SVC Obstruction

The final podcast in the new Podmedics oncology series. In this podcast we look at the rare but important emergency of superior vena cava obstruction.

 

Video Duration: 4 minutes

  • SVC Obstruction
    Created by How curious.
    General
    Epidemiology

    Obstruction of the superior vena cava causing interrupted venous return from the head, thorax and upper extremities into the right atrium.

    65% of cases are caused by malignancy. Most common malignant causes are:

    • lung cancer
    • non-Hodgkin's lymphoma.

    Malignant causes affect males > females. Middle-aged to elderly men are more commonly affected by malignant causes of SVC obstruction.

    Benign causes: males = females. More common in younger people.

    Infectious causes (e.g. syphilitic aortic aneurysm, TB) used to be very common; now very rare.

    Pathology

    The SVC has a thin wall and can be obstructed by intraluminal, mural or extrinsic factors.

    Slowly progressive SVC obstruction (i.e. several weeks - months) can allow the formation of collateral circulation to drain the venous flow. This happens via the azygous and internal mammary venous systems mainly, but also the long thoracic venous system leading to the femoral and vertebral veins.

    Acute SVC obstruction is often a medical emergency.

    SVC obstruction usually increases the cervical venous pressure to 20 - 40 mmHg, where the normal pressure is 2 - 8 mmHg.

    Top three causes
    1. Small & non-small cell lung carcinoma & Non-Hodgkin's lymphoma (~76%)
    2. Other malignant causes
    3. Non-malignant causes (e.g. mediastinal fibrosis, vascular disease, infections, pacemaker/implantable defib. ..)
    Clinical Features
    Symptoms

    Minor symptoms and signs are often overlooked, but patients may complain of the following symptoms.

    Common symptoms:

    • dyspnoea
    • swollen face/neck/upper extremities (due to oedema)
    • facial plethora
    • cough
    • distended neck (63%)/chest (53%) veins
    • hoarse voice
    • lymphadenopathy

    Uncommon:

    • blurred vision
    • stridor
    • confusion/stupor

    Patients often also have anorexia, some weight loss and haemoptysis, though these symptoms are much less specific.

    Signs

    Characteristic findings:

    • venous distension of the neck and chest wall
      • usually worse on bending forwards
      • veins on the chest wall are due to prominent collateral circulation
    • facial oedema
    • upper extremity oedema
      • patients often look very swollen from the nipple upwards! This can be uncomfortable.
    • plethora
      • due to venous engorgement and oedema
      Investigations
      Cultures

      None

      Bloods

      ESR & CRP - elevated in patients with infection or immunological disorders.

      Imaging
      1. CXR!
        • This is really important to try to see if there is an obvious widening of the mediastinum or a visible lesion in the lung that could be the cause of the obstruction.
      2. Chest CT
        • To help determine the extent of the obstruction (e.g. full or partial), collateral circulation development, location etc.
      3. Chest MRI
        • (as for CT)
      4. Ultrasound scan
        • Non-invasive.
        • To identify/exclude presence of thrombus, visualise SVC dilatation and loss of respiratory variation.
      Scopic/Biopsy

      Consider a biopsy of the tumour to confirm the presence of malignancy in a new patient with no cancer diagnosis.

      Functional

      None

      Treatment
      Conservative

      None

      Medical

      In patients with ongoing SVC obstruction (i.e. not acute) with a malignant cause:

      1. Treat the malignancy
        • Most tumours causing SVC obstruction are radiotherapy sensitive
        • Chemotherapy and surgical resection are other options, but selection of therapy depends on a number of factors such as type of malignancy, staging and histopathology results.
      2. Palliative therapy
        • Radio-/chemotherapy, corticosteroids, stents.
        • Support the patient: diuretics, low-salt diet, head elevation, oxygen.
        Surgical

        None