Opacification of portions of liver parenchyma (usually medial segment, quadrate lobe) through collaterals
Hot quadrate sign: Avid enhancement of left medial segment of liver on arterial phase (not seen on venous or delayed phases) due to intra- and perihepatic collaterals
PATHOLOGY
• > 75% of cases due to malignancy
Lung cancer and lymphoma most common causes
• Other etiologies
Thrombosis due to hypercoagulable state, long-term indwelling SVC catheter, or pacemaker
Infectious lymphadenopathy from histoplasmosis, tuberculosis, coccidiomycosis
Autoimmune or postradiation mediastinal fibrosis
Fibrosing mediastinitis
CLINICAL ISSUES
• Symptoms vary based on rapidity of obstruction
• Patients with cerebral edema or airway obstruction (due to stridor) must be treated emergently
SVC stent placement ± radiation therapy
• Remove catheter and anticoagulation for catheter-related thrombus ± catheter-directed thrombolysis
DIAGNOSTIC CHECKLIST
• Utilize coronal MIP imaging to identify collateral veins
(Left) Coronal CECT in an elderly woman who presented with a puffy face demonstrates obstruction of the superior vena cava (SVC) , with collateral flow through an enlarged azygous vein as well as various mediastinal collateral veins .
(Right) Axial CECT in the arterial phase in a patient with malignant SVC occlusion demonstrates a wedge-shaped perfusion abnormality in the left medial segment of the liver (hot quadrate sign) and collateral veins over the surface of the liver.
(Left) Axial CECT in a young woman evaluated for aortic dissection shows near-complete occlusion of the SVC with extensive collateral veins over the chest and abdominal walls.
(Right) Axial CECT in the same patient shows a segment of dense parenchymal enhancement in the medial segment of the liver due to opacification of liver parenchyma alongside the intra- and perihepatic collaterals . The liver perfusion abnormality was not seen on portal venous phase images (not shown).
TERMINOLOGY
Abbreviations
• Superior vena cava (SVC) obstruction
Synonyms
• Superior vena cava (SVC) syndrome
Definitions
• Occlusion of SVC by extrinsic compression, tumor invasion, or intrinsic thrombus
IMAGING
General Features
• Best diagnostic clue
Mediastinal lymphadenopathy, masses, or calcifications with non-visualized SVC and multiple venous collaterals
• Location
Superior mediastinum
• Size
Mass 5-10 cm
Imaging Recommendations
• Best imaging tool
CECT
• Protocol advice
Bolus IV injection of contrast medium
Multiplanar reformations (including maximum-intensity projection reconstructions) to display venous collaterals
CT Findings
• CECT
Buy Membership for Radiology Category to continue reading. Learn more here
Dilated collateral veins (internal jugular veins, intercostal veins, azygous vein, lateral thoracic, etc.)
, with collateral flow through an enlarged azygous vein 
as well as various mediastinal collateral veins 
.
in the left medial segment of the liver (hot quadrate sign) and collateral veins 
over the surface of the liver.
with extensive collateral veins 
over the chest and abdominal walls.
due to opacification of liver parenchyma alongside the intra- and perihepatic collaterals 
. The liver perfusion abnormality was not seen on portal venous phase images (not shown).
