It consists in an anastomosis
between the portal vein and the
interior vena-cava. When the portal
blood is deviated from the vena-cava,
the pressure over the portal system
is diminished and danger from
hemorrhage from esophagus
and gastric varicosity is reduced.
When the vena-cava can not be
used because of an obstruction by
thrombosis or any other reason
one proceeds by a spleen-renal
deviation between the spleen
vena and the renal left vena.