Synopsis

Keywords: Body: Digestive

In current clinical practice, MR imaging plays a limited role in the study of small and large bowel tumors, if we exclude rectal cancer. In fact, most patients with either a suspected small bowel neoplasm or with a need of colon cancer staging is referred to a MDCT evaluation. However, high soft tissue contrast, multiplanar imaging acquisition, as well as the possibility of performing functional studies make MR a promising technique to study these diseases. The possibility of using MRI in assessing small and large bowel tumors depends on the unmet clinical needs which cannot be fully satisfied by MDCT.

In current clinical practice, MR imaging plays a limited role in the study of small and large bowel tumors, if we exclude rectal cancer. In fact, now most patients with either a suspected small bowel neoplasm or with a need of colon cancer staging is referred to a MDCT evaluation. Reasons are variable: CT availability; exam robustness (especially in elderly and fragile patients); patient clinical presentation (in the case of bowel obstruction CT is performed in an emergency setting).However, high soft tissue contrast, multiplanar imaging acquisition, multiparametric analysis, including “functional” studies (i.e., diffusion and perfusion) make MR a promising technique to study these diseases.Small and large bowel tumors are two very different entities: rare, heterogenous in histology (the most common tumors are adenocarcinoma, neuroendocrine neoplasms, gastrointestinal stromal tumors, and lymphoma), growth pattern and aggressiveness the small bowel tumors; very common and homogeneous in histology the colon cancers.The future success of a routinary use of MRI in assessing small and large bowel tumors depends on the unmet clinical needs which cannot be fully satisfied by a MDCT study.In the case of small bowel tumors, advantages of using MRI are the more accurate assessment of liver metastatic disease, especially in NET, the evaluation of distant spread outside liver, especially if a whole-body MR approach is used, the precise characterization of a primary lesion, based on a multiparametric analysis. In the case of colon cancer, there is a clear demand of a more accurate local staging, especially in locally advanced disease. This is due to the widespread use of neoadjuvant chemotherapy in colon cancer which improves patient outcome. Thus, local staging of colon cancer needs a detailed study of several factors affecting patient outcome, similarly to rectal cancer: extra-mural spread, extramural vascular invasion (EMVI), tumor deposits and lymphnodes. Although a limited number of studies is available, it can be argued that MR may be beneficial compared with CT in differentiating locally aggressive (T3cd/T4) vs less aggressive (T2/T3ab) tumors; in assessing venous invasion and in characterizing tumor deposits and lymphnodes.

Acknowledgements

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