Hello!I can understand your concern. It is necessary to aspirate some of the collected fluid from the chest and analyse it . Once analysed with the battery of tests, the cause for the fluid collection (medically called pleural effusion) can be ascertained. Accordingly the appropriate treatment needs to be initiated. Though past history of TB increases the chance that this time too it could be TB again, but not necessarily so . So consult a pulmonologist and get treated appropriately . All the govt medical college hospitals in kolkata have a separate Pulmonary Medicine dept , where you can get to consult pulmonologists (doctors specialised in all chest diseases including TB). Wish your brother a speedy recovery . Hope my reply helps. Do drop in your valuable feedback.