Objective Although prior studies have evaluated complications following endoscopic ultrasound (EUS), data on the incidence of unplanned events at EUS, defined as any deviation from the preprocedure plan, are lacking. The aim of this study was to define the incidence, nature, clinical predictors and implications of unplanned events at EUS.

Design Case control study.

Setting Tertiary referral centre.

Patients 4624 consecutive patients undergoing EUS during a 6 year period were enrolled. For each patient with an unplanned event, two patients with a successful EUS in the same calendar year were randomly selected as controls.

Main outcome measurements Unplanned events occurring prior to, during or after EUS procedures were prospectively recorded in a database.

Results 192/4624 patients had an unplanned event (4.1%). In all, 2.1% had a failed procedure for anatomical reasons, 1.3% because of restlessness despite standard sedation and 0.5% for technical reasons. Adverse events occurred in 0.2%. There was no mortality but 4/6 patients with adverse events had to be admitted to hospital (2/4 operated). Eighty-two per cent of patients with an unplanned event had incomplete examinations, 14% had no procedure performed and 4% had complete procedures. In a multivariate analysis, only Afro-Caribbean patient origin, inpatient procedure and cancer staging procedure were independently related to unplanned events (p<0.05 for all).

Conclusions Unplanned events at EUS are mainly due to anatomical reasons and restlessness, despite sedation. They commonly result in incomplete examination and are related to Afro-Caribbean origin, inpatient procedure and cancer staging.