Case #09 Discussion:

DIAGNOSIS: Superior vena cava thrombus

DISCUSSION: This patient presented with a venous thrombus in the SVC and was successfully treated with urokinase. The patient's symptoms of upper body swelling were consistent with an upper venous obstruction. This obstruction could be intra- or extraluminal. Extraluminal causes of obstruction would primary or metastatic carcinoma compressing the lumen extrinsically. The primary intrinsic obstruction is a thrombus. Other less common possibilities include trauma and radiation therapy.

The work-up of this patient included venography given the high index of suspicion for an intrinsic SVC clot (MR or CT would be the obvious choices to work-up a suspected extrinsic carcinomatous compression). Venography yields the benefits of being able to see the entire vascular anatomy including any collaterals that may have developed which would determine the need for surgery. It also allows a catheter to be placed for thrombolytic therapy. Once the catheter is in place, the patient can be easily followed up over fixed amounts of time without any further interventions. The drawbacks of venography include radiation exposure for the patient and some morbidity related to the procedure.

While venography remains the gold standard for evaluating venous obstruction, magnetic resonance venography has recently been used to analyze venous flow. It has been found to be 90% sensitive in evaluation of brachiocephalic clots and with gadolinium it can determine the obstructing mass to be bland vs. tumor. The obvious disadvantage is the inability to start therapy without gaining venous access as done in venography.

The patient was treated with urokinase at 120,000 U per hour with Heparin for 48 hours and showed complete resolution of the clot. UK causes plasminogen to become plasmin thereby causing fibrin to break down into fibrin degradation products and begin the process of systemic fibrinolysis. By delivering the drug directly in the area of the thrombus, clot resolution occurs quickly. UK is much more expensive than its counterpart, streptokinase, but has the significant advantage of not causing antigenic reactions. Other therapeutic options include venoplasty or venous graft bypass.