Non-visualization of lung markings below hemidiaphragm in subtle subpulmonic effusion: an old sign resuscitated.

To assess the lack of visibility of vascular markings under the hemidiaphragm on a frontal chest radiograph as a sign of pleural effusion, fifteen patients were collected showing this sign. Pleural effusion was diagnosed by ultrasound, comparison with previous or subsequent chest x-ray or computed tomography. Patients in the study group exhibited this sign in the absence of the classical signs of pleural effusion. In the control group, lack of visibility of blood vessels was observed in only 4.2% cases. Non-visualization of vascular markings below the hemidiaphragm should alert the interpreter to the possible presence of pleural effusion and a lateral or decubitus view or ultrasound examination may be carried out to rule out effusion.