General characteristics of the pelvic veins
The pelvic venous system is represented by three main vessels: the common iliac vein (vena iliaca communis), internal iliac vein (vena iliaca interna), and external iliac vein (vena iliaca externa). The topography and blood drainage zones of these veins largely correspond to the arteries of the same name, which facilitates learning when relying on knowledge of arterial angiology.
The common iliac vein is formed by the confluence of the internal and external iliac veins. The right and left common iliac veins unite to form the inferior vena cava. The only independent tributary of the common iliac vein is the vena sacralis mediana — the median sacral vein, a rudimentary vessel accompanying the artery of the same name.
Internal iliac vein: parietal tributaries
The internal iliac vein collects blood from the walls and organs of the lesser pelvis. Its parietal tributaries follow the course of the corresponding branches of the internal iliac artery:
- The superior and inferior gluteal veins (venae gluteae superior et inferior) exit the gluteal region through the suprapiriform and infrapiriform foramina;
- The obturator vein (vena obturatoria) accompanies the obturator artery; unlike the arterial system, a venous "corona mortis" is not described in anatomy;
- The lateral sacral veins (venae sacrales laterales) are numerous vessels located along the sacrum;
- The iliolumbar vein (vena iliolumbalis) accompanies the artery of the same name.
Visceral tributaries and venous plexuses of the lesser pelvis
The visceral tributaries of the internal iliac vein originate from the venous plexuses of the pelvic organs. These plexuses evolved to simplify the nomenclature of the dense network of small veins.
- The sacral venous plexus (plexus venosus sacralis) is an anastomosis between the lateral and median sacral veins;
- The prostatic venous plexus (plexus venosus prostaticus) in males collects blood from the prostate gland and seminal vesicles; it receives the vena dorsalis profunda penis, deep veins of the penis, and posterior scrotal veins (venae scrotales posteriores);
- The vaginal venous plexus (plexus venosus vaginalis) in females continues into the uterine venous plexus (plexus venosus uterinus), with outflow passing through the uterine veins (venae uterinae);
- The vesical venous plexus (plexus venosus vesicalis) drains via the vesical veins (venae vesicales);
- The rectal venous plexus (plexus venosus rectalis) is the largest; its pathological dilation manifests as hemorrhoids.
Features of outflow from the rectal plexus
Blood drains from the rectal venous plexus via three veins — one unpaired superior and paired middle and inferior veins:
- The superior rectal vein (vena rectalis superior) empties into the inferior mesenteric vein and further into the portal vein system;
- The middle rectal vein (vena rectalis media) empties into the internal iliac vein, including via the internal pudendal vein (vena pudenda interna);
- The inferior rectal vein (vena rectalis inferior) also belongs to the internal iliac vein basin.
Thus, the rectal plexus is an important portacaval anastomosis connecting the portal venous system with the inferior vena cava system.
External iliac vein
The external iliac vein (vena iliaca externa) is the direct continuation of the femoral vein (vena femoralis). The boundary between them passes along the inguinal ligament in the region of the vascular lacuna. The main function of the external iliac vein is to receive blood from the lower limb and direct it into the common iliac vein, and further into the inferior vena cava and right atrium.
The tributaries of the external iliac vein correspond to the branches of the artery of the same name:
- The inferior epigastric vein (vena epigastrica inferior) anastomoses with the superior epigastric vein (vena epigastrica superior), a tributary of the internal thoracic vein, forming a cavacaval anastomosis;
- The deep circumflex iliac vein (vena circumflexa iliaca profunda) accompanies the artery of the same name.
Key points
- The pelvic veins include the common, internal, and external iliac veins; their topography mirrors the arteries of the same name.
- The common iliac vein has only one proper tributary — the median sacral vein.
- Parietal tributaries of the internal iliac vein: gluteal, obturator, lateral sacral, and iliolumbar veins.
- Visceral tributaries originate from five venous plexuses: sacral, prostatic (or vaginal and uterine), vesical, and rectal.
- The rectal plexus is clinically significant as the site where hemorrhoids develop.
- The superior rectal vein provides a portacaval anastomosis via the inferior mesenteric vein.
- The external iliac vein is the continuation of the femoral vein and collects blood from the lower extremity.
- The inferior epigastric vein participates in the formation of a cavacaval anastomosis with the superior epigastric vein.