The rectal venous plexus consists of an external rectal plexus
that is situated outside to the muscular wall, and an internal rectal plexus''' that is situated in the
submucosa/deep to the mucosa of the rectum and proximal
anal canal at the
anorectal junction.
Internal rectal plexus The internal plexus presents a series of dilated pouches which are arranged in a circle around the tube, immediately above the anal orifice, and are connected by transverse branches. The internal plexus (sources differ) forms'
/is continuous distally/inferiorly with the hemorrhoids (the vascular cushions of the anal canal).'
Venous drainage According to the 42nd edition of ''
Gray's Anatomy'' (2020), the internal rectal plexus is drained mostly by the
superior rectal vein (→
inferior mesenteric vein→
splenic vein→
hepatic portal vein). According to the 8th edition of
Clinically Oriented Anatomy (2017), the internal rectal plexus is drains mostly into the
superior rectal vein superior/proximal to the
pectinate line, and into the
inferior rectal veins (→
internal pudendal vein→
internal iliac vein→
common iliac vein→
inferior vena cava) around the margin of the
external anal sphincter inferior/distal to the pectinate line.
External rectal plexus Venous drainage • The proximal/superior part mostly drains into the
superior rectal vein (→
inferior mesenteric vein→
splenic vein→
hepatic portal vein) • The middle part drains into
middle rectal vein(s) (→
internal iliac vein→
common iliac vein→
inferior vena cava) • The distal/inferior part drains into
inferior rectal veins (→
internal pudendal vein→
internal iliac vein→
common iliac vein→
inferior vena cava)
Structure The veins of the hemorrhoidal plexus are contained in very loose connective tissue, so that they get less support from surrounding structures than most other veins, and are less capable of resisting increased
blood-pressure.
Anastomoses The rectal venous plexus represents a
portosystemic (portocaval) anastomosis.'
The transition from drainage into the portal system to drainage into the inferior caval system occurs in the region of the anal columns.' It communicates anteriorly with the
uterine and
vaginal venous plexus in the female, and with the
vesical venous plexus in the male. == Clinical significance ==