Skinfold artifact

Last revised by Liz Silverstone on 24 Sep 2024

The skinfold artifact can be mistaken for a pneumothorax on chest radiography and is caused by the added density of a skin fold against the image. It appears as a broad opacity indistinct medially and sharply outlined laterally (Mach band effect) 2,3.

Radiographic features

Plain radiograph

The following features may help differentiate a skin fold from a pneumothorax:

  • normal pleura is less than 1 mm thick

  • visceral pleural is seen as a thin line well-defined on both sides in contrast to the broad opacity of a skinfold which is well-defined laterally and ill-defined medially

  • a skinfold does not follow the expected course of the pleura

  • a skinfold often extends outside the hemithorax, pleura never does

  • peripheral hypertransradiancy is present in pneumothorax

  • pneumothorax results in absent bronchovascular markings beyond the lung edge (occasionally markings are visible if pneumothorax is loculated)

  • skin folds are frequently seen on portable chest radiographs - patients slide downwards after the cassette has been positioned

Differential diagnosis

The soft tissues of the medial arm can project over the lateral chest and mimic a pneumothorax and skin fold.

Cases and figures

  • Case 1: right lower zone
  • Case 2
  • Case 3

Imaging differential diagnosis

  • Medial arm mimicking pneumothorax
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