Learning Radiology xray montage

Subsegmental Atelectasis (SSA)
Discoid Atelectasis, Platelike Atelectasis


General Considerations

  • Seen especially in post-operative patients, usually at the lung bases
  • Can also be seen with pulmonary thromboembolic disease, obesity, ascites
  • Believed to be caused by a decreased production or inactivation of surfactant which, when present normally, keeps the alveoli from collapsing by decreasing the surface tension
  • Not caused by obstruction of bronchi

Clinical Findings

  • Most patients have some form of splinting which prevents a full inspiration
  • SSA is usually asymptomatic by itself; it is the result rather than the cause of limited inspiration

Imaging Findings

  • Thin, linear opacities at one or both bases, 2-10 cm in length, usually horizontally oriented
  • Crosses segmental boundaries
  • May rarely occur in upper lobes and may be vertically oriented
  • No associated signs of volume loss (no shift of fissures)
  • Clears in a few days or less

Differential Diagnosis

  • Linear scarring  - may look the same on one radiograph; SSA will almost always clear in a few days; scarring will not


  • Incentive spirometry
  • Chest physiotherapy  

 discoid, subsegmental, platelike, atelectasis

Subsegmental Atelectasis, Left Lung Base. There are multiple, thin, linear opacities (red arrows) at the left base oriented horizontally. The patient is post-operative colon surgery.