IRM du canal anal

The anal canal cancer is a virally induced cancer, mainly of epidermoid type and its incidence is rising. MRI of the anal canal is complementary to endorectal-ultrasonography and clinical examination for the initial evaluation of anal cancer. MRI is performed with T2-weighted and T1-weighted contrast-enhanced sequences into plans related to the orientation of the canal. The initial classification of the lesions is made according to the TNM system: T staging is based on the degree of infiltration of the tumor with an accurate measurement of the tumor and the relationship with the adjacent structures. N staging is based on visualization of peri-rectal, iliac internal, and inguinal lymphadenopathy. The MRI has an initial prognostic interest but is also useful for the follow-up of patients after treatment by radio chemotherapy. The usefulness of the functional sequences (diffusion, perfusion) in the initial evaluation and monitoring is still under assessment. Follow-up examinations to detect a possible recurrence will be carried out according to the same protocol as the initial evaluation. The response to treatment could be complete with a reduction of tumor volume, which last several months after the end of treatment.