Characterization and staging of rectal tumors: endoscopic ultrasound versus MRI / CT. Pictorial essay.

Endoscopic ultrasound is recommended for rectal cancer staging. Transrectal ultrasound approach is able to overcome one of the limitations of this technique regarding circumferential rectal stenosis. Prior intrarectal administration of a small amount of fluid contrast agent optimizes the method, making it easier to distinguish the layers of the rectal wall and tumor formation. Endoscopic ultrasound focuses on the gray-scale mode. Additional procedures provide useful information for tumor assessment: Doppler ultrasound helps identify chaotic intratumoral vascularization; 3D ultrasound allows the assessment and accurate measurement of the tumor; elastography can identify focal tumor dysplasia within adenomas; contrast-enhanced ultrasound allows characterization of tumor microvasculature. Even if they are not as accurate in distinguishing rectal wall layers, cross-sectional imaging techniques (CT, MRI) can identify the anatomical relationships of advanced locoregional cancers, as well as possible distant metastasis. This paper aims at illustrating the main pathological aspects of endoscopic ultrasound multimodal examination useful for cancer staging.