Lung Ultrasound: Aurora Sign and Parenchymal Lung Disease

Multiple ring-down artefacts (RA) can be seen on the dorsal side of right hepatic lobe on abdominal ultrasound examination. These artefacts are normally noted in the subcostal or intercostal views. When these ring-down artefacts are numerous, they are termed as aurora sign or retrohepatic diffuse hyperechogenicity.

The high echo bands that occur in the dorsal side of the right hepatic lobe 3 to 10 mm wide and 30mm or greater in length were defined as ring-down artefacts. To qualify for the term aurora sign the number of ring-down artefacts has been arbitrarily set at more than 20. Aurora sign indicates pulmonary parenchymal pathology in the right lower lobe of lung. The commonest pulmonary pathology associated with aurora sign is interstitial lung disease. When aurora sign is noted in otherwise normal patient in abdominal examination, detailed respiratory history with chest X ray and referral to pulmonary specialist may be considered.

Rarely aurora sign can occur in the absence of obvious pulmonary pathology, the significance of which is unclear at present. In individual with positive aurora sign and negative HRCT scans, the possibility of interstitial inflammation not obvious on the HRCT may be considered.

The name ‘aurora’ comes from the natural light display in the sky in high latitude regions like Arctic and Antarctic. See wiki for more info.