PRE- AND POSTOPERATIVE IMAGING METHODS IN COLORECTAL CANCER

Abstract

Introduction: Among the screening tests for colorectal cancer, colonoscopy is currently considered the most sensitive and specific technique. However, computed tomography colonography (CTC), magnetic resonance imaging (MRI), and transrectal ultrasonography have gained significant ground in the clinical practice of pre-treatment, screening and, more recently, post-treatment and surgical evaluation.

Objective: To demonstrate the high accuracy of CT and MRI for pre and postoperative colorectal cancer staging.

Methods: Search and analysis of articles in Pubmed, Scielo, Capes Periodicals and American College of Radiology with headings "colorectal cancer" and "colonography". Weew selected 30 articles that contained radiological descriptions, management or statistical data related to this type of neoplasia. The criteria for radiological diagnosis were the American College of Radiology.

Results: The great majority of patients with this subgroup of neoplasia is submitted to surgical procedures with the objective of cure or relief, except those with clinical contraindication. CTC colonography is not the most commonly used technique for screening; however, it is widely used for treatment planning, assessment of the abdomen for local complications or presence of metastasis, and post-surgical evaluation. MRI colonography is an alternative diagnostic method to CT, recommended by the American Society of Gastrointestinal Endoscopy. Although there are still no major studies on the use of MRI for screening, the high resolution examination has now shown good results for the American Joint Committee on Cancer TNM classification.

Conclusion: MRI and CT represent the best means for colorectal neoplasm staging. The use of these methods as screening tools becomes beneficial to decrease complications and discomfort related to colonoscopy.

FIGURA 1. TNM system of the American Joint Committee on Cancer (AJCC)

FIGURE 2. T2-weighted coronal (A) and axial (B) sequences demonstrating vegetative lesion on the retosigmoid compromising all layers of its wall (A and B - ❶ and arrow), and with small satellite lymph node (B - ❷ and arrow) . Sagittal T2 - weighted sequences (C) and axial T2FSE (D) characterizing the extension of lesion by infiltration into posterior pararectal fat (C - ❸ and arrows) and anterior pararectal fat bordering the tumor lesion perceived as hypersignal (D - ❺ and arrow ). Parasacral satellite lymph node (C - ❹ and arrow).

FIGURE 3. Sagittal T2 sequences (A), T2 (B) coronal reconstructions, sagittal (C) and axial T2 (D) demonstrating a vegetative lesion that reduces its lumen (A, B and C - ❻ and arrows) compromising all the layers of its wall. Infiltration of the pararectal fat by contiguity (B and C - ❼ and arrows). Deep inguinal lymph nodes involvement (B and D - ❽ and arrows).