M-MODE ULTRASONIC LOCALIZATION AND IDENTIFICATION OF FLUID-CONTAINING PULMONARY CYSTS

Successful ultrasonic localization of pleural fluid has been well documented in recent reports. The ability of ultrasound to detect and identify fluid within a parenchymal lesion has not been defined. We examined nine patients with cystic lesions and air-fluid levels noted on the chest roentgenogram. In all nine patients, an echofree space that corresponded anatomically to the level of fluid noted on the x-ray film could be recorded in the M-mode presentation. The combined thickness of the wall of the chest and the overlying lung as judged by ultrasound ranged from 2 to 8 cm, with a mean of 4 cm. The following two characteristics appeared to distinguish parenchymal from pleural fluid: (1) similar characteristics of motion of the proximal and distal interfaces of the sonolucent space; or (2) the ultrasonographic pattern of overlying lung proximal to the loculation of fluid. Ultrasonograms in eight (89%) of nine patients demonstrated one or both of these characteristics. These findings indicate that ultrasound can detect fluid within a parenchymal structure and may be used to differentiate intraparenchymal loculations from those in the pleural space.