Pancreatic duct diameter

Last revised by Arlene Campos ◉ on 26 Feb 2024

The diameter of the (main) pancreatic duct is a commonly assessed parameter in imaging.

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The duct diameter is greatest at the head and neck region and is slightly narrower towards the body and tail. Its normal reported value ranges between 1-3.5 mm in <50 year old and 2-5 mm in 70-79 year old individuals with mean reported values (rounded to the nearest 0.5 mm) being 5,8,11:

  • head

    • 3.5 mm (<50 years)

    • 5 mm (70-79 years)

  • body

    • 2.5 mm (<50 years)

    • 3 mm (70-79 years)

  • tail

    • 1.5 mm (<50 years)

    • 2 mm (70-79 years)

Pancreatic duct diameter may also increase by 1.0-2.2 mm with deep inspiration, compared to complete exhalation, in a small proportion of adults 3.

Abnormal dilatation of the pancreatic duct indicates obstruction of the normal flow of pancreatic secretions due to a distal (i.e. downstream) tumor or stricture. This can occur with acute pancreatitis, chronic pancreatitis or pancreatic neoplasms. Rarely, pancreatic duct dilatation can occur with tumoral hypersecretion of mucin (e.g. from intraductal papillary mucinous neoplasms).

Some authors suggest a main pancreatic duct dilatation (≥2.5 mm) without an obvious cause as an independent predictor of developing pancreatic cancer 6.

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Some publications recommend double duct dilatation needing extensive work-up while single duct dilatation >5 mm, especially in those without any evidence of chronic pancreatitis, also needing careful follow-up (time-frame not specified) 9,10.

Imaging findings favoring malignant over benign duct dilatation include 11:

  • distal duct dilatation

  • long (≥6.1 mm) segment dilatation

  • abrupt transition

  • absence of a duct penetrating sign

  • presence of attenuation

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