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16-September-2008 16:15:12 - aortic aneurysm Abdominal aortic aneurysm Classification and external resources ICD-10 I71.3, I71.4 ICD-9 441.3, 441.4 OMIM 100070 DiseasesDB 792 MedlinePlus 000162 eMedicine med/3443 emerg/27 radio/1 MeSH D017544 A plate from Gray's Anatomy with yellow lines depicting the most common infrarenal location of the AAA. A plate from Gray's Anatomy with yellow lines depicting the most common infrarenal location of the AAA. Abdominal aortic aneurysm, also written as AAA and often pronounced 'triple-A', is a localized dilatation of the abdominal aorta, that exceeds the normal diameter by more than 50%. The normal diameter of the infrarenal aorta is 2 cm. It is caused by a degenerative process of the aortic wall, however the exact etiology remains unknown. It is most commonly located below the kidneys infrarenally; 90%, other possible locations are above or at the level of the kidneys suprarenal and pararenal. The aneurysm can extend to include one or both of the iliac arteries. An aortic aneurysm may also occur in the thorax. An abdominal aortic aneurysm occurs most commonly in older individuals between 65 and 75, and more in men and smokers. There is moderate evidence to support screening in individuals with these risk factors. The majority of abdominal aortic aneurysms do not cause symptoms. Symptomatic and large aneurysms 5 cm in diameter are considered for repair. The most important complication of an abdominal aortic aneurysm is rupture, which is most often a fatal event. An abdominal aortic aneurysm weakens the walls of the blood vessel, leaving it vulnerable to bursting open, or rupturing, and spilling large amounts of blood into the abdominal cavity.1 Contents 1 History 2 Epidemiology 3 Etiology 4 Pathophysiology 5 Screening 6 Manifestations and Diagnosis 7 Rupture 8 Treatment 9 References History The first historical records about AAA are from Ancient Rome, more precisely from the 2nd century AD, when Greek surgeon Antyllus tried to treat the AAA with proximal and distal ligature, central incision and evacuation of thrombotic material from the aneurysm. However, attempts to treat the AAA surgically were unsuccessful until 1923. In that year, Rudolph Matas who also proposed the concept of endoaneurysmorrhaphy, performed the first successful aortic ligation on a human.2 Other methods that were successful in treating the AAA included wrapping the aorta with polyethene cellophane, which induced fibrosis and restricted the growth of the aneurysm. Albert Einstein was operated on by Rudolf Nissen with use of this technique in 1949, and survived five years after the operation.3 Epidemiology AAA is uncommon in individuals of African, Asian, and Hispanic heritage. The frequency varies strongly between males and females. The peak incidence is among males around 70 years of age, the prevalence among males over 60 years totals 2-6%. The frequency is much higher in smokers than in non-smokers 8:1, and the risk decreases slowly after smoking cessation.4 Other risk factors include hypertension and male sex.5 In the U.S., the incidence of AAA is 2-4% in the adult population. 6. AAA is 4-6 times more common in male siblings of known patients, with a risk of 20-30%.7 Rupture of the AAA occurs in 1-3% of men aged 65 or more, the mortality is 70-95%.8 Etiology The exact causes of the degenerative process remain unclear. There are, however, some theories and risk factors defined. Genetic influences: The influence of genetic factors is highly probable. The high familial prevalence rate is most notable in male individuals.9 There are many theories about the exact genetic disorder that could cause higher incidence of AAA among male members of the affected families. Some presumed that the influence of alpha 1-antitrypsin deficiency could be crucial, some experimental works favored the theory of X-linked mutation, which would explain the lower incidence in heterozygous females. Other theories of genetic etiology were also formulated.6 Hemodynamic influences: Abdominal aortic aneurysm is a focal degenerative process with predilection for the subrenal aorta. The histological structure and mechanical characteristics of subrenal aorta differ from those of the thoracic