CAN ULTRASOUND PREDICT THE NATURE OF PLEURAL EFFUSION?
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Objective: To assess the reliability of chest ultrasonography (US) in the evaluation of the nature of p,eural effusion (PE) as an alternative to diagnostic aspiration. Patients and Methods: Between October 2003 and February 2005, we prospectively analyzed the sonographic findings in 90 cases (63 males and 27 females) with PEs of various causes. Their ages ranged from 23 to 64 years (mean age = 39 years). Chest US was performed by one radiologist who was given no clinical information concerning the patients and four criteria were evaluated in determining the nature of Pa: echogenicity of pleural fluid, presence of septation, sonographic evidence of a pleural nodule and presence of associated parenchymal lung lesions. US guided needle drainage (thoracentesis) was done for all cases and the aspirated pleural fluid samples were sent for laboratory assessment and the nature of the effusions was established on the basis of chemical, bacteriologic, and cytological examination of pleural fluid; pleural biopsy; and clinical follow.-up. The sonographic results were compared with laboratory results as well as clinical follow up. Results: A total of 90 cases with PEs were studied. Twenty-one cases (23.3%) had transudates and 69 cases (76.7%) had pleural exudates. The final etiological diagnosis in cases with pleural exudates was achieved in 58 cases (84 %) and 11 cases (16 %) remained of unexplained etiology. The two types of effusions could be distinguished on the basis of sonographic findings in 87.7% of cases and in determining the etiology for pleural exudates, US diagnoses coincided with the final etiological diagnoses in 65.5% of cases. Most of the missed cases on US (11/20) were due to the abnormal echogenicity of pleural exudates having anechoic pattern suspected to be pleural transudates. Pleural trasudates were anechoic whereas pleural exudates could be echogenic or anechoic. PEs with septations, abnormal echogenicity, pleural nodules and associated parenchymal lung lesions were indicative of pleural exudates. PE with septations was seen in parapneumonic and tuberculous PEs. Homogenous echogenic pleural effusions were due to empyema or malignant effusion. The presence of pleural nodule was a specific finding for malignant PE. The complication rate of US guided thoracentesis was 2.2%. Conclusion: Chest US was found reliable in determination of the nature of PE. We suggest performing sonographic assessment of the pleural fluid in all patients with PE, as a routine examination and the sonographic patterns of PE must be correlated with the clinical data of the patient, available radiologic studies, laboratory investigations including blood chemistry as well as clinical follow-up.Thoracentesis should be performed only in suspicious and suitable cases in whom definitive diagnosis still needs laboratory assessment of the pleural fluid and US guided thoracentesis may be considered the best tool as it has very low complication rate.