CASE 7

A 51-year-old female presented with rectal bleeding and weight loss for 4 months. On Digital Rectal Examination (DRE) the ulcerated inferior edge of the disease is felt at the approximately 5-6 cm from anal verge, anal canal is spared. Colonoscopy revealed a 4 cm fungating, ulcerated mass in the middle &  low rectum, which was diagnosed as moderately differentiated adenocarcinoma. Staging workup classified the tumor as cT2N1M0. CT of the chest and abdomen showed no evidence of distant metastasis. Following a multidisciplinary discussion, the patient was planned for total neoadjuvant therapy (TNT), consisting of chemoradiotherapy with Xeloda followed by FOLFOX chemotherapy.

IMAGING FINDINGS

CT Scan: 

Diffuse concentric thickening of the rectal wall at the middle rectum, approximately 7 cm from the anal verge, with a semicircumferential pattern, lobulated contours. An enlarged left external iliac lymph node is also noted, but there is no distant metastasis.

MRI: 

Diffuse concentric thickening of the rectal wall at the middle rectum, 7 cm from the anal verge, with a semicircumferential pattern, lobulated edges. The lesion is hypointense on T1, T2, and STIR sequences, showing intense and homogeneous post-contrast enhancement. There is no disruption of the muscular layer, and a clear interface with the mesorectum and anterior peritoneal reflection is maintained. Additionally, left external iliac adenopathy is visualized.

IMAGING

T2 Axial View

T1c Sagittal View

T2 Axial View

Learning Points

MRI Pelvis in Ca Rectum

• MRI is the modality of choice when it comes to staging rectal cancer, located up to approximately 15 cm from the anal verge

• facilitates the accurate assessment of mesorectal fascia and the sphincter complex for surgical planning

• Response assessment to treatment Intervention.

• Tumor Staging: Assess depth of invasion (T1-T4) and relation to the mesorectal fascia (MRF).

• CRM Assessment: Evaluate proximity to circumferential resection margin.

• Lymph Nodes: Identify the size, shape, and characteristics of mesorectal and pelvic nodes.

• EMVI: Look for extramural venous invasion (spiculated vascular structures).

• Sphincter Involvement: Assess for internal/external anal sphincter invasion.

• Adjacent Organs: Check for bladder, prostate, or uterine involvement.

• Peritoneal Reflection: Determine if the tumor extends above or below it.

• Response to Therapy: Evaluate tumor regression post-neoadjuvant treatment.

• Techniques: High-resolution T2-weighted images, DWI for activity, contrast for recurrence.

• DRE is an essential component in the management of Ca Rectum

• Correlate DRE findings with imaging for correct Target volume delineation for radiation therapy

• Also essential to perform DRE during chemotherapy to asses response to treatment