aorta. The diameter decreases from the root to the bifurcation, and the wall of the abdominal aorta also contains a lesser proportion of elastin. The mechanical tension in abdominal aortic wall is therefore higher than in the thoracic aortic wall. The elasticity and distensibility also decline with age, which can result in gradual dilatation of the segment. Higher intraluminal pressure in patients with arterial hypertension markedly contributes to the progression of the pathological process.5 Atherosclerosis: The AAA was long considered to be caused by atherosclerosis, because the walls of the AAA are frequently affected heavily. However, this theory cannot be used to explain the initial defect and the development of occlusion, which is observed in the process.6 Other causes: Other causes of the development of AAA include: infection, trauma, arteritis, cystic medial necrosis m. Erdheim and connective tissue disorders e.g. Marfan syndrome, Ehlers-Danlos syndrome.5 Pathophysiology The most striking histopathological changes of aneurysmatic aorta are seen in tunica media and intima. These include accumulation of lipids in foam cells, extracellular free cholesterol crystals, calcifications, ulcerations and ruptures of the layers and thrombosis. There is an adventitial inflammatory infiltrate.5 However, the degradation of tunica media by means of proteolytic process seems to be the basic pathophysiologic mechanism of the AAA development. Some researchers report increased expression and activity of matrix metalloproteinases in individuals with AAA. This leads to elimination of elastine from the media, rendering the aortic wall more susceptible to the influence of the blood pressure. 6 Other pathophysiological cause for development of the AAA is inflammation. Screening A clinical practice guideline by the U.S. Preventive Services Task Force recommends one-time screening for abdominal aortic aneurysm AAA by ultrasonography in men age 65 to 75 years who have ever smoked.1011 This is a grade B recommendation12. A re-analysis of the meta-analysis estimated a number needed to screen of approximately 850 patients.13 The largest of the randomized controlled trials on which this guideline was based studied a screening program that consisted of14: Screening men ages 65-74 years not restricted to ever smokers. 'Men in whom abdominal aortic aneurysms or =3 cm in diameter were detected were followed-up... Patients with an aortic diameter of 3·0-4·4 cm were rescanned at yearly intervals, whereas those with an aortic diameter of 4·5-5·4 cm were rescanned at 3-monthly intervals ... Surgery was considered on specific criteria diameter or =5.5 cm, expansion or =1 cm per year, symptoms'. This trial reported significant short14 number needed to screen after 4 years of approximately 590 to prevent nonfatal ruptured AAA plus AAA-related deaths15 and long term16 number needed to screen after 7 years of approximately 280 to prevent nonfatal ruptured AAA plus AAA-related deaths benefit and cost effectiveness.17 Subsequent randomized controlled trials also found benefit: number needed to screen after 4 years of 30018 number needed to screen after and after 7 years of 563 calculation.19 In the U.S., effective January 1, 2007, provisions of the SAAAVE Act Screening Abdominal Aortic Aneurysm Very Efficiently now provide a free, one-time, ultrasound AAA screening benefit for those qualified seniors. Men who have smoked at least 100 cigarettes during their life, and men and women with a family history of AAA qualify for the one-time ultrasound screening. Enrollees must visit their healthcare professional for their Welcome to Medicare physical within six months of enrolment in order to qualify for the free screening. The Welcome to Medicare Physical Exam must be completed within the first six months of Medicare eligibility, but there is no published time limit thereafter for completion of the AAA screening. Providers who perform the physical and order the AAA screening need to document the AAA risk factors.20 Manifestations and Diagnosis AAAs are commonly divided according to their size and symptomatology. An aneurysm is usually considered to be present if the measured outer aortic diameter is over 3 cm normal diameter of aorta is around 2 cm. The natural history is