Chest Imaging

Apical cap

a curved radiographic opacity frequently identified in the apex of one or both lungs, in the concavity formed by the first and second ribs. The commonest pathological finding is a nonspecific fibrous scarring of apical lung parenchyma, which merges with the visceral pleura. The frequency of this scarring increases significantly with age. The lower border of the apical cap interface with normal lung is irregular and ill defined. Such opacities should be considered abnormal only if they are thicker than 1 cm, or asymmetrical, or associated with bone abnormality such as lysis of the first ribs or vertebra, or are associated with chest pain. In these circumstances, further investigations including CT, MRI or percutaneous biopsy is required (see percutaneous biopsy thoracic). The differential diagnosis includes mycobacterial infections (tuberculosis, atypical mycobacterial infection), actinomycosis, or lung cancer (Pancoasts neoplasm).

Apical cap may appear as a well-defined opacity with a smooth lower margin that may also be seen in a variety of disorders. In the case of trauma, it may represent extrapleural dissection of blood from a rupture of aorta, rib fractures, or haemorrhage secondary to subclavian catheter placement. Other causes include vascular causes and mediastinal lipomatosis.

PG