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Challenge of the Unknowns—Unknown 6

Diagnosis and Discussion

DIAGNOSIS: Spontaneous pneumothorax.


The key to the diagnosis of pneumothorax is the absence of all lung markings in the superolateral portion of the left hemithorax. This represents the air which is between the visceral and parietal layers of the pleura -- a space which is normally only a potential space. The "mass", of course, represents the collapsed left lung (primarily the upper lobe portion in this case). The crisp peripheral margin of the collapsed lung is not usually found in neoplasm, another clue that this is not a tumor.

Spontaneous pneumothorax can occur without pre-existing lung conditions (primary) or secondarily to a chronic or acute lung problem. Primary spontaneous pneumothorax is particularly common in tall people as a result of a small, occult bleb within the apical pleura. Secondary spontaneous pneumothorax is common in asthmatics. The underlying cause is over-expansion of peripheral alveoli which burst. This allows air that is breathed in to escape to the pleural space. With each breath the patient takes, more air is added to the pleural space and less lung expansion takes place until the lung is fully collapsed.

Other risk factors for secondary spontaneous pneumothorax include: other obstructive airway diseases such as emphysema; neoplasms, especially chest wall neoplasms such as mesothelioma; connective tissue disorders like Marfan's disease; cystic lung disease such as cystic fibrosis; and, infections.

A complication of either primary or secondary spontaneous pneumothorax is "tension". This occurs when a stop-valve mechanism is created at the tear within the visceral pleura. Air volume and pressure outside the lung build to dangerous levels. This can be fatal due to pressure exerted on the heart and great vessels.

The treatment for tension pneumothorax involves siphoning off the extrapulmonary air. A first time occurrence of pneumothorax is usually treated conservatively by allowing the lung reinflate passively over a period of a few days all while watching for signs of tension. Serial radiographs follow the progress of this treatment. Recurrence is common, however. With recurrent spontaneous pneumothorax the visceral pleural is permanently fused to the chest cavity in a procedure called pleurodesis.

Case courtesy of Dr. Jason Bartlett, DC, of Woodbury, Minnesota


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