Is magnetic resonance imaging useful for the management of patients with rectal villous adenoma? A study of 45 consecutive patients treated by transanal endoscopic microsurgery.

Purpose: Very few data are available about the clinical relevance of magnetic resonance (MR) imaging in preoperative evaluation of rectal villous adenoma. The aim is to evaluate the impact of MR imaging for the surgical management of rectal villous adenoma treated by transanal endoscopic microsurgery (TEM).
Methods: All patients with histologically proven rectal villous tumours operated by TEM who had a preoperative MR imaging between 2009 and 2017 were retrospectively reviewed. All patients underwent TEM because preoperative evaluation suggested systematically usT0 or usT1 tumour. Pathological stage was blindly compared to preoperative MR imaging (location according to the anal verge and the peritoneal reflection, amount of circumferential involvement, tumour size and staging) and preoperative transrectal ultrasonography (TRUS) results.
Results: Forty-five patients were included (24 men, mean age 65 ± 8 years) with TRUS data available only in 37. Pathologic results were pT0-pTis in 32, pT1 in 10 and pT2 in 3. TRUS diagnosed correctly 36/37 lesions (97%) and understaged one pT2 tumour. A significant correlation between TRUS and pathologic results was noted (r = 0.99; p = 0.01). MR imaging diagnosed correctly 19/42 pTis-T1 and 1/3 pT2 tumours (46%). Overstaging by MR imaging was noted in 25 cases (54%). No correlation between MR imaging and pathologic results was noted (r = 0.7; p = 0.3).
Conclusion: Preoperative evaluation of rectal villous adenoma is overstaged by MRI in more than half of the patients. This study suggests that the indication of local excision by TEM for rectal villous adenoma should be based on TRUS rather than on MRI.