Pop Quiz – Final Answer!

So what was wrong with that post-chest tube x-ray taken after placement for treatment of a pneumothorax?

The answer? The chest tube is not in the chest!

But wait, you say. That x-ray looks totally normal. The placement couldn’t be more perfect!

Remember, an x-ray image is a 2D representation of a 3D object. You can easily see the location of the tube in the x and y axes, and it looks great. But the z (depth) axis? You have no clue. And in this case, the tube is along the posterior chest, under the scapula. That’s a potential reason for the persistent pneumothorax.

Some readers commented that the tube could be in the lung parenchyma or a fissure. Fissure placement does occur occasionally, and may hamper the function of the tube somewhat, but it will still work. My radiology colleagues occasionally call me to warn that the tube goes through the lung parenchyma. Fortunately for the patients, this is almost never true. Just an illusion seen on the CT. It is very difficult to place a tube through normal lung. The resistance is substantial enough to make any reasonable person stop pushing. Hopefully.

Bottom line: Remember that a plain x-ray is only two dimensional. Your brain will place the objects seen on it wherever you desire. But you do not know how deep or superficial any object is without additional information. Even CT scans simulate 3D by stacking a bunch of this slices or shaded images to fool your brain. When placing a chest tube, verify its insertion point with your finger; you can follow the tube down to the chest wall and feel it vanish between the ribs. Don’t just assume you know where it’s going.

Hat tips to @CookCountyTraum, HollyT and Josh for getting it correct!

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