Objective: The identification and management of incidental findings is becoming increasingly problematic, particularly in relation to brachial plexus imaging because the prevalence is unknown. Therefore, we aimed to estimate the prevalence of incidental findings in symptomatic patients undergoing MRI of the brachial plexus.
Methods: This retrospective cohort study included all children and adults who underwent MRI over a 12-year period, in a tertiary care centre in the UK. An incidental finding was any abnormality which was not a direct injury to or disease-process of the brachial plexus. An "incidentaloma" was defined by the need for further investigation or treatment. Multivariable logistic regression was used to estimate the odds ratio (OR) of an "incidentaloma". To estimate which factors were associated with the incident rate ratio (IRR) of incidental findings, multivariable Poisson regression was used.
Results: Overall, 502 scans (72%) reported incidental anomalies. Although the number of MRIs performed per annum increased by 23%, the prevalence of "incidentalomas" remained static (p = 0.766). Musculoskeletal incidental findings were the most prevalent (63%) and when identified, there were a median of 3 incidental anomalies per patient. Overall, 125 (18%) anomalies were "incidentalomas" which required further investigation or treatment. The odds of having further investigation or treatment was strongly related to the frequency of incidental findings [adjusted OR 1.16 (95% CI 1.08, 1.24)] and when a tumour was identified [adjusted OR 2.86 (95% CI 1.81, 4.53)]. The number of incidental findings recorded per scan increased when trainees co-reported with consultants [adjusted IRR 0.36 (95% CI 0.05, 0.67)] and in the presence of a tumour [adjusted IRR 0.39 (95% CI 0.28, 0.49)].
Conclusions: The prevalence of clinically important incidental findings on brachial plexus MRI is lower than organ-specific imaging, but still 18% of scans identified an 'incidentaloma' which required further investigation or treatment.
Advances in knowledge: This cohort study shows that approximately 1 in 5 symptomatic patients undergoing a brachial plexus MRI had a clinically important incidental findings, which required further investigation or treatment. This information can be used to inform patients consenting to clinical or research imaging.