However, distal rectal cancers may metastasize initially to the lungs through the inferior rectal vein
, which drains into the inferior vena cava rather than into the portal venous system .
The SRV inflow to IRVP occurs at about 10 cm distance in lateral wall of rectum and the middle and inferior rectal veins
(IRV) act as the outflowing channels  (Figures 1(a) and 1(b)).
It reaches middle and inferior rectal veins
, which drain to the systemic circulation (inferior vena cava) then into the heart and on to the liver.