of increasing diameter over time, followed eventually by the development of symptoms usually rupture. If the outer diameter exceeds 5 cm, the aneurysm is considered to be large. For aneurysms under 5 cm, the risk of rupture is low, so that the risks of surgery usually outweigh the risk of rupture. Aneurysms less than 5cm are therefore usually kept under surveillance until such time as they become large enough to warrant repair, or develop symptoms.58 The vast majority of aneurysms are asymptomatic. The risk of rupture is high in a symptomatic aneurysm, which is therefore considered an indication for surgery. Possible symptoms include low back pain, flank pain, abdominal pain, groin pain or pulsating abdominal mass.21 The complications include rupture, peripheral embolisation, acute aortic occlusion, aortocaval or aortoduodenal fistulae. On physical examination, a palpable abdominal mass can be noted. Bruits can be present in case of renal or visceral arterial stenosis.6 CT image showing an abdominal aortic aneurysm. CT image showing an abdominal aortic aneurysm. As most of the AAAs are asymptomatic, their presence is usually revealed during an abdominal examination for another reason - the most common being abdominal ultrasonography. A physician may also detect the presence of an AAA by abdominal palpation. Ultrasonography provides the initial assessment of the size and extent of the aneurysm, and is the usual modality for surveillance. Preoperative examinations include CT, MRI and special modes thereof, like CT/MR angiography. Angiography may be useful also, as an additional method of measurement for the planning of endoluminal repair. Note that an aneurysmal aorta may appear normal on angiogram, due to thrombus within the sac. Rupture The clinical manifestation of ruptured AAA can include low back, flank, abdominal or groin pain, but the bleeding usually leads to a hypovolemic shock with hypotension, tachycardia, cyanosis, and altered mental status. The mortality of AAA rupture is up to 90%. 65-75% of patients die before they arrive at hospital and up to 90% die before they reach the operating room.22 The bleeding can be retroperitoneal or intraperitoneal, or the rupture can create an aortocaval or aortointestinal fistula.5. Flank ecchymosis appearance of a bruise is a sign of retroperitoneal hemorrhage, and is also called the Grey-Turner sign.6 Ruptured AAA is a clinical diagnosis: the presence of the triad of abdominal pain, shock and pulsatile abdominal mass makes the diagnosis; no further investigations are required for diagnostic purposes, and imaging should not delay surgery. The operative mortality has slowly decreased over several decades but remains higher than 40%.23 Treatment The treatment options for asymptomatic AAA are immediate repair, surveillance with a view to eventual repair, and conservative management. There are currently two modes of repair available for an AAA: open aneurysm repair OR, and endovascular aneurysm repair EVAR. Conservative treatment is indicated in patients where repair carries a high risk of mortality and also in patients where repair is unlikely to improve life expectancy. The two mainstays of the conservative treatment are smoking cessation and blood pressure control. Recent studies have suggested possible protective effects of therapy with angiotensin converting enzyme inhibitors or statins.2425 Surveillance is indicated in small aneurysms, where the risk of repair exceeds the risk of rupture. As an AAA grows in diameter the risk of rupture increases. Surveillance until the aneurysm has reached a diameter of 5cm has not been shown to have a higher risk as compared to early intervention.2627 The threshold for repair varies slightly from individual to individual, depending on the balance of risks and benefits when considering repair versus ongoing surveillance. The size of an individual's native aorta may influence this, along with the presence of comorbitities that increase operative risk or decrease life expectancy. Open repair operation is indicated in young patients as an elective procedure, or in growing or large, symptomatic or ruptured aneurysms. Open repair has been the mainstay of intervention from the 1950s until recently. Endovascular repair first became practical in the 1990s