Prevalence and characteristics of pleural effusions in superior vena cava syndrome

The prevalence and characteristics of pleural effusions occurring in adults with the superior vena cava (SVC) syndrome are unknown. The purpose of the present study was to characterize these pleural effusions.

Charts of patients diagnosed with SVC syndrome at a tertiary care referral centre were reviewed. Radiographs were evaluated for the presence and size of pleural effusions, presence and location of masses and mediastinal width. If a pleural effusion was present, the patient's chart and a pre-existing database on pleural effusions were searched to determine whether the effusion was sampled and the results of any laboratory investigations on the fluid.

The SVC syndrome occurred in 78 patients. Malignancy was the aetiology in 60% of the cases and bronchogenic carcinoma was the most common malignancy. An intravascular device was the aetiology in the majority of benign cases. Pleural effusion was found in 70% of patients with a malignant aetiology and 58% of those with a benign cause (P=0.345). The mean size of the effusions was larger in malignant cases (P=0.012). Of the 44 effusions 22 were sampled (17 in malignancy and five with benign processes); none was transudates, 20 (91%) were exudative (four of these were chylous) and the remaining two were reported as exudates but did not have pleural chemistries documented.

More than half of patients with SVC syndrome have pleural effusions, regardless of the aetiology. However, the effusions are larger when associated with malignancy. The majority of these effusions are exudative and occasionally chylous. None was transudates.