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Anatomy of the anal canal and perianal structures as defined by phased-array magnetic resonance imaging

G L Morren1, R G Beets-Tan, J M van Engelshoven

  • 1Departments of General Surgery and Radiology, University Hospital of Maastricht, Maastricht, The Netherlands. geert_morren@hotmail.com

The British Journal of Surgery
|October 31, 2001
PubMed
Abstract

Insights

Phased-array MRI accurately images anal canal and perianal anatomy without endoluminal coils. This study details normal anatomy and identifies significant sex-based differences in structures like the external anal sphincter and perineal body.

Area of Science:

  • Anatomical imaging
  • Pelvic floor anatomy
  • Magnetic Resonance Imaging (MRI)

Background:

  • Endoluminal MRI has been used to image the anal canal and perianal structures.
  • Phased-array MRI offers an alternative by avoiding endoluminal coils that can distort anatomy.

Purpose of the Study:

  • To describe the normal anatomy of the anal canal and perianal structures using phased-array MRI.
  • To identify and quantify sex differences in these anatomical structures.

Main Methods:

  • Phased-array MRI was performed on 14 men and 19 nulliparous women.
  • Measurements of the anal canal, puborectalis, external anal sphincter, perineal body, superficial transverse perineal muscle, bulbospongiosus, ischiocavernosus, and anococcygeal body were taken in multiple planes.
  • Statistical analysis was used to determine sex differences.

Main Results:

  • The lateral anal canal was significantly longer than anterior and posterior portions.
  • The anterior external anal sphincter was shorter in women (30% of canal length) than men (38%).
  • The perineal body was thicker and more defined in women, while the bulbospongiosus was thicker in men. Ischiocavernosus and anococcygeal body dimensions were similar between sexes.

Conclusions:

  • Phased-array MRI is a non-invasive and accurate method for visualizing normal anal canal and perianal anatomy.
  • The technique provides detailed anatomical descriptions and highlights significant sex-based variations.

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