and although it is now an established alternative to open repair, its role is yet to be clearly defined. It is generally indicated in older, high-risk patients or patients unfit for open repair. However, endovascular repair is feasible for only a proportion of AAA's, depending on the morphology of the aneurysm. The main advantage over open repair is that there is less peri-operative mortality, less time in intensive care, less time in hospital overall and earlier return to normal activity. Disadvantages of endovascular repair include a requirement for more frequent ongoing hospital reviews, and a higher chance of further procedures being required. According to the latest studies, the EVAR procedure doesn't offer any benefit for overall survival or health-related quality of life compared to open surgery, although aneurysm-related mortality is lower.28293031 In patients unfit for open repair, EVAR plus conservative management was associated with no benefit and more complications and subsequent procedures and higher costs compared to conservative management alone.32 New endovascular devices are being developed that are able to treat more complex and tortuous anatomies.33 References ^ Upchurch GR, Schaub TA 2006. Abdominal aortic aneurysm. Am Fam Physician 73 7: 1198-204. PMID 16623206. ^ Livesay JJ et al. Milestones in Treatment of Aortic Aneurysm. Tex Heart Inst J 2005; 32: 130-134. PMCID 1163455 ^ Famous Patients, Famous Operations, 2002 - Part 3: The Case of the Scientist with a Pulsating Mass from Medscape Surgery ^ Wilmink TBM, Quick CRG, Day NE. The association between cigarette smoking and abdominal aortic aneurysms. J Vasc Surg 1999;30:1099-1105. PMID 10587395 ^ a b c d e f Treska V. et al.:Aneuryzma břišní aorty, Prague, 1999, ISBN 80-7169-724-9 ^ a b c d e f med/3443 at eMedicine ^ Baird PA, Sadovnick AD, Yee IM, Cole CW, Cole L. Sibling risks of abdominal aortic aneurysm. Lancet 1995;346:601-604. PMID 7651004 ^ a b Lindholt JS, Juul S, Fasting H, Henneberg EW. Screening for abdominal aortic aneurysms: single centre randomised controlled trial. BMJ 2005; 330: 750. PMCID: 555873 ^ Clifton, MA: Familial abdominal aortic aneurysms. Br. J. Surg., 64, 1977, p. 765-766 ^ U.S. Preventive Services Task Force 2005. Screening for abdominal aortic aneurysm: recommendation statement. Ann. Intern. Med. 142 3: 198-202. PMID 15684208. ^ Fleming C, Whitlock EP, Beil TL, Lederle FA 2005. Screening for abdominal aortic aneurysm: a best-evidence systematic review for the U.S. Preventive Services Task Force. Ann. Intern. Med. 142 3: 203-11. PMID 15684209. ACP Journal Club ^ Recommendation ratings ^ Cinà CS, Devereaux PJ 2005. Review: population-based screening for abdominal aortic aneurysm reduces cause-specific mortality in older men. ACP J. Club 143 1: 11. PMID 15989299. ^ a b Ashton HA, Buxton MJ, Day NE, et al 2002. The Multicentre Aneurysm Screening Study MASS into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial. Lancet 360 9345: 1531-9. PMID 12443589. ACP Journal Club ^ Cina CS 2003. Screening for abdominal aortic aneurysm reduced death from AAA in older men. ACP J. Club 138 3: 66. PMID 12725621. ^ Kim LG, P Scott RA, Ashton HA, Thompson SG 2007. A sustained mortality benefit from screening for abdominal aortic aneurysm. Ann. Intern. Med. 146 10: 699-706. PMID 17502630. ^ Multicentre Aneurysm Screening Study Group 2002. Multicentre aneurysm screening study MASS: cost effectiveness analysis of screening for abdominal aortic aneurysms based on four year results from randomized controlled trial. BMJ 325 7373: 1135. doi:10.1136/bmj.325.7373.1135. PMID 12433761. ACP Journal Club ^ Lindholt JS, Juul S, Fasting H, Henneberg EW 2005. Screening for abdominal aortic aneurysms: single centre randomised controlled trial. BMJ 330 7494: 750. doi:10.1136/bmj.38369.620162.82. PMID 15757960. ACP Journal Club ^ Ashton HA, Gao L, Kim LG, Druce PS, Thompson SG, Scott RA 2007. Fifteen-year follow-up of a randomized clinical trial of ultrasonographic screening for abdominal aortic aneurysms. The British journal of surgery 94 6: 696-701. doi:10.1002/bjs.5780. PMID 17514666. ^ Society for Vascular Surgery ^ O'Connor RE: Aneurysm, Abdominal, on emedicine, accessed June 23, 2006. ^ Brown LC, Powell JT, UK Small Aneurysm Trial Participants. Risk