As you know many diseases causes pleural effusion such as cardiac diseases, nephrotic syndromes, malignancies and so on.
Its important for a physician to know the nature of pleural effusion . Is it transudate or exudates? The answer determines the differential diagnosis and treatment.
For years there has been no way except aspiration of the pleural fluid to discover what kind of effusion we have encountered.
This invasive method is unacceptable for many of the patients specialy in old age people because of their concomitant diseases and their concomitant medications.aspiration also has some important complications such as pneumothorax or probably infection.
In this study we introduce new method: Ultrasonography can offer an easier, less expensive and more acceptable method in this regard specialy in old age.
After selecting 80 patients(45 men and 35 women) that their pleural fluids had been aspirated and examined by lab,sonography was performed by two and expert radiologist separately. The radiologists had no clinical information concerning the patients and the result compared with lab results. Radiologists used this three criteria in determining the pleural effusion nature: 1)pleural effusion with septation 2) pleural effusion with echogenicity 3) thickening of pleura more than 3 mm.
Upon this study pleural effusion with septation or internal echogenicity are always exudates.Also sonographic evidence of a thickend pleura (more than 3mm) is highly suggestive of an exudates. Although an anechoic effusion is more probably the evidence of a transudate we have seen it in 14% of patient with exudates .In lab results we had 29 transudate and 51 exudate and in ultrasound results we had 34 transudate and 46 exudate. So ultrasound has 93% sensitivity and 86% specificity in diagnosing transudate and has 86% sensitivity and 93% specificity in diagnose of exudates.
We conclude that sonography is useful in determining the nature of pleural effusion.
Also sonography has the ability to show other finding associated with effusions such as metastasis to pleura, pleural nodules and some intra paranchymal lung lesions wich is more common in old age people and in this regard it has so much benefits for them than any other way.