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Sacral lymph nodes

The sacral lymph nodes are a small but clinically important group of lymph nodes located in the presacral space, along the course of the lateral and median sacral vessels. They play a role in draining pelvic organs and form part of the pelvic lymphatic chain that is critical in gynecologic, urologic, and colorectal oncology. Enlargement of sacral lymph nodes can be a sign of local infection, inflammation, or metastatic disease, especially from cervical, rectal, or prostate cancers.

Synonyms

  • Presacral lymph nodes

  • Retrorectal lymph nodes

  • Sacral chain lymph nodes

Location and Groups

  • Found in the presacral space, anterior to the sacrum and posterior to the rectum

  • Closely associated with the median sacral vessels and lateral sacral arteries

  • Often grouped as medial sacral nodes (along midline near sacral promontory) and lateral sacral nodes (along lateral sacral vessels)

Relations

  • Anteriorly: Rectum and mesorectum

  • Posteriorly: Sacrum and presacral fascia

  • Laterally: Ureters, iliac lymph nodes, sacral vessels

  • Superiorly: Continuous with common iliac lymph nodes

  • Inferiorly: Connect with coccygeal and lower presacral lymphatic chains

Function

  • Drain lymph from:

    • Posterior pelvic organs (rectum, prostate, cervix, vagina)

    • Pelvic peritoneum and sacral region

  • Act as a filtering station for tumor cells and pathogens before lymph flows into iliac nodes

  • Play a role in oncology staging for pelvic cancers

Clinical Significance

  • Oncology: Frequently involved in metastatic spread of cervical cancer, rectal cancer, and prostate cancer

  • Surgery: Important landmarks in pelvic exenteration and extended lymphadenectomy

  • Radiology: Detection on MRI or CT aids staging, prognosis, and treatment planning

  • Infection: Can be secondarily involved in pelvic inflammatory disease or tuberculosis

MRI Appearance

T1-weighted images:

  • Normal nodes show low-to-intermediate signal intensity

  • Fatty hilum (if present) shows bright signal intensity

  • No fluid: Nodes appear as solid structures against intermediate presacral fat (bright on T1)

T2-weighted images:

  • Nodes show intermediate-to-high signal intensity

  • Pathologic nodes (edematous, inflamed, malignant) show brighter signal

  • No fluid: Nodes remain intermediate; fat around sacrum appears bright

STIR (Short Tau Inversion Recovery):

  • Normal nodes: intermediate signal

  • Pathologic nodes (inflammation, metastasis): bright signal intensity

  • Fat signal suppressed, improving detection of abnormal nodes

T1 Fat-Sat Post-Contrast:

  • Normal nodes enhance mildly and homogeneously

  • Malignant nodes show heterogeneous or irregular enhancement

  • Necrotic nodes may show rim enhancement with central non-enhancing area

CT Appearance

Non-Contrast CT:

  • Nodes appear as soft tissue density in the presacral space

  • Fat planes help separate them from rectum and sacrum

  • Enlarged nodes appear as rounded soft tissue masses

Post-Contrast CT:

  • Normal nodes enhance mildly and uniformly

  • Malignant or inflamed nodes show irregular, heterogeneous enhancement

  • Necrotic or infected nodes demonstrate rim enhancement with central low attenuation

MRI image

Sacral lymph nodes MRI axial anatomy image-img-00000-00000

MRI image

Sacral lymph nodes MRI axial anatomy image-img-00000-00000_00002

CT image

Sacral lymph nodes CT axial anatomy image-img-00000-00000