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Nasolacrimal duct (Tear duct)

The nasolacrimal duct is a crucial anatomical structure responsible for draining tears from the lacrimal sac into the nasal cavity. Part of the lacrimal drainage system, it plays a significant role in tear film maintenance and eye health. Its dysfunction can result in watery eyes (epiphora) or recurrent infections. Radiological imaging, particularly MRI and CT, is essential for evaluating duct patency and identifying pathologies such as obstruction or inflammation.

Synonyms

  • Tear duct

  • Nasolacrimal canal

  • Ductus nasolacrimalis

  • Dacryocystic duct (less common, but sometimes used)

Function

  • Facilitates drainage of tears from the eye into the inferior nasal meatus of the nasal cavity

  • Maintains moisture of the ocular surface by removing excess tears

  • Prevents stagnation of tears, thereby reducing risk of infections (e.g., dacryocystitis)

  • Plays a minor role in immune defense by flushing away debris and microorganisms

MRI Appearance

  • T2-weighted images:

    • The nasolacrimal duct appears as a tubular, hypointense (dark) structure compared to the surrounding soft tissue

    • The lumen, if fluid-filled (e.g., in obstruction), may show high signal intensity (bright)

  • T1-weighted images:

    • The duct itself is typically hypointense (dark)

    • The lumen may be slightly hyperintense if containing proteinaceous or mucoid material

  • STIR (Short Tau Inversion Recovery):

    • The bony canal remains hypointense

    • Edema, inflammation, or retained fluid within or around the duct appears hyperintense (bright), highlighting pathology such as dacryocystitis

CT Appearance

  • The nasolacrimal duct is best visualized on thin-section axial and coronal images

  • Appears as a bony canal within the maxilla, extending from the lacrimal sac to the inferior nasal meatus

  • The duct itself is a small, air or fluid-filled soft tissue density within the canal

  • CT is superior for assessing bony detail and identifying causes of obstruction (e.g., fractures, stones, neoplasms)

MRI images

Nasolacrimal duct (Tear duct) mri image

MRI images

Nasolacrimal duct (Tear duct) mri

CT image

Nasolacrimal canal