J Korean Med Assoc.  2009 May;52(5):509-517. 10.5124/jkma.2009.52.5.509.

Preoperative Radiological Staging of Rectal Cancer

• Kim MJ

• KMID: 2188018
• DOI: http://doi.org/10.5124/jkma.2009.52.5.509

Abstract

Rectal cancer is a common malignant disease that continues to have a highly variable outcome, with local recurrence after surgical resection usually leading to an incurable disease. Local recurrence is dependent upon tumor stages and surgical techniques. There is no general consensus on the role of transrectal ultrasonography (TRUS), computed tomography (CT), and magnetic resonance imaging (MRI) in staging of rectal cancer. The role of preoperative imaging is to determine which therapy may be suitable for the patients by surgery alone or with additional treatment. Although the tumor stage is an important prognostic factor, the evaluation of the involvement of the mesorectal fat and mesorectal fascia is even more important. New developments in techniques such as coils, sequences, and gradients in MRI, and evolution of multidetector CT (MDCT) allow better diagnostic options for patients with rectal cancer. Highresolution MRI has proved useful in clarifying the relationship between the tumor and the mesorectal fascia, representing circumferential resection margin at total mesorectal excision. At present, MRI is superior to CT or TRUS for assessing the local staging of rectal cancers. However, nodal staging remains a difficult radiological diagnosis. The role of MDCT has to be set, but for distant metastatic disease it remains to be the first option. This review discusses on the current role of the various imaging modalities in preoperative staging of the rectal cancer.

Keyword

Rectum; Neoplasm; Ultrasound; CT; MRI

MeSH Terms

Consensus
Fascia
Humans
Magnetic Resonance Imaging
Rectal Neoplasms
Rectum
Recurrence

Figure

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  Figure 1 Diagram of the mesorectum shows the relationship of the rectum to fascial planes in axial (A) and coronal (B) planes. Adopted from (6).

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  Figure 2 Transrectal ultrasonograhy image at mid-rectal level shows five sonographic layers; the mucosa and submucosa (white arrowhead) are echogenic, the inner hypoechoic layer corresponds to the muscularis mucosa (white arrow), and the outer hypoechoic layer corresponds to the muscularis propria (black arrow).

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  Figure 3 Transrectal ultrasonography images of rectal tumor. (A) T1 tumor does not reach the muscularis propria (black arrows) but is confined by a echogenic layer of submucosa (white arrows). (B) T2 tumor shows that the muscularis propria has been invaded by tumor (black arrows) but that is no extension beyond the wall (white arrows). (C) T3 tumor (black arrows) extends through the muscularis propria (white arrows) into the echogenic mesorectal fat.

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  Figure 4 Diagram shows the relationship between the CRM and rectal tumors of various stages. Adopted from (7). The most powerful predictor for local recurrence is the shortest distance from tumor to mesorectal fascia (ie, the CRM) (double-headed arrows). The actual T staging system does not differentiate between tumors with a wide CRM (t3Δ) and those with a narrow CRM (T3*). T3* poses a higher risk for recurrence. It would be more important to be able to identify on images those bulky tumors that will have a close or involved resection margin than to predict the exact T state of the tumor. T1 = T1- stage tumor, T2 = T2-stage tumor, T4 = T4-stage tumor, Ves Sem. = vesicular seminalis.

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  Figure 5 Normal rectal MRI anatomy. The oblique axial (A), oblique coronal (B), and sagittal (C) T2-weighted turbo spin-echo MR images show the muscularis propria as the outermost hypointense rectal layer (black arrow), the intact mesorectal fat (asterisks) and the normal appearance of the mesorectal fascia (white arrows).

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  Figure 6 Variable T staging of rectal cancer at MRI. (A) Axial turbo spin-echo T2-weighted MR image shows a polypoid mass (*) involving the mucosal, submucosal, and muscular layers presenting T2 rectal cancer. The muscularis layer is visible as a hypointense line, and no spread into the mesorectal fat (arrow). (B) Axial T2-weighted MR image shows T3 rectal cancer (black arrow) disrupting the muscular layer and invading surrounding mesorectal fat which does not involve the mesorectal fascia (white arrows). (C) Sagittal T2-weighted MR image shows a T4 rectal cancer (arrows) disrupting the mesorectal fascia and infiltrating the prostate (*). (D) Axial T2-weighted MR image shows the enlarged lymph node (arrow) within the mesorectal fat, that was confirmed as malignant lymph node.

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