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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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