Answer to Medical Challenge | X-Ray Interpretation

Posted on July 16, 2011

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**If you would like another chance to read the challenge before seeing the answer, click here.  Scroll down for the answer.  **

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Thanks for your savvy observations & guesses.  This was a difficult/tricky question – I kept my medical friends in the dark by leaving out information like vitals and the physical exam, because radiologists often read images without much else to go on.  Additionally, the brief history I provided was intentionally misleading, and the image quality is poor.

The correct answer is D) Left pneumonectomy.  The trachea & bronchi are deviated to the left, as are cardiac silhouette and mediastinal elements, suggesting volume loss on that side.  Congratulations, if you chose D, you prevented your patient from receiving an unnecessary chest tube (ouch!).  Other clues that would lead you to suspect a pneumonectomy are the presence of a resected rib (usually 5th) and absent breath sounds or dullness (not hyperresonance) to percussion on the affected side, along with a history consistent with such a procedure (e.g. lung cancer).

What’s funny is that my mother, with no medical training (which in this case may have served to mislead you), glanced at the image and remarked “looks like he’s missing a lung.”  Go figure.

Explanation (+ clinical pearls):

Total opacification of a lung field or hemithorax should prompt a differential that includes the following:

  • Atelectasis (collapsed lung)
  • Pleural effusion (fluid in the membranes of the thorax, compressing the lung)
  • Pneumonia
  • Hemothorax (blood in the chest)
  • Pneumonectomy (removal of lung tissue)

It would certainly help to have a physical exam and a good history for this patient, but you can make the call with confidence by the x-ray alone in this case.  In general, when there is volume loss (atelectasis, pneumonectomy) there is a shift of the trachea towards the side that has lost volume.  When there is a mass (cancer) or presence of blood or fluid on one side of the chest, there is a shift of the trachea and mediastinum (heart, etc.) away from the lesion.

Left hemothorax is incorrect, as the trachea and heart would be expected to be shifted to the right in the absence of other pathology.  Additionally, on exam the patient may be noted to have flat neck veins, a rapid heart rate, and dullness to percussion on the left side.

Right pneumothorax is incorrect because there are visible lung markings at the periphery.  Physical findings consistent with pneumothorax would include respiratory distress, distended neck veins (impaired venous return), absent breath sounds, and hyperresonance to percussion on the right, and the “deep sulcus sign” on the radiograph.

Ruptured left diaphragm is incorrect because while the left hemidiaphragm is obscured, one would expect the stomach and/or bowel to herniate into the chest, shifting the aforementioned structures to the right.  Additionally, bowel with air-fluid levels may be noted on the x-ray, and bowel sounds may be heard over the left lung field along with dullness to percussion.  Diaphragmatic rupture (as in blunt trauma) is more common on the left, presumably due to protection afforded by the liver on the right.

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Posted in: Medicine