Colon:
The lymphatics from the
subserosal and submucosal plexus drains first to the epicolic nodes
next to the bowel wall and thence to the paracolic nodes along the
marginal artery or its branches and then to the intermediate nodes
along the main vessels or its branches and thence to the principal
nodes along the root of the SMA or IMA in front of the aorta.
Rectum:
The anal canal above the
dentate line and the rectum drain upwards along the perirectal nodes in
the mesorectum and thence to the intermediate nodes at the bifurcation
of the Superior rectal artery and thence to the principal nodes along
the IMA and Paraaortic nodes. Retrograde spread of malignancy can occur when
the principal nodes are blocked by tumour, in which case one can expect tumour
to spread to the external iliac and inguinal regions.
Anal canal:
Anal canal below the dentate line drains into the perianal lymphatic plexus and thence to the inguinal nodes.