Rounded Atelectasis

Etymology

• Derived from the Latin word rotundus, meaning “round,” and the Greek word atelectasis, meaning “incomplete expansion.” The term refers to a localized, round-like collapse of lung tissue associated with adjacent pleural disease.

AKA

• Folded lung syndrome
• Blesovsky syndrome

Definition

What is it?

• Rounded atelectasis is a localized form of lung collapse that appears as a round or oval mass-like opacity on imaging, typically associated with pleural thickening or fibrosis. It is benign and often related to chronic pleural diseases, such as asbestos exposure.

Caused by

• Chronic pleural inflammation or fibrosis, commonly due to:
  • Asbestos-related pleural disease
  • Tuberculosis
  • Empyema
  • Radiation therapy
  • Prior hemothorax
• Pleural effusions leading to folding or invagination of adjacent lung tissue

Resulting in

• A rounded or oval mass-like opacity on imaging
• Traction and invagination of lung parenchyma into the pleural thickening
• Associated volume loss in the affected area

Structural Changes

• Folding or invagination of lung parenchyma
• Thickened pleura adjacent to the affected area
• Traction bronchiectasis and vascular distortion

Pathophysiology

• Rounded atelectasis develops due to chronic pleural disease that causes localized scarring and contraction of the pleura. This leads to folding or invagination of the underlying lung tissue, which appears as a round or oval opacity on imaging. Traction from pleural fibrosis causes distortion of bronchi and blood vessels, creating the characteristic “comet-tail sign.”

Pathology

• Collapsed alveoli with folded lung parenchyma
• Associated pleural thickening or fibrosis
• Evidence of chronic inflammation and fibroblastic activity in the pleura

Radiology in Detail

CXR

Findings

• Round or oval mass-like opacity, often in the peripheral lung adjacent to pleural thickening
• Associated volume loss and possible displacement of adjacent structures

Associated Findings

• Pleural thickening or calcifications
• No mediastinal shift unless associated with significant volume loss

CT

Parts

• Lung parenchyma adjacent to thickened pleura

Size

• Varies but typically ranges from 2 to 5 cm in diameter

Shape

• Round or oval opacity with smooth or slightly irregular margins
• “Comet-tail sign” caused by distorted bronchi and vessels converging toward the mass

Position

• Commonly located in the lower lobes, particularly adjacent to areas of pleural thickening or effusion

Character

• “Comet-tail sign” caused by distorted bronchi and vessels converging toward the mass
• Adjacent pleural thickening or calcifications

Time

• Chronic process developing over weeks to months in the context of pleural disease

Associated Findings

• Possible subpleural atelectasis or pleural plaques

Other Imaging Modalities

MRI/PET CT/NM/US/Angio

• MRI: Rarely used but may confirm tissue characteristics and rule out malignancy
• PET-CT: Typically demonstrates low metabolic activity, helping differentiate from malignancy
• Ultrasound: Useful for detecting pleural effusion and guiding interventions

Key Points and Pearls

• Rounded atelectasis is a benign condition often associated with chronic pleural diseases, especially asbestos exposure.
• The “comet-tail sign” on CT is a hallmark feature, representing distorted bronchi and vessels.
• It is essential to differentiate rounded atelectasis from malignancy, particularly in patients with a history of asbestos exposure or smoking.
• Treatment typically focuses on addressing the underlying pleural condition if symptomatic; the lesion itself usually requires no intervention.
• Recognizing the imaging characteristics can prevent unnecessary biopsies or surgeries.