Inferior pulmonary ligament

Last revised by Liz Silverstone on 16 Dec 2024

The inferior pulmonary ligament (or pulmonary ligament) is not a true ligament; it is a normal and variable pleural fold which is sometimes seen on CT and may cause a triangular peak along the diaphragm on CXR.

The inferior pulmonary ligament is formed by a double layer of visceral pleura with mediastinal pleura and connective tissue that extends from the root of the hilum towards the dome of the hemidiaphragm. It tethers the medial surface of the lower lobe to the mediastinum and allows hilar vessels to dilate when cardiac output is increased.

  • thin, linear structure that inferior to the hilum on lung windows 3

  • most apparent at the level of the hemidiaphragm arising from the paraesophageal mediastinum 4

  • twice as commonly seen on the left than the right; evident in ~50% of patients 2, 3

Cases and figures

  • Figure 1: right lung
  • Case 1: left-sided
  • Figure 2: left lung
  • Case 2: left lower lobe collapse

Imaging differential diagnosis

  • Inferior pulmonary fissure (right)
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