Abdominal aorta.pptx

abdominal aorta : anatomy and discussion of aortic aneurysm.

1. Abdominal aorta Dr Karrar Adil

2. Anatomy : The abdominal aorta is the largest artery in the abdominal cavity. it is a continuation of the thoracic aorta. is a retroperitoneal structure that begins at the hiatus of the diaphragm (the level of the T12 vertebra). It is approximately 13cm long and ends at the level of the L4 vertebra. At this level, the aorta terminates by bifurcating into the right and left common iliac arteries.

3. Relations : Running parallel to the aorta on its right-hand side : the inferior vena cava, the cisterna chyli , the azygos vein, and the para -aortic lymph nodes. Running on its left-hand side : the left sympathetic trunk and the para -aortic lymph nodes. Anteriorly : the stomach, duodenum and pancreas. It is also crossed anteriorly by the splenic vein and the left renal vein . Posteriorly: it is separated from the lumbar vertebrae by the anterior longitudinal ligament and left lumbar veins.

4. Branches : Three single anterior visceral branches : (coeliac trunk, superior mesenteric artery, inferior mesenteric artery ). Three paired lateral visceral branches : ( suprarenal, renal, gonadal arteries). Five paired lateral abdominal wall branches : ( inferior phrenic and four lumbar arteries). Three terminal branches : ( two common iliac arteries and the median sacral artery ).

5. Celiac trunk (T12) : 1- left gastric artery . 2- splenic artery : short gastric arteries (6) splenic arteries. left gastroepiploic a. pancreatic arteries. 3- common hepatic artery : right gastric a. gastroduodenal artery: (right gastroepiploic a. and superior pancreaticoduodenal a .) hepatic artery proper: (right hepatic and left hepatic a .)

6. superior mesenteric artery (L1) : inferior pancreaticoduodenal a. jejunal and ileal arteries right colic a. middle colic a. ileocolic a. inferior mesenteric artery (L3) : left colic a. sigmoid arteries (2 or 3) superior rectal a.

7. The abdominal aorta is clinically divided into 2 segments: The suprarenal abdominal segment , inferior to the diaphragm but superior to the renal arteries. The Infrarenal segment, inferior to the renal arteries and superior to the iliac bifurcation.

8. Abdominal aortic aneurysm

9. Definition : AAA : is a localised , progressive and permanent dilatation occurring in any portion of infra-diaphragmatic aorta. with at least 50% increase in diameter . Most common site is infrarenal aorta. Ectasia : dilatation <50% of normal diameter.

10. Classification : According to wall : true aneurysm : containing the three layers of the arterial wall (intima, media, adventitia) in the aneurysm sac. false aneurysm ( pseudoaneurysm ) : having a single layer of fibrous tissue as the wall of the sac. usually occurs after trauma.

11. According to Location : Infrarenal : below the renal arteries most common (95%). One-third of aneurysms extend into the iliac arteries Suprarenal : above the renal arteries (5%). Isolated suprarenal type is rare; it is usually associated with thoracic and/or infrarenal types.

12. Suprarenal AAA : The aneurysm involves the origins of one or more visceral arteries but does not extend into the chest . Pararenal AAA : The renal arteries arise from the aneurysmal aorta but the aorta at the level of the superior mesenteric artery is not aneurysmal . Juxtarenal AAA : The aneurysm originates just beyond the origins of the renal arteries. There is no segment of nonaneurysmal aorta distal to the renal arteries, but the aorta at the level of the renal arteries is not aneurysmal . Infrarenal AAA : The aneurysm originates distal to the renal arteries. There is a segment of nonaneurysmal aorta that extends distal to the origins of the renal arteries.

13. According to morphology : Fusiform : symmetrical enlargement involving whole circumference of artery. Saccular : affect only part of the arterial circumference. have higher risk of rupture.

14. According to size : Ectatic or mild dilatation : > 2.0 cm and <3.0  cm Moderate : 3.0 - 5.0  cm Large or severe : >5.0 or 5.5 cm According to symptoms : Asymptomatic . Symptomatic. Symptomatic ruptured.

15. Causes : Atherosclerosis : most common cause (95 %) Familial aortic aneurysm (associated with 25% of AAA ). Marfan's , Ehler Danlos syndromes are related genetically. Others : Syphilis , dissection, trauma, collagen diseases, infection , arteritis, cystic medial necrosis. Risk factors : Age , male gender, white race, smoking and family history.

16. Asymptomatic Type : It is found incidentally either on clinical examination or on angiography or on ultrasound. Repair is required if diameter is over 5.5 cm on ultrasound.

17. Symptomatic without Rupture : Clinical features : back pain or abdominal pain (Most common symptom). Abdominal mass which is smooth, soft, non mobile , not moving with respiration, above the umbilical level, resonant on percussion. Common in males ( 4:1 ); common in smokers. GIT , urinary, venous symptoms can also occur. Hypertension , diabetes, cardiac problems should be looked for and dealt with.

18. 5% present as inflammatory aneurysm adherent to ureters, left renal vein, inferior vena cava and duodenum . Aortocaval fistula presents as high output cardiac failure with continuous bruit in abdomen and lower limb edema. Aortoenteric fistula is due to erosion of aneurysm into 4 th part of duodenum presenting as gastrointestinal (GI) bleed, malaena , shock.

19. Symptomatic Ruptured Aortic Aneurysm : Rupture is most common and most lethal complication. AAA rupture most commonly in left retroperitoneum . It may be anterior rupture (20%) into the free peritoneal cavity causing severe shock and death very early. or posterior rupture (80 %) with formation of retroperitoneal haematoma of large size causing severe back pain, hypotension, shock, absence of femoral pulses and with a palpable mass in the abdomen.

20. Diagnosis : Plain X-ray detects AAA in up to 70% cases. CT angiogram (Ix of choice) MRI and MRA is Ix of choice for diagnosis in patients with renal insufficiency. Ultrasound (preferred method of screening).

21. Management : Medical Management : It is done in : low-risk abdominal aortic aneurysm (age below 70 years; active physically without cardiac, respiratory, renal impairment and non inflammatory aneurysm); if aneurysm size is <5 cm . if growth rate is <0.5 cm/year. It includes risk factor modifications : stopping smoking. control of blood pressure and cholesterol. NSAIDs & tetracycline may have potential to reduce aneurysmal growth by inhibiting MMP (Matrix metalloproteinase).

22. Indications of repair of AAA : Diameter 5.5 cm or more in men. Symptomatic aneurysm. For women and patients with greater than average rupture risk, AAA diameter 4.5 to 5.0 cm. Rate of expansion >1 cm/year Atypical aneurysms (dissecting, pseudoaneurysm , mycotic , saccular and penetrating ulcer) regardless of size. Open surgical repair : Transperitoneal & Retroperitoneal approach . endo-aneurysmorrhaphy with intraluminal graft placement.

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