factors for aneurysm rupture in patients kept under ultrasound surveillance. Ann Surg 1999;230:289-297. PMID 10493476 ^ Bown MJ, Sutton AJ, Bell PR, Sayers RD. A meta-analysis of 50 years of ruptured abdominal aortic aneurysm repair. Br J Surg 2002;89:714-730. PMID 12027981 ^ Hackam DG, Thiruchelvam D, Redelmeier DA. Angiotensin-converting enzyme inhibitors and aortic rupture: a population-based case-control study. Lancet 2006;368:659-665. PMID 16920471 ^ Powell JT, Brown LC, Greenhalgh RM, Thompson SG. The rupture rate of large abdominal aortic aneurysms: is this modified by anatomical suitability for endovascular repair? Ann Surg 2008;247:173-179. PMID 18156938 ^ Powell JT, Brown LC, Forbes JF, et al. Final 12-year follow-up of patients enrolled in the UK Small Aneurysm Trial. Br J Surg 2007;94:702-708. PMID 17514693 ^ Lederle FA, Wilson SE, Johnson GR, et al. Immediate repair compared with surveillance of small abdominal aortic aneurysms. N Engl J Med 2002;346:1437-1444. PMID 12000813 Free full text ^ Rutherford RB. Randomized EVAR Trials and Advent of Level I Evidence: A Paradigm Shift in Management of Large Abdominal Aortic Aneurysms? Semin Vasc Surg 2006; 19:69-74. PMID 16782510 ^ Lederle FA, Kane RL, MacDonald R, Wilt TJ 2007. Systematic review: repair of unruptured abdominal aortic aneurysm. Ann. Intern. Med. 146 10: 735-41. PMID 17502634. ^ EVAR Trial Participants. Endovascular aneurysm repair versus open repair in patients with abdominal aortic aneurysm EVAR trial 1: randomised controlled trial. Lancet 2005;365:2179-2186. PMID 15978925 ^ Blankensteijn JD, de Jong SECA, Prinssen M, et al. Two-year outcomes after conventional or endovascular repair of abdominal aortic aneurysms. N Engl J Med 2005;352:2398-2405. PMID 15944424 Free full text ^ EVAR Trial Participants. Endovascular aneurysm repair and outcome in patients unfit for open repair of abdominal aortic aneurysm EVAR trial 2: randomised controlled trial. Lancet 2005;365:2187-2192. PMID 15978926 ^ Albertini JN, Perdikides T, Soong CV, Hinchliffe RJ, Trojanowska M, Yusuf SW, Endovascular repair of abdominal aortic aneurysms in patients with severe angulation of the proximal neck using a flexible stent-graft: European Multicenter Experience. J Cardiovasc Surg Torino. 2006;473:245-50. PMID 16760860 v d e Cardiovascular disease: vascular disease - Circulatory system pathology I70-I99, 440-459 Arteries, arterioles and capillaries Arterial occlusive disease Arteriosclerosis: Atherosclerosis - Intermittent claudication - Atheroma - Monckeberg's arteriosclerosis Stenosis Renal artery stenosis, Carotid artery stenosis - Fibromuscular dysplasia - Degos disease - Aortoiliac occlusive disease Peripheral vascular disease Raynaud's phenomenon/Raynaud's disease - Erythromelalgia Aneurysm Aortic aneurysm/Abdominal aortic aneurysm - Cerebral aneurysm - Coronary artery aneurysm - Intracranial berry aneurysm - Dissection Aortic, Carotid, Vertebral - Pseudoaneurysm Other Arteritis Aortitis - Buerger's disease Arteriovenous fistula - Herary hemorrhagic telangiectasia Nevus Spider angioma, Halo nevus Veins Venous thrombosis/ Phlebitis/ Thrombophlebitis primarily lower limb Deep vein thrombosis abdomen May-Thurner syndrome, Portal vein thrombosis, Budd-Chiari syndrome, Renal vein thrombosis upper limb Paget-Schroetter disease head Cerebral venous sinus thrombosis Post-thrombotic syndrome Varicose veins Varicocele - Gastric varices - Portacaval anastomosis Hemorrhoid, Esophageal varices, Caput medusae Other Superior vena cava syndrome - Inferior vena cava syndrome - Venous ulcer Arteries or veins Vasculitis - Thrombosis - Embolism Pulmonary embolism, Cholesterol embolism - Angiopathy Macroangiopathy, Microangiopathy Lymphatic disease Lymphadenitis - Lymphedema - Lymphangitis Blood pressure Hypertension Hypertensive heart disease - Hypertensive nephropathy - Secondary hypertension Renovascular hypertension - Pulmonary hypertension Hypotension Orthostatic hypotension See also congenital, neoplasia Retrieved from http://en..org/wiki/Abdominal_aortic_aneurysm Categories: Vascular surgery | Surgery | Cardiovascular diseases Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages Italiano This page was last modified on 25 July 2008, at 11:31
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