Extrapleural fat: description, incidence, and relation with body mass index

Pleural appendages (PA) are portions of extrapleural fat that hang from the chest wall. They have been described on videothoracoscopy, however their appearance, frequency and possible relationship with the amount of patient's fat remain unknown. Our aim is to describe their appearances and prevalence on CT, and determinate whether their size and number is higher in obese patients.

Axial images of 226 patients with pneumothorax on CT chest were retrospectively reviewed. Exclusion criteria included known pleural disease, previous thoracic surgery and small pneumothorax. Patients were divided in obese (BMI > 30) and non-obese (BMI < 30) groups. Presence, position, size and number of PA were recorded. Chi square and Fisher's exact test were used to evaluate differences between the two groups, considering p<0.05 as significant.

Valid CT studies were available for 101 patients. Extrapleural fat was identified in 50 (49.5%) patients. Most were solitary (n=31). Most were located in the cardiophrenic angle (n=27), and most measured < 5cm (n=39). There was no significant difference between obese and non-obese patients regarding the presence or absence of PA (p=0.315), number (p=0.458) and size (p=0.458).

Pleural appendages were seen in 49.5% patients with pneumothorax on CT. There was no significant difference between obese and non-obese patients regarding presence, number and size of pleural appendages.