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

Abstract

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.

Endoscopic ultrasonography and computed tomography scanning for preoperative staging of colonic cancer

“…Nonetheless, EUS is still used in rectal cancer, especially for early tumours [20]. In general, EUS allows multimodal examinations that could be useful for evaluation of rectal cancers, clearly distinguishing the layers of the rectal wall (EUS), measuring tumour volume (3D ultrasound) and characterizing tumour microvasculature (EUS with contrast enhancement) [21]. EUS with contrast enhancement for quantification of perfusion after chemotherapy has been suggested to predict treatment response within 3 days and before morphologic changes usually occur in solid tumours [22,23].…”

Endoscopic Ultrasound Elastography in the Assessment of Rectal Tumors: How Well Does It Work in Clinical Practice?

“…Other nodes involved are considered metastases [ 15 ]. Although the characterization of pathological lymph nodes does not include their elasticity, in practice, during elastography, they appear stiffer than the perirectal fat [ 16 ].…”

Endoluminal Ultrasonography of the Rectum and the Anal Canal

“…The T re-stage accuracy is 50% (Figure 13) [35][36][37][38]. The accuracy can be improved by depicting the intense and chaotic vasculature of residual tumor tissue through Doppler technique [39] or contrast-enhance ultrasound [40,41]. Endoscopic ultrasonography of rectum can also be used for rectal cancer recurrence postoperatively with high accuracy [41,42].…”

“…Obtaining biopsy samples through fine needle aspiration improves the detection of rectal recurrences. Also depiction of the vascularization through Doppler techniques or CEUS can considerably increase the specificity of transrectal ultrasound in differentiating tumor relapse from fibrosis [39,40,43]. The endoscopic ultrasound is recommended for follow up after surgery at six months interval for two years [24].…”