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Arteries and Veins of the Pelvis

Complete MBBS Notes - Basics to Advanced

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INTRODUCTION & OVERVIEW

• External iliac artery - becomes the femoral artery at the inguinal ligament
• Internal iliac artery - the main vessel supplying the pelvis

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PART 1: INTERNAL ILIAC ARTERY (Main Pelvic Artery)

Abdominal Aorta (LIV)
        |
   Common Iliac Artery
        |
   _____|_____
   |         |
External    Internal Iliac Artery (LV-SI)
Iliac           |
           _____|_____
           |         |
      Posterior    Anterior
        Trunk        Trunk

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PART 2: POSTERIOR TRUNK - Branches

1. Iliolumbar Artery

• Ascends laterally back out of the pelvic inlet
• Lumbar branch: supplies posterior abdominal wall, psoas and quadratus lumborum muscles, and cauda equina (via a spinal branch through L5-S1 intervertebral foramen)
• Iliac branch: passes into the iliac fossa to supply muscle and bone

2. Lateral Sacral Arteries (usually 2)

• Course medially and inferiorly along the posterior pelvic wall
• Branches pass into the anterior sacral foramina to supply bone and soft tissues, structures in the sacral canal, and skin and muscle posterior to the sacrum
• Anastomoses with the median sacral artery

3. Superior Gluteal Artery

• The largest branch of the internal iliac artery
• Terminal continuation of the posterior trunk
• Passes between lumbosacral trunk and anterior ramus of S1
• Exits through greater sciatic foramen above piriformis
• Enters the gluteal region and supplies gluteal muscles and skin
• Also supplies branches to adjacent pelvic wall muscles and bones

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PART 3: ANTERIOR TRUNK - Branches

Branches Common to Both Male and Female:

1. Umbilical Artery (first branch of anterior trunk)

• Gives origin to the superior vesical artery, then travels forward just inferior to the pelvic inlet margin
• Leaves pelvic cavity and ascends on the internal aspect of the anterior abdominal wall to the umbilicus
• In fetus: large, carries fetal blood to placenta
• After birth: distal portion closes to form the medial umbilical ligament (fibrous cord) - visible as the medial umbilical fold of peritoneum
• Proximal portion remains patent and gives off the superior vesical artery

2. Superior Vesical Artery

• Originates from the root of the umbilical artery
• Courses medially and inferiorly to supply the superior aspect of the bladder and distal ureter
• In men, may also give an artery to the ductus deferens

3. Obturator Artery

• Courses anteriorly along the pelvic wall
• Exits through the obturator canal (with obturator nerve above and obturator vein below)
• Enters the adductor region of the thigh
• Clinical note: An accessory or replaced obturator artery can arise from the inferior epigastric artery ("corona mortis" - "crown of death") - at risk during femoral hernia repair

4. Middle Rectal Artery

• Courses medially to supply the rectum
• Anastomoses with:
  • Superior rectal artery (from inferior mesenteric artery) - above
  • Inferior rectal artery (from internal pudendal) - below

5. Internal Pudendal Artery

• The main artery of the perineum
• Courses inferiorly, exits through the greater sciatic foramen inferior to piriformis
• Associated with the pudendal nerve on its medial side
• Passes laterally to the ischial spine, then through the lesser sciatic foramen to enter the perineum
• Supplies erectile tissues of the clitoris (female) and penis (male)
• Branches in the perineum: inferior rectal artery, perineal artery, dorsal artery of clitoris/penis, deep artery of clitoris/penis

6. Inferior Gluteal Artery

• A large terminal branch of the anterior trunk
• Passes between anterior rami S1-S2 or S2-S3 of sacral plexus
• Exits through greater sciatic foramen inferior to piriformis (same gap as internal pudendal artery and pudendal nerve)
• Enters the gluteal region, supplies gluteal muscles
• Anastomoses with vessels around the hip joint

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PART 4: MALE-SPECIFIC BRANCHES (Anterior Trunk)

Inferior Vesical Artery (Male Equivalent of Vaginal Artery)

• Supplies the bladder, ureter, seminal vesicle, and prostate
• No equivalent female structure - in women this is replaced by the vaginal artery

Summary - Male Anterior Trunk Branches:

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PART 5: FEMALE-SPECIFIC BRANCHES (Anterior Trunk)

Uterine Artery (Female)

• Courses medially and anteriorly in the base of the broad ligament to reach the cervix
• Crosses the ureter (passes superiorly to the lateral vaginal fornix)
• Classic mnemonic: "Water (ureter) under the bridge (uterine artery)"
• Ascends along the lateral margin of the uterus to reach the uterine tube
• Curves laterally and anastomoses with the ovarian artery
• Enlarges significantly during pregnancy
• Through anastomoses, contributes to blood supply of ovary and vagina as well
• Clinical significance: During hysterectomy, the ureter can be accidentally ligated when tying the uterine artery (they cross at the level of the lateral fornix)

