The value of inspiratory-expiratory lateral decubitus views in the diagnosis of small pleural effusions

AIM: To evaluate the usefulness of expiratory lateral decubitus views in the radiological diagnosis of small pleural effusions. MATERIALS AND METHODS: Patients referred for abdominal sonography for various reasons were examined for ultrasonographic features of pleural effusion. From November 1994 until May 1996, 36 patients were found to have pleural effusion not exceeding 15 mm in depth and were included in the study. Erect posteroanterior, lateral, and lateral decubitus (in inspiration and expiration) ragiographs were performed in all patients. RESULTS: The mean thickness of fluid was 4.3 mm on inspiratory lateral decubitus radiographs and 7.9 mm on expiratory lateral decubitus views (P < 0.005). In 31 of 36 patients (86%) there was a difference in the thickness of the fluid layer as measured in expiratory vs. inspiratory lateral decubitus radiographs. In 16% of patients, the fluid was not visible on inspiratory lateral decubitus projections. CONCLUSIONS: Expiratory lateral decubitus views may be useful for demonstrating small pleural effusions.