Unilateral hyperlucent lung: the case for investigation.

Seventeen children with unilateral hyperlucent lungs were referred for investigation. Of the 11 who had a referring diagnosis of possible Macleod's syndrome only two were shown to have post-viral bronchiolitis. Three of the 11 had conditions that required surgical treatment and a further two with brochiectasis were treated medically. To avoid confusion we suggest that Macleod's syndrome is reserved exclusively for children with post-viral bronchiolitis. Radioisotopic regional lung function studies were useful in the investigation of the subjects from three points of view. Firstly, they distinguished children with primary perfusion abnormalities and normal ventilation, secondly, they defined the extent of altered respiratory function, and thirdly, they were able to distinguish compensatory emphysema from congenital lobar emphysema. As bronchography and bronchoscopy may be hazardous in small children with poor respiratory reserve, such regional studies may be useful in indicating which patients do not require further invasive investigation.