Vaginal Artery (Female)

• The female equivalent of the inferior vesical artery in men
• Descends to the vagina
• Supplies branches to the vagina, adjacent parts of the bladder, and rectum
• May originate together with the uterine artery as a common branch, or independently

Ovarian Arteries (Female - Direct Aortic Branches, Not Internal Iliac)

• Originate directly from the abdominal aorta (like testicular arteries in males)
• Travel in the suspensory ligament of the ovary (infundibulopelvic ligament) as they cross the pelvic inlet
• Branches pass through the mesovarium to reach the ovary and through the mesometrium to anastomose with the uterine artery
• Enlarge significantly during pregnancy to augment uterine blood supply

Summary - Female Anterior Trunk Branches:

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PART 6: MEDIAN SACRAL ARTERY

• Originates from the posterior surface of the abdominal aorta just superior to its bifurcation at vertebral level LIV - this is an unpaired direct aortic branch
• Descends in the midline, crosses the pelvic inlet
• Courses along the anterior surface of the sacrum and coccyx
• Gives rise to the last pair of lumbar arteries
• Anastomoses with the iliolumbar and lateral sacral arteries
• Its companion vein drains to the left common iliac vein or the IVC junction

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PART 7: EXTERNAL ILIAC ARTERY (in the Pelvis)

1. Inferior epigastric artery - ascends on the posterior surface of the anterior abdominal wall; anastomoses with the superior epigastric artery
2. Deep circumflex iliac artery - passes laterally to supply the iliac crest region; anastomoses with iliolumbar artery branches

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PART 8: VEINS OF THE PELVIS

General Rule

• Right common iliac vein: ascends along a relatively straight course to the IVC
• Left common iliac vein: runs transversely to join the right iliac vein at an acute angle
• May-Thurner syndrome (Cockett syndrome): compression of the left common iliac vein between the right common iliac artery and vertebra - causes left-sided DVT, predominantly in young-to-middle-aged women

Pelvic Venous Plexuses

Internal Iliac Vein - Tributaries

• Hemorrhoidal (rectal) plexus veins
• Vesicoprostatic plexus (male)
• Uterine veins (female)
• Gonadal veins (variable; usually direct aortic/renal)
• Vesicovaginal plexus (female)

• Superior and inferior gluteal veins
• Sacral veins
• Internal pudendal vein
• Obturator vein
• Sciatic/lumbar veins

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PART 9: RECTAL VENOUS PLEXUS & PORTACAVAL ANASTOMOSIS (High Yield!)

Superior rectal vein  ------>  Inferior mesenteric vein  ------>  PORTAL SYSTEM
Middle rectal vein   ------>  Internal iliac vein        ------>  CAVAL SYSTEM
Inferior rectal vein  ------>  Internal pudendal vein    ------>  CAVAL SYSTEM

Internal Rectal Plexus

• Located in connective tissue between the internal anal sphincter and the epithelium
• Connects superiorly with longitudinal branches of the superior rectal vein in each anal column
• Enlargement = internal hemorrhoids (above pectinate line, covered by colonic mucosa)

External Rectal Plexus

• Circles the external anal sphincter, subcutaneous
• Enlargement = external hemorrhoids (below pectinate line)

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PART 10: DEEP DORSAL VEIN (Male & Female)

• A single deep dorsal vein drains erectile tissues of the penis (male) or clitoris (female)
• Does NOT follow the internal pudendal artery
• Passes directly into the pelvic cavity through a gap between the arcuate pubic ligament and the anterior margin of the perineal membrane
• In men: joins the prostatic plexus of veins
• In women: joins the vesical (bladder) plexus of veins
• Note: Superficial veins draining the skin of the penis/clitoris drain into external pudendal veins → great saphenous vein in the thigh

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PART 11: VEINS THAT LEAVE THE PELVIS VIA THE ABDOMEN

1. Median sacral veins: coalesce into a single vein that joins the left common iliac vein or the IVC junction
2. Ovarian veins (female):
   • Left ovarian vein drains into the left renal vein
   • Right ovarian vein drains directly into the IVC
   • Clinical: Left ovarian vein nutcracker compression can cause pelvic congestion syndrome

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PART 12: KEY CLINICAL CORRELATIONS (MBBS Exam Favourites)

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QUICK REVISION SUMMARY

Arteries - Mnemonic for Internal Iliac Branches

Veins

• Pelvic veins are largely valveless - only 10% of internal iliac veins have valves, 27% of external iliac veins
• Extensive plexuses allow collateral flow in IVC obstruction
• Rectal plexus = most clinically important portacaval anastomosis in the pelvis

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