Invisible Active Bleeding Due to the Watershed Phenomenon.

A case is presented of an 83-year-old female patient with a strong suspicion of active bleeding, but no diagnostic contrast blush could be seen on the original computed tomography (CT) scan. Teaching point: When performing CT angiography in veno-arterial extracorporeal membrane oxygenation (VA-ECMO), it is important to understand the altered haemodynamics, as flow-related artefacts such as the vascular watershed phenomenon can obscure bleeding.