Makindo Medical Notes

Related Subjects: |Hypercalcaemia |Neutropenic Sepsis |Pulmonary Embolism |Lung Cancer |Superior vena caval obstruction syndrome |Cerebral Metastases |Metastatic bone disease |Oncological emergencies

Superior vena caval obstruction syndrome develops in 5-10% of patients with right-sided malignant intrathoracic mass lesions. Early recognition and treatment are crucial to preventing serious complications.

About

• Superior Vena Cava (SVC) Obstruction: This condition occurs when the superior vena cava, the large vein carrying blood from the head, neck, arms, and upper chest to the heart, is obstructed.

Aetiology

• SVC obstruction impedes venous return from the upper body, leading to congestion and increased pressure in veins above the blockage.
• The SVC has a thin wall and is easily compressed due to the low pressure inside it, making it vulnerable to external compression by nearby structures.
• It lies adjacent to the upper lobe of the right lung and within the mediastinum, making it susceptible to compression from mediastinal masses.
• Approximately 85% of cases are caused by lung cancer or other malignancies such as lymphoma.

Causes

• Malignancy: Lung cancer (especially right-sided), lymphoma, or metastatic disease are the most common causes.
• Venous thrombosis: Thrombosis related to venous catheters, pacemakers, or peripherally inserted central catheters (PICC lines) can also cause SVC obstruction.
• Mediastinal fibrotic diseases: Conditions causing fibrosis in the mediastinum can lead to SVC obstruction.
• Vascular abnormalities: Aortic aneurysm or arteriovenous (AV) fistula may also compress the SVC.
• Infections: Infectious diseases like histoplasmosis, tuberculosis (TB), and syphilis can result in SVC obstruction through mediastinal involvement.
• Pediatric considerations: In children, non-Hodgkin's lymphoma is a common cause of SVC obstruction.

Clinical Features

• Common presenting symptoms include facial swelling, shortness of breath (dyspnoea), and a persistent cough.
• Severe cases may involve tracheal obstruction, causing difficulty breathing and wheezing.
• Physical examination may reveal dilated neck veins and visible collateral veins on the anterior chest wall.
• Symptoms often worsen when the patient raises their arms above their head (Pemberton's sign).

Investigations

• Blood Tests: Full blood count (FBC), urea and electrolytes (U&E), liver function tests (LFTs), C-reactive protein (CRP), calcium, and alkaline phosphatase (ALP) may assist in evaluating the patient's overall condition.
• Chest X-ray (CXR): May show widening of the superior mediastinum; 25% of patients with SVC syndrome also have a right-sided pleural effusion.
• Sputum Cytology: Can help identify the underlying malignancy.
• CT Scan: The diagnostic modality of choice for visualizing the obstruction and planning biopsy if necessary.
• Invasive Contrast Venography: The most conclusive diagnostic test to directly visualize the obstruction in the SVC.

Pathology

• The majority of cases of SVC syndrome are caused by malignancy, most commonly lung cancer or lymphoma, which directly compress or invade the SVC.

Management

• Initial Management: Airway, breathing, circulation (ABC) support, oxygen administration, and elevating the patient's head can provide symptomatic relief.
• Steroids: Corticosteroids may be considered to reduce inflammation and swelling in certain cases.
• Radiation Therapy: This is the treatment of choice for non-small-cell lung cancer causing SVC syndrome.
• Chemotherapy: Used in conjunction with radiation for small-cell lung cancer and lymphoma, as it is effective in shrinking the tumour causing the obstruction.
• Venous Stenting: Symptoms recur in 10-30% of cases, and venous stenting can be a palliative option to restore venous flow.
• Thrombosis Management: If a central catheter is causing the obstruction, it should be removed, and anticoagulation therapy initiated to manage the clot.

References