diameter and averaged ~20% of portal vein diameters.
• Most ducts (except 4% of left lateral inferior) were ≤40% of their respective portal vein diameters.

Conclusions:

• The presence of parallel channels near hepatic ducts on ultrasonography does not inherently indicate biliary dilatation.
• Accurate measurement and comparison with portal vein diameters are crucial for correct interpretation of these structures.