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Rectococcygeal muscle

The rectococcygeal muscle is a slender fibromuscular structure of the pelvic floor that connects the posterior rectal wall to the coccyx. It is sometimes referred to as part of the rectal suspensory apparatus. Though smaller and less recognized than the levator ani group, it plays an important role in maintaining the anorectal angle and providing posterior support to the rectum. It is clinically relevant in imaging and surgery for pelvic floor disorders, rectal prolapse, and anorectal function studies.

Synonyms

  • Rectococcygeal ligament (when fibrous component dominates)

  • Posterior rectal suspensory muscle

  • Musculus rectococcygeus

Location and Attachments

  • Origin: Posterior surface of the rectum, near the anorectal junction

  • Course: Extends posteriorly and slightly inferiorly from the rectal wall toward the coccyx

  • Insertion: Anterior surface of the coccyx and occasionally the sacrococcygeal ligament

Relations

  • Anteriorly: Rectum and mesorectal fascia

  • Posteriorly: Coccyx and presacral fascia

  • Laterally: Levator ani muscles (especially iliococcygeus fibers)

  • Superiorly: Rectal ampulla

  • Inferiorly: Anal canal and external anal sphincter

Function

  • Provides posterior anchoring and stabilization of the rectum

  • Helps maintain the anorectal angle in coordination with the puborectalis

  • Contributes to continence by supporting the posterior rectal wall

  • Prevents excessive anterior displacement of the rectum during defecation

Clinical Significance

  • Weakness or disruption may contribute to rectal prolapse or pelvic floor dysfunction

  • May be visualized or evaluated in dynamic pelvic floor MRI studies

  • Serves as a landmark in colorectal surgery and pelvic dissection

  • Involved in surgical reconstructions of anorectal support structures

MRI Appearance

T1-weighted images:

  • Appears as a thin band of low-to-intermediate signal intensity posterior to the rectum

  • Fat in presacral space appears bright, providing contrast

T2-weighted images:

  • Muscle demonstrates low-to-intermediate signal intensity

  • Surrounding fat appears bright, helping define the muscle

  • Edema or fibrosis may appear as altered signal within the band

STIR (Short Tau Inversion Recovery):

  • Muscle remains dark in normal state

  • Pathological changes (inflammation, fibrosis) may appear bright

  • Presacral fat is suppressed, allowing better delineation of the muscle

T1 Fat-Sat Post-Contrast:

  • Normal muscle enhances mildly and uniformly

  • Inflammation or neoplastic involvement shows heterogeneous or irregular enhancement

CT Appearance

Non-Contrast CT:

  • Muscle appears as a thin soft tissue density band between the rectum and coccyx

  • Surrounded by lower-density presacral fat

  • Calcification or fibrosis may appear as focal high-density areas

Post-Contrast CT:

  • Normal muscle shows mild uniform enhancement

  • Pathological involvement (tumor, infection, fibrosis) may show irregular or nodular enhancement

  • Presacral abscess may displace or obscure the muscle with rim-enhancing fluid collections

MRI image

Rectococcygeal muscle MRI AXIAL anatomy image-img-00000-00000

MRI image

Rectococcygeal muscle MRI Coronal anatomy image-img-00000-00000

CT image

Rectococcygeal muscle CT AXIAL IMAGE

CT image

Rectococcygeal muscle CT sagittal anatomy image-img-00000-00000