Overcrowding in the emergency department (ED) has been a global problem for a long time, but it is still not resolved.

To determine if an ED expansion would be effective in resolving overcrowding.

This was a retrospective study comparing two 10-month periods before (September 2015 to June 2016) and after (September 2017 to June 2018) the ED expansion in an urban tertiary hospital. The existing ED consisted of 45 beds in the adult area and eight beds in the pediatric area. After the construction, the number of beds was not increased, but a fast track area was newly established in the adult area, and a 25-bed ward for emergency hospitalized patients was opened.

The number of patients visiting the ED increased from 77,078 to 87,927. The proportion of patients who returned home without treatment significantly decreased from 11.5% to 0.9% (p<0.001). The number of adult patients increased from 40,814 to 60,720, but the number of patients who could be treated on the bed decreased (22,166 (54.3%) vs. 17,776 (29.3%), p<0.001). The number of pediatric patients was similar in both periods. Median ED length of stay (LOS) of total patients increased from 193.0 min to 205.8 min (p<0.001). Of the 18,900 hospitalized patients during post-period, 1,255 (6.64%) were admitted to the emergency ward, and the boarding (from admission decision to hospitalization) time of the admitted patients decreased from 239.2 min in the pre-period to 190.9 min in the post-period by 38.3 min. However, more time was required for admission decision in the post-period (216.8 vs. 253.3, p<0.001).

The ED expansion allowed more patients to be treated, and the emergency ward reduced boarding times of admitted patients. However, due to the increase in the number of patients, the time required for medical treatment increased.