Thoracic Ultrasound Demonstrates Variable Location of the Intercostal Artery

<i>Background:</i> Ultrasound (US) guidance is advocated to reduce complications from thoracocentesis or intercostal catheter (ICC) insertion. Although imaging of the intercostal artery (ICA) with Doppler US has been reported, current thoracic guidelines do not advocate this, and bleeding from a lacerated ICA continues to be a rare but serious complication of thoracocentesis or ICC insertion. <i>Objectives:</i> It was the aim of this study to describe a method to visualise the ICA at routine US-guided thoracocentesis and map its course across the posterior chest wall. <i>Method:</i> The ICA was imaged in 22 patients undergoing US-guided thoracocentesis, at 4 positions across the back to the axilla. Its location, relative to the overlying rib, was calculated as the fraction of the intercostal space (ICS) below the inferior border of that rib. <i>Results:</i> An ICA was identified in 74 of 88 positions examined. The ICA migrated from a central ‘vulnerable’ location within the ICS near the spine (0.28, range 0.21–0.38; p < 0.001) towards the overlying rib (0.08, range 0.05–0.11; p < 0.001) in the axilla. <i>Conclusions:</i> The ICA can be visualised with US and is more exposed centrally within the ICS in more posterior positions; however, there is a marked variation between individuals, such that the ICA may lie exposed in the ICS even as far lateral as the axilla. Future studies need to identify which patients are at risk for a ‘low-lying’ ICA to further define the role of US imaging of the ICA during thoracocentesis or ICC insertion.