Evolution of semi-rigid thoracoscopy

Pleural effusions despite being so common, there is no much literature available regarding definite diagnosis for pleural effusions. Application of Light's criteria changed the approach to pleural effusion and till date remains a very useful step in the diagnosis of pleural effusions. Pleural fluid biochemistry and adenosine deaminase (ADA) enzyme levels play a significant role in the diagnosis of tubercular effusion. Studies have shown that levels of ADA are more often higher in tubercular effusion than in any other cause for it. But ADA levels can also be elevated in other types of parapneumonic effusions (PPEs), especially complicated PPEs. Hence it is difficult to distinguish a tubercular pleural effusion (TPE) from other PPEs based on pleural fluid ADA levels alone. LDH/ADA ratio as an indicator for ruling out tuberculosis was analyzed in few studies with high sensitivity and specificity. The pleural fluid cytology has a varying sensitivity, with a maximum of only 60% and it may increase with subsequent tapping. Closed pleural biopsy using a Cope or Abrams needle has a sensitivity up to 80% in cases of tuberculous effusion and 40%-73% in cases of Malignancies. Semi-rigid thoracoscopy not only allows for visualization of the pleura but also helps in procuring the biopsies under direct visualization from the abnormal looking areas. In cases of primary pleural malignancies like mesothelioma, pleurodesis can also be done in the same setting after taking the biopsy, hence reducing the number of procedures. Limitation of the semi-rigid thoracoscopy is smaller sample size and more superficial sampling of the pleura. Cryobiopsy and Electrocautery guided pleural biopsy using the IT knife are the modifications in the semi-rigid thoracoscopy to overcome the drawback of smaller sample size. While navigation band image guided pleuroscopy helps in better visualization of the vasculature of pleura during the biopsy. Management of pleural effusions has evolved over a period of time. Starting with a single criterion based on pleural fluid proteins to semi-rigid thoracoscopy. The inexhaustible research in this field suggests the desperate need for a gold standard procedure with cost effectiveness in the management of undiagnosed pleural effusions. Semi-rigid thoracoscopy has revolutionized the management of undiagnosed pleural effusions, but it has its own limitations. Various modifications have been proposed and tried to overcome the limitations to make it a cost-effective procedure.