Incidental Findings and Their Significance in Rectal MRI: UK Experience

Rectal MRI studies used to stage and guide surgical or nonsurgical management of rectal cancer may harbor incidental findings (IFs) of varying significance. St George's Hospital uses a four-sequence MRI protocol which does not employ diffusion-weighted imaging (DW-MRI).

To determine the frequency and significance of incidental findings identified when using a rectal MRI protocol which does not employ DW-MRI.

Retrospective analysis of rectal MRI study reports for IFs and stratifying their significance. Medical records were reviewed to clarify IFs of interest.

One hundred thirty-four studies met the inclusion criteria for the study (75 men, mean age 65). 51/134 (38%) of studies had IFs. Fifteen percent (n = 7/46) of baseline studies for a new cancer had significant IFs. The commonest IF was diverticular disease (n = 10); however, a bladder malignancy was also identified.

Clinically significant IFs exist in 12% of patients undergoing rectal MRI, and any type of IFs exist in 38% of patients undergoing rectal MRI studies. The rate of significant IFs is comparable with other authors both in rectal and prostate MRI but with fewer overall IFs, possibly due to the lack of DW-MRI sequences in our local protocol. Our study is the first to assess IFs using a rectal MRI protocol which does not employ DW-MRI, and the results should be considered by centers when planning their rectal MRI protocol.