Superior vena cava obstruction

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

The superior vena cava is a thin-walled, low-pressure conduit carrying venous return from the head, neck, arms and upper thorax. A mediastinal tumour can compress or invade it, while central venous catheters and pacing leads create endothelial and flow disturbance that promotes thrombosis. Modern SVCO therefore includes malignant external obstruction, bland device-related clot and mixed tumour-thrombus disease. Lung cancer and lymphoma remain important malignant causes, but the exact histology matters because treatment response and the need for tissue differ substantially.

Symptoms reflect rate and level of obstruction and the development of collateral veins. Gradual narrowing may produce prominent chest-wall veins with modest symptoms because azygos and vertebral channels adapt. Rapid occlusion causes facial plethora, periorbital and neck swelling, upper-limb oedema, dyspnoea, cough, dysphagia and a feeling of head pressure, worse supine or on bending. Laryngeal oedema can threaten the airway; severe cranial venous hypertension can cause confusion or reduced consciousness. Haemodynamic shock is uncommon from SVCO alone and should trigger a search for tamponade, embolism or another emergency.

Contrast-enhanced CT of the chest and central venous system is the first-line stable-patient study. It defines whether compression, invasion or thrombus predominates, maps the obstruction and collaterals and identifies tumour, nodes and a safe biopsy site. Duplex ultrasound can confirm upper-limb and accessible central thrombus but cannot map the full mediastinal SVC. Catheter venography is the procedural reference for stent planning and permits pressure assessment, thrombus treatment and stent placement. In an undiagnosed stable patient, obtain tissue before radiotherapy or systemic therapy; poorly chosen empirical treatment can destroy lymphoma histology or commit the patient to the wrong cancer pathway.

Treatment is driven by severity and mechanism. Sit symptomatic patients upright, provide oxygen only for hypoxaemia and manage the airway early when swelling or stridor progresses. Endovascular stenting relieves pressure rapidly and is the preferred rescue for severe symptoms; it can also palliate obstruction while pathology and longer-term therapy are arranged. Bland thrombosis needs therapeutic anticoagulation when safe, sometimes with thrombectomy or thrombolysis in selected acute extensive disease. Chemotherapy or radiotherapy controls the underlying tumour according to histology, stage and sensitivity. Steroids have a limited, diagnosis-specific role and should not delay mechanical relief.

Key points

SVCO causes facial, neck and arm swelling, venous distension, breathlessness, cough and head pressure that often worsens when lying flat or bending forward.
Airway oedema, stridor, severe respiratory distress, confusion or reduced consciousness defines a decompression emergency; sit upright and involve airway and interventional teams immediately.
First-line anatomical investigation in a stable patient is contrast-enhanced CT of chest and central veins, which shows level, length, collaterals, thrombus, tumour and a tissue target.
Obtain histology before radiotherapy or systemic treatment when the patient is stable and no prior diagnosis exists, because lymphoma, small-cell lung cancer and other causes require different treatment.
Endovascular stenting provides the fastest reliable symptom relief and is preferred for severe or rapidly progressive obstruction, particularly when tissue diagnosis or tumour response will take time.
Anticoagulate confirmed catheter-associated or bland thrombosis when bleeding risk allows; decide line retention, removal and thrombectomy with oncology, haematology and interventional radiology.
Use tumour-directed chemotherapy or radiotherapy for durable control according to histology and stage; neither should be given empirically to every undiagnosed mediastinal mass.
Corticosteroids are not routine mechanical decompression and can obscure lymphoma histology; reserve them for a specific steroid-responsive tumour or associated airway or cerebral oedema after specialist discussion.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Thoracic malignancy

Lung cancer, lymphoma, mediastinal germ-cell tumour, thymic cancer and metastatic nodes can compress or directly invade the superior vena cava.

Intravascular device thrombosis

Central venous catheters, ports and pacing leads disrupt flow and endothelium, allowing thrombus to narrow the brachiocephalic veins or caval lumen.

