What should we do about crowding in emergency departments?

Our emergency departments have never been under so much pressure. Crowding in these departments is both a cause and symptom of this pressure. Crowding kills patients and harms staff. It is the most important problem affecting emergency departments in the UK. The causes are described and include factors relating to input, throughput and output. Interventions aimed at these causes may confer benefit, but the most important problem remains unsolved. This is exit block caused by lack of beds, and flow through those beds, exacerbated by downgrading of capacity in unscheduled care in the evenings, weekends and during holiday periods.