4.2 Study limitations
A mean follow up time of 6 years (median 5.6 years) is not long enough to allow for the development of all potential recurrences, therefore we expect that the recurrence rate may increase with time. The focus of this study was to detect occult recurrences at an early stage with imaging rather than define the incidence of RPA after CD which has already been discussed in the literature2,6. Another limitation is that a small recurrence may not be obvious on MRI or CT and therefore repeat imaging may be necessary. Lesions as small as 1 mm have been detected with MRI5. However, histopathological studies show that recurrences can be multiple and less than 1mm9 so there is a theoretical risk of missing them by imaging. CT scans have inferior detection capability compared to MRI but only few patients underwent this modality in our study.