Combined tumour and clot

Malignant compression slows venous flow and creates endothelial injury and hypercoagulability, so external narrowing and superimposed thrombosis often coexist.

Benign mediastinal disease

Fibrosing mediastinitis, large goitre, aortic pathology and other non-malignant masses are less common causes and require mechanism-specific treatment.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Upper venous pressure rises
Obstruction impedes return from head, neck, upper limbs and thorax, increasing hydrostatic pressure and producing oedema and venous dilatation.
2
Collateral channels recruit
Azygos, internal mammary, vertebral and chest-wall networks enlarge over time; gradual collateral development can make severe anatomical narrowing relatively well tolerated.
3
Airway tissues become oedematous
Venous congestion in pharynx and larynx can narrow the upper airway, especially when obstruction progresses quickly or collateral drainage is poor.
4
Cerebral drainage is impaired
Raised intracranial venous pressure causes headache and visual or cognitive symptoms; profound oedema and reduced cerebral perfusion can threaten consciousness.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Venous facial congestion

Periorbital or facial swelling, plethora and neck-vein distension that worsens supine or on bending is the characteristic upper-body pressure pattern.

Upper-limb involvement

Arm oedema, cyanosis, heaviness or venous dilatation may be bilateral centrally or asymmetric when catheter-associated brachiocephalic thrombosis predominates.

Collateral circulation

Dilated non-pulsatile veins over the upper chest and shoulder indicate chronic rerouting and help distinguish venous obstruction from acute allergic swelling.

Airway dangerRed flag

Voice change, dysphagia, stridor, tongue swelling, orthopnoea or rapidly increasing neck oedema requires senior airway and decompression planning.

Cerebral venous dangerRed flag

Severe headache, visual obscuration, confusion, syncope, seizure or reduced consciousness suggests critical cranial venous pressure.

Underlying thoracic cancer

Cough, haemoptysis, weight loss, lymphadenopathy or a mediastinal mass identifies a likely malignant driver but does not establish histology.

Red flags requiring action

Stridor, voice change, drooling, severe orthopnoea or facial and tongue oedema raises impending upper-airway compromise.
Confusion, agitation, severe headache, visual change, syncope or reduced consciousness suggests critical cerebral venous congestion or another neurological emergency.
Rapid symptom progression over hours or inability to lie flat requires monitored assessment and urgent decompression discussion.
Unilateral arm swelling, catheter dysfunction or neck and chest-wall collaterals may indicate device-associated thrombosis extending into the caval system.
Haemodynamic collapse is unusual in isolated SVCO and should prompt simultaneous assessment for tamponade, pulmonary embolism, tension pneumothorax and sepsis.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line contrast-enhanced CT chest and central veinsFirst stepFirst line
Why
Map obstruction, thrombus, collaterals and tumour and identify a biopsy route and other thoracic emergencies.
Interpretation and limitations
Use venous-phase timing and compare prior imaging; report level, length, near-total occlusion, azygos relation, bland versus tumour thrombus and airway or pulmonary compromise.
02
Duplex ultrasound of neck and upper limbs
Why
Detect accessible jugular, axillary or subclavian thrombosis and guide anticoagulation or line decisions.
Interpretation and limitations
A negative study does not exclude intrathoracic brachiocephalic or SVC obstruction, so CT remains necessary when the central syndrome is present.
03
Catheter venography
Why
Provide procedural definition and permit stenting, thrombectomy or pressure assessment.
Interpretation and limitations
This is the intervention-planning reference study rather than the usual first diagnostic test; access route and contrast burden require specialist review.
04
Histological tissue diagnosis
Why
Distinguish lung cancer, lymphoma, germ-cell, thymic and metastatic causes before tumour-directed treatment.
Interpretation and limitations
Choose the safest accessible node, mass or other site and preserve lymphoma architecture; defer only when life-threatening physiology requires immediate stenting first.
05
FBC, coagulation and renal profile
Why
Assess bleeding, cytopenia, contrast safety and readiness for anticoagulation, biopsy or endovascular therapy.
Interpretation and limitations
Thrombocytopenia and renal impairment modify but do not automatically prevent urgent intervention; discuss transfusion, contrast and anticoagulation strategy.
06
Echocardiography or pulmonary assessment when indicated
Why
Find tamponade, ventricular failure or pulmonary embolism when shock or breathlessness exceeds the caval pattern.
Interpretation and limitations
Do not label unexplained hypotension as SVCO alone; bedside imaging can reveal a second immediately treatable obstructive emergency.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Anaphylaxis or angioedema

