Case of the Week: October 1-October 8, 2010

38-year-old man with atypical chest pain and shortness of breath

What are the pertinent radiologic findings? What is your differential diagnosis? What is your favorite diagnosis?

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Case Details

PA (Fig. 1A) and lateral (Fig. 1B) chest radiographs demonstrate a hyperlucent right hemithorax with a paucity of vascular markings. On closer inspection, multiple cystic-like lesions are seen throughout the right hemithorax and in the left apex to a lesser degree. The horizontal fissure is not displaced and lies in its normal anatomic position and contacts the lateral chest wall at the level of the 5th anterior rib. There is minimal contralateral displacement of the cardiomediastinal silhouette and the ipsilateral diaphragm is not flattened or inverted. No distinct visceral-parietal pleural reflection is identified. There is significant relaxation atelectasis of the remaining right lower lung. Axial (Fig. 2A-F) and coronal MIP (Fig. 3A-D) chest CT images reveal that at least two-thirds of the right lung has been replaced by large coalescing bulla which trap air and compress the adjacent relatively normal preserved lung parenchyma with resultant ipsilateral volume loss. The bulla are primarily subpleural but also located in the lung parenchyma. Smaller such bullous lesions are also seen in the left upper lobe. Scant foci of centrilobular emphysema can also be seen in the left upper lobe.

Answer

Diagnosis: Giant Bullous Emphysema (Vanishing Lung Syndrome)

Differential Diagnosis Unilateral Hyperlucent Thorax

  • Incorrect Radiographic Centering / Rotation / Grid Cut-Off
  • Chest Wall Abnormalities
    • Modified Radical Mastectomy
    • Various Muscle Flap Transpositions used in Reconstructive Head and Neck Surgery
    • Poland Syndrome
  • Altered Lung Perfusion
    • Central Pulmonary Embolus
    • Swyer-James Syndrome
    • Pulmonary Artery Hypoplasia
    • Congenital Lobar Emphysema
  • Central Bronchial Obstruction
    • Primary Endobronchial Lesions
    • Secondary Endobronchial Lesions
    • Obstructing Foreign Bodies
    • Extrinsic Compression of Central Bronchus (e.g., tumor; lymphadenopathy; mediastinal mass)
  • Emphysema
  • Pneumothorax

Discussion

Bullous emphysema refers to the presence of emphysema associated with large bulla. It is typically seen in patients that have centrilobular emphysema, paraseptal emphysema, or both. Giant bullous emphysema (GBE) also referred to as primary bullous emphysema or vanishing lung syndrome, is characterized by bulla occupying at least one third of the hemithorax.  Giant bullae form when adjacent areas of paraseptal emphysema coalesce, and are therefore usually subpleural in distribution. Bullae are described as air-filled spaces exceeding 1cm in size with a wall thickness less than 1mm. It was originally hypothesized that bulla formation was due to a “ball-valve mechanism” in which gas entered the lesion but could not exit. Over time, the bullae would enlarge with subsequent destruction and compression of adjacent lung parenchyma. Newer research, however, suggests there is negative intra-bullous pressure, similar to pleural pressure, and is thus preferentially ventilated during inspiration with loss of elastic recoil preventing air from being expelled.  Giant bullae usually form in areas of parenchymal weakness, tends to preferentially affect the upper lobes, is often asymmetric in distribution and often progressive in nature.

Clinical Findings

GBE is more often seen in young men and in cigarette smokers. However, GBE has also been described in non-smokers and patients with alpha-1 anti-protease deficiency. Affected patients may be asymptomatic or experience hypoxia, severe dyspnea, hypoxia, and chest pain.

Imaging Findings

Radiography

  • Bullae occupy more than one third of the affected hemithorax; vary in size, ranging from 1-20cm; average 2-8 cm in diameter
  • Bilateral, although usually asymmetric lung involvement, primarily affects upper lobes
  • Large bullae may compress adjacent lung parenchyma (relaxation atelectasis); invert the ipsilateral diaphragm; contralateral displacement of the mediastinum and anterior/posterior junction lines

MDCT

  • Multiple, large bullae, varying sizes; 1-20cm in diameter; average 2-8cm
  • Bullae predominant in subpleural location; also present in lung parenchyma
  • Usually asymmetric; one lung involved to greater extent than the other
  • Concomitant foci of paraseptal and centrilobular emphysema

Complications

  • Spontaneous pneumothorax
  • “Infected bullae”
    • Common
    • Usually secondary to adjacent lung infection
    • Fluid collection usually sterile; transudative; may persist for weeks-to-months

Treatment

  • Indications for Surgical Intervention
    • Symptomatic patients with significant dyspnea, hypoxia, or complications (e.g., pneumothorax, empyema, or infected bullae)
    • Non-functioning bullae occupying at least one third of the hemithorax compressing adjacent lung parenchyma benefit most from surgical intervention
  • Three main surgical options
    • Video-assisted thoracoscopic surgery (VATS)
      • Minimally invasive
      • Indicated in higher risk patients
      • Bullae are obliterated and the base stapled to prevent air leak
    • Open bullectomy
      • More commonly reserved for patients with large bullae and relatively normal underlying lung parenchyma
      • Bulla is opened, trabeculations lysed; and bulla base is stapled
    • Intracavitary drainage
      • Minimally invasive procedure
      • Overlying rib excised; bulla decompressed using a catheter

Caveats

  • Large bullae may be difficult to differentiate from pneumothorax
  • Presence of visceral pleural reflection denotes pneumothorax
  • Cross table lateral or inspiratory/expiratory studies may help distinguish GBE from pneumothorax

Suggested Readings

  1. Greenberg JA, Singhal S, Kaiser LR. Giant bullous lung disease: evaluation, selection, techniques, and outcomes.  Chest Surg Clin N Am 13 (2003) 631-649.
  2. Parker MS, Rosado de-Christenson ML, Abbott GF. Teaching Atlas of Chest Imaging 2006; Thieme, New York: 296-299.
  3. Stern EJ, Webb WR, Weinacker A, Müller NL. Idiopathic Giant Bullous Emphysema (Vanishing Lung Syndrome): Imaging Findings in Nine Patients. AJR: 162, Feb 1994, 279-282.

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Correct answers by users

Radiology Medicine/Pulmonary
VCU Resident
  • Jonathan Ha
    Others
  • Seth AndersonUnited States of America
  • BOUTHINA IBRAHIMEgypt
  • Ramazan JafariIran
  • PRAGATI KUMARUnited States of America
  • Archana LaroiaUnited States of America
  • Naganathan ManiUnited States of America
  • Wael NemattallaEgypt
  • Giang NguyenVietnam
  • Ravindra PatilIndia
    VCU Department of Thoracic Imaging Virginia Commonwealth University VCU Medical Center