Anatomy of the Retroperitoneum

Lecture given: April 18, 2012


Name the skeletal components of the posterior abdominal wall

Name the muscles of the posterior abdominal wall and state their functions

  • quadratus lumborum
    • From the 12th rib and transvertebral processes to the iliac crest & iliolumbar ligament
    • Kidneys embedded on top
  • Psoas major
    • The only muscle that attach to femor
    • merges with iliac muscle
    • powerful hip flexor
    • pulls on lumbar vertebrae, a common cause of back pain
  • Iliacus
    • from the iliac fossa to the lesser trochanter
    • merge with psoas to form ilia-psoas; assist psoas in hip flexure
  • Transversus abdominis
    • smaller muscle, part of abdominal wall and wraps around
    • comes out transversely towards and merge with abdominal wall anteriorly
    • form part of posterior wall

Describe the structure of the diaphragm and list its attachments

  • Domes up
  • Attach to xyphoid process and arch down to 3rd vertebae, forms part of posterior wall
  • Components: central tendon, peripheral muscle, R&L crura, media, medial and lateral arcuate ligament
  • Central tendon with peripheral muscles
  • Left and right crus attaches to the lumbar vertebrae (Right longer than the left)
  • The median arcuate ligament is formed by the right and left crura of the diaphragm. The crura connect to form an arch, behind which is the aortic hiatus, through which pass the aorta, the azygos vein, and the thoracic duct
  • The medial arcuate ligament is thickening in the fascia that arches over the psoas major muscle as it passes through the diaphragm

State the innervation and blood supply of the diaphragm

  • C3, 4, 5 (phrenic nerve)
  • Phrenic nerve (motor & sensory)
  • Lower intercostals (sensory)
  • Innervation is bilateral, so it's possible to have hemidiaphragm paralysis
  • Blood supply from the internal thoracic artery, branches into:
    • Musculophrenic
    • Pericardiophrenic
  • Aorta branches into inferior phrenic artery

List the main openings in the diaphragm, their vertebral levels and the structures passing through them

  • T8: IVC, right phrenic nerve terminal branch through the central tendon. Caval opening
  • T10: Esophagus, ant & post esophageal plexus (vagus nerve), left gastric vessels passes through the esophageal opening formed by the right crus, creating a sphincter. Also, the splanchnic nerves are pre-ganglionic SNS that enter the abdomen to target GI structures and passes through the crura
  • T12: Aortic hiatus - aorta, azygos, hemiazygos, thoracic duct (drains lymph from lower limbs and abdomen back to IVC).

Describe the course of the abdominal aorta. List its main relations and its branches

  • The median sacral artery is not functionally significant, but tend to bleed a lot. So the surgeons often keep an eye on it during surgery
  • Renal stenosis often caused by AAA. The most common position is juxta-renal, or just under renals

Describe the course of the inferior vena cava and list its main relations and its tributaries

  • Inferior phrenic (paired)
  • Hepatic veins
  • Adrenals (kind of paired)
  • Renal (paired, but left is longer than the right, and receives blood supply from adrenal, gonadal, and inferior phrenic on the left side)
  • Gonadal (kind of paired)
  • Lumbar (paired)
    • Ascending lumbar veins join the azygos
  • Media sacral

The aorta and IVC bifurcates at approx the same level (L4-5), and sit slightly left of the median on the vetebral body
Psoas muscle cross over these vessels. Ureters cross over the psoas, as well as aorta and IVC

Name the main groups of lymph nodes related to the abdominal aorta and its branches

  • preaortic and lumbar lymph nodes
    • Drain abdomnial wall, posterior wall structures (diaphragm, kidney, adrenals, and gonads)
    • Any of the abdominal organs supplied by the abdominal aorta, including those not in the abdominal cavity, such as gonads

Describe the cisterna chyli and list its main afferent lymph channels

Outline the arrangement of sympathetic ganglia and autonomic plexuses as they relate to the posterior abdominal wall

  • If pain in T10-L1, comes from kidney; if T12-L2, comes from ureter. All part of the sympathetic system
  • Renal plexus
  • T5-9: Celiac plexus
  • T8-12: Superior mesenteric
  • T12: Inferior mesenteric
  • L2 & S2-4: Superior and Inferior hypogastric
    • Massive network of neurons
    • Superior hypogastic: located just lower to the inferior mesenteric plexus
    • Inferior hypogastric plexus is located in the artery wall of the rectum and innervates all the genital, reproductive and urinary organs of the pelvis
      • Both ANS and PNS - SNS from L1-2, maybe T12; PNS from S2-4
      • Responsible for incontinence

Define the term "lumbar plexus", list its main branches and outline their functions and territory of supply

  • A network of nerves in the lumbar region. It is formed by the ventral divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12)
# Name Description Landmark
T12 Subcostal Coming out under the last rib 12th rib
L1 iliohypogastric ilioinguinal branches of L1, supply inguinal and lower abdomen area above the pubic region Cross quadratus lumborum
L1-2 Genitofemoral 2 components: genital and femoral. One to thigh, one to genital region. Pulls the genitals up "shrinkage" Pierces psoas
L2-3 Lateral femoral cutaneous coming across iliacus, head to ant. sup. iliac spine (ASUS)
L2-4 Femoral Biggest nerve Lateral to psoas
L2-4 Obturator Hugs lateral wall of pelvis, medial and kind of posterior to psoas

If large abscess on the psoas, might experience:

  • pain on hip flexion
  • weak at flexion due to pressing on femoral nerve
  • back pain
  • stretch or damage or obstruction of ureter


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