The Diagnostic Workup for Colon and Rectum Cancer: Tests, Scans and Staging

Yes. Rectal cancer spreads upward along its natural embryological lymphatic supply rather than downward, so staying strictly within that anatomical plane allows the tumour to be removed completely, following guidelines that show even a minimal distal margin of one centimetre is adequate. An intraoperative frozen section can confirm all microscopic cancer cells have been cleared, and this makes it possible to go between the internal and external anal sphincter even for the lowest-lying tumours, preserving a normal passage instead of requiring a permanent stoma.

Follow the natural avascular surgical plane, doing sharp dissection between the internal and external sphincter. On gross examination, aim for about one centimetre of margin at the lowest extent of the tumour, or three to five centimetres higher up depending on where the tumour is located. Stay within the correct surgical plane and the margin should come back clear; the final histopathology report, once it arrives, confirms this.

Do whatever is genuinely achievable under your own control. If something cannot be done locally, it is better to refer the patient to a centre where it can be done with precision, because cancer gives only one real chance to get the treatment pathway right.

It is called complete mesocolic excision with central vascular ligation, sometimes shortened to CME with CVL. The feeding blood vessels of the tumour are ligated right at their origin so that all the draining lymph nodes and the complete mesocolic fascia are removed together; this has been published in international journals and is associated with better survival than the standard technique.

If the liver metastases are limited, roughly one to three, and can be completely removed, liver metastasectomy can be done at the time of the primary surgery or as a second stage. If the liver is diffusely involved in both lobes, there is no role for curative surgery and only palliative chemotherapy is appropriate. If instead there is peritoneal-only spread with no other site involved, cytoreductive surgery combined with HIPEC gives a survival advantage of about fifty percent in colorectal cancer, provided the disease is limited and combined with chemotherapy before and after.

Colonoscopy with biopsy, an MRI of the pelvis, a CT scan of the thorax and abdomen, a tumour marker blood test, and a PET-CT scan where available.

It is most valuable for tumours lying very low in the rectum, to check whether the pelvic floor muscles are involved and whether a stoma will be needed.

Yes. A fecal occult blood test can be done even at a primary or general hospital; it is not highly specific but still helps flag patients for further evaluation.