Apical pulmonary opacity

What it means

An apical cap is a caplike lesion at the lung apex, usually caused by intrapulmonary and pleural fibrosis pulling down extrapleural fat or possibly by chronic ischemia resulting in hyaline plaque formation on the visceral pleura. The prevalence increases with age. It can also be seen in hematoma resulting from aortic rupture or in other fluid collection associated with infection or tumor, either outside the parietal pleura or loculated within the pleural space.

The usual appearance is of homogeneous soft-tissue attenuation capping the extreme lung apex (uni- or bilaterally), with a sharp or irregular lower border (See Figure 6 of PMID:18195376). Thickness is variable, ranging up to about 30 mm. An apical cap occasionally mimics apical consolidation on transverse CT scans.

Rare diseases that can present with this1

The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions. A sign on this page is a conversation to have with a clinician, not a conclusion.

Part of the broader category

Also called: Apical cap · Apical pleural thickening