Acute facial and tongue swelling with urticaria, wheeze or exposure history develops over minutes, unlike the venous collaterals and positional congestion of SVCO.

Heart failure or tamponade

Raised venous pressure and oedema occur with cardiac filling failure; echocardiography, lower-limb congestion and haemodynamics distinguish these and can identify a coexisting cancer emergency.

Upper-extremity deep-vein thrombosis

Isolated axillary or subclavian thrombosis causes predominantly unilateral arm swelling; central extension and bilateral head or neck features indicate more proximal obstruction.

Airway or pulmonary emergency

Pulmonary embolism, pleural effusion, central airway compression and infection cause breathlessness in cancer and may coexist, so CT must assess more than caval patency.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01TriageIdentify airway and cerebral dangerFirst stepFacial or upper-limb swelling and venous distension suggest central thoracic venous obstruction.

1Sit the patient upright, assess airway voice and stridor, breathing, circulation and cognition and establish monitoring and intravenous access outside a severely congested limb where possible.
2Call acute oncology and interventional radiology urgently; involve anaesthesia or critical care immediately for airway swelling, severe orthopnoea, syncope or neurological change.
3Obtain contrast-enhanced CT urgently if physiology allows, but do not make an unstable airway wait for a complete elective tissue sequence before decompression planning.

02Severe obstructionDecompress with an endovascular stentSVCO is severe, rapidly progressive or causing airway or cerebral compromise.

1Review CT and coagulation with the endovascular team and choose access, thrombus management and stent length while airway and resuscitation support continue.
2Deploy a self-expanding central venous stent across the obstructed segment and treat significant thrombus by the selected mechanical or pharmacological strategy when appropriate.
3Monitor immediate symptom response, bleeding, migration, rupture and re-occlusion and continue the diagnostic and tumour-control pathway after pressure relief.

03Stable undiagnosedSecure tissue before tumour therapyThe patient is physiologically stable and imaging shows a mediastinal tumour without established histology.

1Select the safest high-yield biopsy route with radiology, respiratory, haematology or surgery, preserving architecture and molecular material.
2Avoid empirical radiotherapy or corticosteroid exposure that may erase diagnostic lymphoma tissue unless a senior risk-benefit decision documents an urgent indication.
3Stage and treat the confirmed tumour with the relevant MDT, using chemotherapy, radiotherapy, immunotherapy or combined care according to biology and goals.

04ThromboticTreat clot and manage the deviceCT or ultrasound shows bland catheter-associated or upper central venous thrombosis.

1Start therapeutic anticoagulation when bleeding and platelet assessment permits, selecting agent around cancer site, renal function, interactions and procedures.
2Keep a functional necessary catheter when infection and mechanical failure are absent if the thrombosis pathway supports retention; remove or revise it when infected, unusable or no longer required.
3Discuss thrombectomy, thrombolysis or stenting for severe acute symptoms, threatened access or persistent central obstruction and define anticoagulation duration and follow-up.

Key medicines and prescribing safety3 treatments · regimens, roles and cautions

Prevents propagation and recurrent thrombosis when bland catheter-associated or tumour-related clot contributes to SVCO.

Therapeutic anticoagulation

Use the current cancer-associated thrombosis regimen at treatment dose, such as weight-based low-molecular-weight heparin or an appropriate direct oral anticoagulant, adjusted for renal function, platelets, bleeding site, interactions and planned biopsy or stenting.

