What is, by far, the most common cause of vena cava superior syndrome?
Occlusion of the vena cava superior by mediastinal tumorous growth.
What would clinical symtpoms such as facial and/or neck swelling, flushing and dyspnoea suggest about the underlying cause?
Rapid growth of the occluding tissues. In cases with slower onset there tends to be time for development of collateral vessels, and patients might be asymptomatic even with extensive occlusion.
Which is the most important vessel for potential collateral blood flow in case of occlusion of the superior vena cava ?
The azygos vein.
What is the patophysiologic explanation of hepatisation of the lung?
Effusion of liquid into the airways, rendering the lung impervious to air.
The tumor in the right upper lobe is now significantly larger with direct growth into the upper mediastinum. The superior vena cava is engorged and almost completely obstructed by surrounding tumorous tissue, which also obstructs the azygos vein. Enlarged, contrast-filled venous collaterals are seen in the right anterior thoracic wall. The findings are consistent with superior vena cava syndrome grade IV.
The right main bronchus is completely occluded by tumorous tissue. Subsequently, there is no ventilation of the right lung, which appears low attenuating with a density roughly corresponding to fluid. Multiple contrast-enhancing lesions in the right lung parenchyma consistent with metastases. The left lung is adequately ventilated with several densities suspicious of parenchymal and pleural metastases. Bilateral pleural effusions.
In the upper abdomen, there is heterogeneous contrast enhancement of the liver (probably due to the early contrast phase) with at least one metastatic lesion present in segment 4. The metastasis of the left adrenal has increased in size.
Please note the appearance of the right lung on the topogram. If this patient had been examined with a plain chest radiograph, chances are that such a study would have been interpreted as a massive right pleural effusion.