[Atelectasis caused by lung folding]

An atypical disturbance of ventilation supervening a pleural effusion may occur due to atelectasis by lung folding which is seen radiologically as a round image close to the chest wall with the appearance of a pseudo-tumour. The authors review the mechanisms and the clinical and radiological presentation of this disorder based on 7 cases and a review of the literature. The posterior basal type with adhesions to the chest wall are the most frequent. An intra-parenchymatous and a double-form are described. The diagnosis of this benign disorder is radiological. It is based on a characteristic displacement of the vessels and bronchi and associated pleural signs. Recognition of these signs avoids all invasive procedures.