Luminal gastrointestinal or genitourinary tumour, intracranial disease, thrombocytopenia, renal failure and urgent procedures alter choice and timing; anticoagulation cannot mechanically relieve fixed external compression.

May temporarily reduce inflammatory oedema or tumour bulk in selected presentations while definitive treatment is arranged.

Dexamethasone in selected oedema or steroid-responsive tumour

Use only the acute-oncology or lymphoma-specific specialist regimen when associated airway or cerebral oedema or a confirmed steroid-responsive tumour justifies it; there is no routine dose for all mechanical SVCO.

Steroids do not open a fixed caval obstruction and can compromise lymphoma diagnosis. Monitor glucose, infection, delirium and gastrointestinal risk and obtain tissue first whenever stable enough.

Provides durable shrinkage for responsive lymphoma, small-cell lung cancer, germ-cell tumour and other susceptible malignant causes.

Tumour-directed systemic therapy

Give the full histology- and stage-specific oncology regimen after adequate tissue, using the current protocol and organ-function modifications rather than an empirical generic SVCO schedule.

Clinical improvement takes longer than stent relief and initial tumour swelling or lysis can complicate therapy; preserve tissue and address immediate airway or cerebral danger first.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Upper-airway obstruction

Progressive laryngeal and pharyngeal oedema can make intubation difficult and cause hypoxic arrest without early airway and decompression planning.

Cerebral oedema

Severe cranial venous hypertension can produce headache, confusion, seizure, reduced consciousness and secondary impairment of cerebral perfusion.

Venous thrombosis and embolism

Catheter-associated or tumour-related clot can propagate, occlude upper-limb drainage, impair vascular access and occasionally embolise to the pulmonary circulation.

Stent or access complications

Endovascular treatment can cause bleeding, caval rupture, migration, re-occlusion, arrhythmia and contrast-related harm, requiring specialist selection and follow-up.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Trend facial and arm circumference or oedema, venous congestion, respiratory symptoms, ability to lie flat and neurological state during acute treatment.
After stenting, observe access site, haemoglobin, pressure, rhythm, chest pain, oxygenation and symptom relief and investigate recurrent swelling promptly.
During anticoagulation, monitor bleeding, platelets, renal function, interactions and planned procedures and confirm the intended duration and catheter plan.
Track tumour response and central patency through symptom review and disease-specific imaging rather than routine repeated venography in every stable patient.
Ensure pathology and molecular results remain owned after urgent stenting so decompression does not become the end of the cancer diagnostic pathway.
Provide an emergency return route for recurrent stridor, orthopnoea, confusion, syncope or rapidly increasing face and neck swelling.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Severity follows speed

A slowly narrowing cava can recruit extensive collaterals, while a smaller acute thrombotic change may cause dramatic symptoms before adaptation.

Shock needs another explanation

SVCO produces venous congestion more often than circulatory collapse, so look actively for tamponade, embolism, sepsis or airway hypoxia.

Stent buys diagnostic time

Rapid endovascular relief can stabilise severe symptoms while preserving the opportunity for tissue-directed cancer treatment afterward.

Steroids can erase lymphoma clues

Empirical corticosteroid before biopsy may cause lymphoid tumour regression and non-diagnostic tissue without relieving fixed mechanical narrowing.

Device and tumour can coexist

Do not stop at a catheter-associated clot when CT also shows external compression or malignant intraluminal invasion.

11Common pitfallsFrequent interpretation and management errors.

01
Laying a severely orthopnoeic patient flat for prolonged assessment before airway and decompression planning.
02
Calling all facial swelling an allergic reaction without examining venous collaterals and positional progression.
03
Starting radiotherapy or corticosteroid in a stable undiagnosed mediastinal mass before obtaining lymphoma-preserving tissue.
04
Using anticoagulation alone for critical fixed malignant compression with airway or cerebral compromise.
05
Attributing haemodynamic collapse to SVCO without assessing tamponade and pulmonary embolism.
06
Removing every central catheter automatically despite a functioning needed device and no infection.
07
Failing to resume pathology, staging and definitive tumour care after a successful stent.