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Rectosacral fascia (Waldeyer's fascia)

The rectosacral fascia, also known as Waldeyer’s fascia, is a dense fibrous fascial layer in the pelvis that anchors the rectum to the sacrum. It plays an important role in rectal support and is a critical surgical landmark during rectal dissection, especially in total mesorectal excision for rectal cancer. This fascia separates the presacral space from the posterior rectal space and provides a connective tissue plane for safe dissection.

Synonyms

  • Waldeyer’s fascia

  • Fascia of Waldeyer

  • Rectosacral connective fascia

Location and Attachments

  • Superior attachment: Arises from the presacral fascia overlying the sacrum, typically at the level of the S2 vertebra

  • Course: Runs anteriorly and inferiorly from the sacrum, forming a dense fibrous sheet between the rectum and sacrum

  • Inferior attachment: Inserts onto the posterior wall of the rectum, blending with the rectal fascia propria

  • Extent: Forms a fascial partition that separates the presacral venous plexus and hypogastric nerves posteriorly from the rectum anteriorly

Relations

  • Anteriorly: Posterior rectal wall and mesorectum

  • Posteriorly: Presacral space, presacral venous plexus, and hypogastric nerves

  • Superiorly: Presacral fascia along sacrum

  • Inferiorly: Blends with fascia propria of the rectum

Function

  • Anchors the rectum to the sacrum, maintaining its anatomical position

  • Provides a surgical dissection plane between rectum and sacrum

  • Protects presacral venous plexus and hypogastric nerves during surgery

  • Contributes to pelvic organ stability and rectal support

Clinical Significance

  • Critical landmark in rectal cancer surgery: division of rectosacral fascia allows safe mobilization of rectum during total mesorectal excision (TME)

  • Protects presacral veins: inadvertent injury during dissection can cause life-threatening hemorrhage

  • Important in pelvic trauma or infection as a barrier between presacral and perirectal spaces

  • May be thickened or distorted in pelvic fibrosis, prior surgery, or infiltrative rectal tumors

MRI Appearance

T1-weighted images:

  • Appears as a thin, dark linear structure between rectum and sacrum

  • Fat around it appears bright, enhancing fascial delineation

T2-weighted images:

  • Low signal intensity linear band separating rectum and presacral space

  • Thickening or irregularity may be seen with tumor invasion or fibrosis

STIR (Short Tau Inversion Recovery):

  • Normal fascia remains dark

  • Inflammatory or edematous changes adjacent to fascia appear bright against the dark fascial band

T1 Fat-Sat Post-Contrast:

  • Fascia itself shows minimal to no enhancement

  • Pathology (fibrosis, tumor infiltration) may cause focal or diffuse enhancement around the fascia

CT Appearance

Non-Contrast CT:

  • Fascia usually not directly visible; identified as a potential thin soft tissue density plane between rectum and sacrum

  • Presacral fat provides contrast to localize it

Post-Contrast CT:

  • Normal fascia does not enhance significantly

  • May appear as a thin linear structure separating rectum and sacrum when fat planes are preserved

  • Tumor infiltration or inflammatory thickening appears as enhancing soft tissue obliterating this fascial plane

MRI image

rectosacral fascia (Waldeyer’s fascia MRI axial anatomy image-img-00000-00000

MRI image

rectosacral fascia (Waldeyer’s fascia MRI sagittal anatomy image-img-00000-00000