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    Related Topics

    From Lymphatic System

    Lymphatic Collecting Vessels
    Carry lymph through lymph nodes.
    Mesenteric Lymph Nodes
    Drain the intestines and abdominal structures.
    Axillary Lymph Nodes
    Drain the upper limbs and chest wall.
    Posterior Mediastinal Nodes
    Drain posterior thoracic structures.
    Lymphatic Capillaries
    Initial lymphatic vessels that collect interstitial fluid.
    Retroaortic Nodes
    Located behind the aorta.
    Jugular Trunk
    Drains lymph from the head and neck.
    Anterior Mediastinal Nodes
    Drain anterior thoracic structures.
    Occipital Lymph Nodes
    Drain the back of the scalp.
    Peyer’s Patches
    Lymphoid nodules in the small intestine.
    Thoracic Duct
    Main lymphatic duct draining most of the body.
    Bronchomediastinal Trunk
    Drains lymph from thoracic organs.
    Tracheobronchial Nodes
    Drain lungs and bronchi.
    SALT
    Skin-associated lymphoid tissue.
    Spleen
    Filters blood and initiates immune response.
    BALT
    Bronchus-associated lymphoid tissue.
    Supraclavicular Lymph Nodes
    Located above the clavicle; key in thoracic drainage.
    Submandibular Lymph Nodes
    Drain the face, mouth, and pharynx.
    Mastoid Lymph Nodes
    Drain the posterior scalp and ear.
    Pectoral Axillary Nodes
    Located along the anterior chest wall.
    Red Bone Marrow
    Produces lymphocytes; site of B-cell maturation.
    MALT
    Mucosa-associated lymphoid tissue.
    NALT
    Nasal-associated lymphoid tissue.
    Submental Lymph Nodes
    Drain the floor of the mouth and central lower lip.
    Pharyngeal Tonsil
    Located in the nasopharynx (adenoids).

    Sacral Lymph Nodes

    Reviewed by our medical team

    Drain the pelvic floor and rectum.

    1. Overview

    The sacral lymph nodes are a small group of deep lymph nodes located in the pelvic cavity, adjacent to the sacrum. Although limited in number and often overlooked in physical examinations, they serve a critical role in draining lymph from deep pelvic structures such as the rectum, posterior pelvic wall, and parts of the uterus and vagina. They are part of the deep pelvic lymphatic network and play an important role in cancer staging, especially in rectal and gynecologic malignancies.

    2. Location

    The sacral lymph nodes are located in the concavity of the sacrum, posterior to the rectum. They lie near the middle sacral vessels and are typically positioned in the presacral space, between the sacrum and the pelvic viscera. These nodes are not accessible by palpation and are only visualized through imaging or during surgical procedures.

    They receive afferent lymphatic drainage from:

    • The posterior pelvic wall

    • Lower rectum and anal canal (posterior portion)

    • Portions of the cervix, uterus, and vagina

    Their efferent lymphatic vessels drain into the common iliac lymph nodes.

    3. Structure

    Each sacral lymph node is a small, encapsulated structure composed of highly organized lymphoid tissue. Structurally, they consist of:

    • Capsule: A connective tissue covering that supports and protects the node.

    • Cortex: Contains follicles rich in B lymphocytes that are involved in humoral immune responses.

    • Paracortex: Contains T lymphocytes and dendritic cells that mediate cellular immunity.

    • Medulla: Contains plasma cells, macrophages, and medullary sinuses that filter lymph.

    Lymph enters via afferent vessels, percolates through the cortex and medulla for filtration, and exits via efferent vessels that continue toward the common iliac nodes.

    4. Function

    The primary functions of the sacral lymph nodes include:

    • Filtration of lymph: Removing pathogens, tumor cells, and debris from lymph originating from pelvic structures.

    • Immunological surveillance: Facilitating immune recognition of antigens in lymph from posterior pelvic organs.

    • Lymphatic relay: Acting as intermediate nodes in the drainage pathway from pelvic organs to the central lymphatic system.

    5. Physiological Role(s)

    Despite their small size and deep location, sacral lymph nodes serve several important physiological roles:

    • Protection against pelvic infections: They help trap and respond to infections in the lower rectum, posterior uterus, and posterior pelvic wall.

    • Tumor surveillance: They monitor lymph for malignant cells, especially from colorectal and gynecological cancers.

    • Drainage of pelvic lymph: They assist in returning filtered interstitial fluid from the pelvic cavity to the venous system via the lymphatic network.

    6. Clinical Significance

    Lymphadenopathy

    Sacral lymphadenopathy is rare and not usually apparent on physical examination due to the nodes’ deep location. When enlarged, it is typically detected via imaging modalities. Causes may include:

    • Rectal or anal infections

    • Pelvic inflammatory disease (PID)

    • Tuberculosis affecting pelvic organs

    Malignancy and Cancer Staging

    Sacral lymph nodes can be involved in the metastatic spread of several pelvic cancers, including:

    • Rectal and anal canal cancers — especially posterior and lower portions

    • Cervical cancer

    • Endometrial and vaginal cancers

    • Prostate cancer — rarely, through accessory drainage pathways

    Their involvement often signifies advanced disease and can alter surgical planning and prognosis.

    Imaging and Diagnosis

    Because sacral lymph nodes are not externally visible or palpable, diagnostic evaluation relies on imaging, such as:

    • MRI: Useful for identifying enlarged nodes, especially in rectal cancer staging (TME planning).

    • CT scan: Often included in abdominal/pelvic staging protocols.

    • PET-CT: Detects metabolically active nodes in oncology patients.

    Surgical and Oncologic Considerations

    During oncologic resections such as abdominoperineal resection (APR) or pelvic lymphadenectomy, sacral lymph nodes may be assessed or removed. Their involvement may require broader excision and adjuvant therapy (e.g., chemotherapy or radiation).

    Postoperative Complications

    • Lymphocele formation: May occur when efferent vessels are disrupted.

    • Pelvic lymphedema: Rare but possible with extensive node removal.

    Did you know? The lymphatic system helps the body combat infections by filtering out bacteria and other pathogens from lymph.