Inferior vena caval (IVC) thrombosis is an essential diagnosis while evaluating any neoplastic lesion, or portal hypertension. It is also important to differentiate bland thrombus from tumour thrombus.
Patient can present with many features which include
IVC thrombus can be classified under two broad headings:
- bland thrombus
- tumour thrombus
On all imaging, they appear as persistent filling-defect within IVC. Chronic thrombosis can lead to peri-caval and peri-aortic collateral formation 1.
Bland thrombus can be an isolated thrombus. However, it is commonly arising from deep vein thrombosis of lower extremities.
- hypercoagulable states
- venous stasis
- compression by neoplastic lesions, lymph nodes, retroperitoneal masses/fibrosis or haemorrhage
- foreign bodies: vena cava filter, catheters
- extension from benign tumours: angiomyolipoma, IVC leiomyoma, adrenal pheochromocytoma
- traumatic liver injury: very rare 4
While any neoplastic lesion can cause IVC thrombosis, renal cell carcinoma is the most common malignancy to extend into IVC 1. Other tumours that have a tendency for IVC thrombosis are hepatocellular carcinoma, adrenocortical cancer and Wilm's tumour, primary leiomyoma or leiomyosarcoma of the IVC.
It is important to characterise the thrombus from RCC for surgical management.
According to TNM classification of RCC, tumour spread into infradiaphragmatic IVC is T3c stage, while extension in supradiaphragmatic IVC is T4b stage. Also, subclassification into infrahepatic, hepatic and suprahepatic extension can further help the surgeon.
Differentiating bland and tumour thrombus
- a bland thrombus results from external compression of the IVC by a neoplastic lesion (i.e no direct invasion), so the IVC is usually narrowed at the site of thrombosis. In contrast, tumour thrombus expands the IVC
- tumour thrombus will often show continuity with primary tumour
- in arterial phase, neovascularity may be appreciated in tumour thrombus
Conditions that may mimic thrombus include
- pseudothrombosis caused by laminar flow of enhanced blood from renal veins streaming parallel to column of unopacified blood returning from lower body; delayed images will show resolution of filling defect
- pseudolipoma (paracaval lipoma) is the partial volume artefact due to pericaval fat above caudate lobe, seen commonly in patients with chronic liver disease; coronal reformats usually clear the doubt 2
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