Case Author(s): Vreeland, M.D. / Royal M.D. , 11/19/94 . Rating: #D2, #Q5

Diagnosis: Pneumothorax

Brief history:

71 year old man with a right hilar mass presenting with acute onset of shortness of breath. Rule out PE.


Xenon Ventilation Images

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View second image(vq). Perfusion Images

View third image(xr). CXR

Full history/Diagnosis is available below

Diagnosis: Pneumothorax

Full history:

71 year old man with a known right hilar mass presented with acute worsening of shortness of breath. V/Q scan was ordered to rule out pulmonary embolism. CXR was obtained after the scintigraphic evaluation.


Ventilation: Xenon-133 ventilation images shows abnormal ventilation of the left lung, with relative hypoventilation to the left lung base on washin images, and significant retention of activity on washout images. Essentially no activity is appreciated in the right lung on washin images. Faint activity can be appreciated along the right hilum on washout images. Upon careful inspection, a photon defecient area encompassing much of the expected area of the right lung, with overall less activity than the normal background is seen.

Perfusion: Perfusion images demonstrate hypoperfusion to the left lung base in a pattern matching the ventilation abnormality. In addition, perfusion images demonstrate a vertical-band of activity extending along the medial aspect of the right lung on anterior and posterior views. The RPO view demonstrates the anterior-posterior extent of perfusion within the right lung. No focal, large, segmental, wedge-shaped perfusion defects are noted in the left middle and upper lung fields. Overall, perfusion is slightly better to the right lung lung, when compared with the same area on the ventilation images.

CXR: Standard chest radiograph obtained after worrysome findings on the ventilation/perfusion scans demonstrate a large, secondary pneumothorax, with marked collapse of the entire right lung.


Unilateral, matching lung defects are unlikely to represent pulmonary emboli, especially if the other lung is normal or only has small, peripheral, perfusion defects. Likewise, matching unilateral lung defects are more likely to be caused by other etiologies.

Secondary pnuemothorax may occur iatrogenically with procedures or may be secondarily associated with lung or pleural-based masses, especially in individuals with underlying cardiopulmonary diseases, such as asthma, COPD, etc.

When evaluating a ventilation/perfusion scan for pulmonary embolism, one should have a recent, standard chest radiograph. The chest radiograph should be within 24 hours of the acute event and prior to performing the V/Q scan. A significant change in the respiratory status or acute symptoms would dictate obtaining a more recent chest radiograph, even if a chest radiograph had already been obtained within 24 hours. A recent chest radiograph is required to interpret the V/Q scan; however, more importantly, it may identify other etiologies responsible for the patient's symptoms, such as pnuemothorax.


A chest tube was successfully placed; the patient's symptoms improved placement of the chest tybe; and, subsequent radiographs showed reexpansion of the right lung.

Differential Diagnosis List

The most common cause of unilateral lung perfusion defects result from bronchogenic carcinoma or a space-occupying lesion. Other less common etiologies include pnuemonectomy, large pleural effusion, mucous plugging, endobronchial lesion (iatrogenic), and mediastinal or hilar masses, such as sarcoidosis, fibrosising mediastinitis, or lymphoma, etc. uncmommon causes of this finding would include pulmonary embolisim, Swyer-James Syndrome, foreign body, injection into a pulmonary catheter, and pulmonary vein or arterial hypoplasia.

ACR Codes and Keywords:

References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Organ specific)

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Case number: vq005

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