1. ABDOMINAL AORTA AND INFERIOR VENA CAVA
By: Dr. Mujahid Khan

2. Location
Aorta enters the abdomen through the aortic opening of the diaphragm
The opening lies in front of twelfth thoracic vertebra
It descends behind the peritoneum on the anterior surface of the bodies of the lumbar vertebrae

4. Location
On its right side lies the inferior vena cava, the cisterna chyli and beginning of the azygos vein
On the left side lies the left sympathetic trunk
It divides into two common iliac arteries at the level of fourth lumbar vertebra

6. Branches
Three anterior visceral branches: celiac artery, superior and inferior mesenteric arteries
Three lateral visceral branches: suprarenal artery, renal artery, testicular or ovarian artery

8. Branches
Five lateral abdominal wall branches: the inferior phrenic artery and four lumbar arteries
Three terminal branches: two common iliac and the median sacral artery

9. Common Iliac Arteries
Right and left common iliac arteries are the terminal branches of the aorta
They arise at the level of fourth lumbar vertebra
Runs downward and laterally along the medial border of the psoas muscle
Each artery divides into external and internal iliac arteries in front of the sacroiliac joint

11. External Iliac Artery
It runs along the medial border of psoas, following the pelvic brim
It gives off the inferior epigastric and deep circumflex iliac branches
The artery enters the thigh by passing under the inguinal ligament to become the femoral artery

12. Inferior Epigastric Artery
The inferior epigastric artery arises just above the inguinal ligament
Passes upward and medially along the medial margin of the deep inguinal ring
Enters the rectus sheath behind the rectus abdominis muscle

13. Deep Circumflex Iliac Artery
Arises close to the inferior epigastric artery
Ascends laterally to the anterior superior iliac spine and the iliac crest
Supplies the muscles of the anterior abdominal wall

14. Internal Iliac Artery
It passes down into the pelvis in front of the sacroiliac joint

15. Aortic Aneurisms
Localized or diffuse dilatations of the abdominal part of the aorta usually occur below the origin of the renal arteries
Most result from atherosclerosis which causes weakening of the arterial wall
Occur most commonly in elderly men

16. Aortic Aneurisms
Large aneurysms should be surgically excised and replaced with a prosthetic graft
The bifurcation of the abdominal aorta where the lumen suddenly narrows may be a lodging site for an embolus from the heart
Severe ischemia of the lower limbs results

17. Obliteration of Abdominal Aorta and Iliac Arteries
Gradual occlusion of the bifurcation of the abdominal aorta produced by atherosclerosis causes pain in the legs on walking
Impotence may occur due to lack of blood in internal iliac arteries
Surgical treatment by thromboendarterectomy or a bypass graft should be considered

18. Inferior Vena Cava
It conveys most of the blood from the body below the diaphragm to the right atrium of the heart
It is formed by the union of common iliac veins behind the right common iliac artery at the level of fifth lumbar vertebra
It ascends on the right side of the aorta
Pierces the central tendon of the diaphragm at the level of the eighth thoracic vertebra

20. Inferior Vena Cava It drains into the right atrium of the heart
Right sympathetic trunk lies behind its right margin
Right ureter lies close to its right border
The entrance into the lesser sac separates the inferior vena cava from the portal vein

21. Tributaries Two anterior visceral tributaries: the hepatic veins
Three lateral visceral tributaries: the right suprarenal vein, renal veins, right testicular or ovarian vein
Lateral abdominal wall tributaries: inferior phrenic vein and four lumbar veins
Three veins of origin: two common iliac veins and the median sacral vein

23. Trauma to IVC Injuries to inferior vena cava are commonly lethal
The anatomical inaccessibility of the vessel behind the liver, duodenum and mesentery of the small intestine and the blocking presence of the right costal margin make a surgical approach difficult

24. Trauma to IVC
The thin wall of the vena cava makes it prone to extensive tears
Due to the multiple anastomoses of the tributaries of IVC, it is impossible in an emergency to ligate the vessel
Most patients have venous congestion of the lower limbs

25. Compression of IVC
It is commonly compressed by the enlarged uterus during the later stages of pregnancy
This produces edema of the ankles and feet and temporary varicose veins
Malignant retroperitoneal tumors can cause severe compression and eventual blockage of IVC

26. Compression of IVC
This results in the dilatation of the extensive anastomoses of the tributaries
This alternative pathway for the blood to return to the right atrium is referred to as the caval-caval shunt