Observations on the pathogenesis of pleural effusions

1. Factors which affect fluid accumulation within the pleural cavities have been discussed, particular emphasis being laid on the derangement in the handling of protein which may occur at serous surfaces.2. A method of e- timating albumin turnover in serous effusions has been described.3. Forty -two patients, whose diagnoses had been established, were included in the investigation. The evidence for the diagnosis in each case has been presented in detail and a clinical report on each patient has been given in .Appendix A.4. The diagnostic groups examined were; tuberculosis, pulmonary embolus, lung carcinoma, secondary carcinoma and congestive cardiac failure. In each group the rate of albumin entry into, and loss from, the pleural cavity has been estimated and the results expressed individually and collectively. These have shown that the rate of albumin loss tended to use low in all conditions other than pulmonary embolism. In pulmonary embolism, where no significant reduction in this value is thought to exist, the rate of albumin loss bore a direct relationship to effusion volume.In some instances, the change in the albumin turnover pattern following intrapleural prednisolone administration was also measured. These results have been expressed in grams albumin entering or leaving the pleural cavity in 24 hours. The mean results of each group have also been expressed in mg./kg./hour albumin and the "effusion fluid" loss in ml./kg./hour. The rate of albumin entry has been found to fall fairly consistently following prednisolone administration.The response in the rate of albumin loss has been more variable and this has been attributed to three factors:(1) the volume of the effusion, (2) the degree of reversibility of any inflammatory condition of the parietal pleura, if present, (3) a corticosteroid affect in reducing lymphatic capillary permeability.5. x patient with malignant granulosa cell tumour of the ovary associated with ascites and a right pleural effusion has also been investigated. The results, which are thought to apply to Meigs' syndrome, demonstrated that a very large amount of albumin was leaking into,he ascites and some of this en route to the blood vascular system spilled into the right pleural cavity presumably from either the diaphragmatic or mediastinal lymphatics.6. The known pathology of the various conditions, as it is likely to affect the pleural space, has been reviewed and the results of the investigations correlated with it.7. It has been suggested that there is a diagnostic application of the method when routine clinical, bacteriological, biochemical and histological investigations have failed to secure the diagnosis.8. The method has been shown to be particularly applicable to a study of the importance of certain capillary permeability factors in diseases associated with ascites and pleural effucion.9. Finally, in u light of the findings, the present nomen- clature of pleural effusions has been discussed and certain recommendations made regarding the definition of the terms "exudate" and "transudate "