Rectal cancer staging.

Endorectal-US is the most suitable imaging technique in the initial staging of rectal cancer and it is mostly accurate in evaluating early stages and in demonstrating the perirectal spread of cancer tissue. CT is not able to demonstrate the layers of the rectal wall and its accuracy in demonstrating the invasion of muscolaris propria and perirectal fat is lower than other techniques, so its use in local staging is not recommended. MRI is mostly accurate in evaluating the mesorectum and the mesorectal fascia which are considered the most relevant prognostic factors for local recurrence. Lymph node evaluation is a challenge for every imaging techniques since lymph node size is not a reliable criterion for diagnosing metastatic involvement. Nuclear medicine has a remarkable role in the work-up of rectal cancer and in the next future the combination of FDG PET in conjunction with a dedicated contrast enhanced CT protocols could become a single-step staging procedure.