From Wikipedia, the free encyclopedia
, | ICD9 = , | ICDO = | OMIM = 100070 | MedlinePlus = 000162 | eMedicineSubj = med | eMedicineTopic = 3443 | eMedicine_mult = | MeshID = D017544 | 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 (90%), other possible locations are and . The aneurysm can extend to include one or both of the iliac arteries. An aortic aneurysm may also occur in the thorax.
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.Livesay JJ et al. Milestones in Treatment of Aortic Aneurysm. Tex Heart Inst J 2005; 32: 130–134. PMCID 1163455 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.Famous Patients, Famous Operations, 2002 - Part 3: The Case of the Scientist with a Pulsating Mass from Medscape Surgery
Epidemiology AAA is uncommon in individuals of African, African American, 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). Other risk factors include hypertension and male sex.Treska V. et al.:Aneuryzma břišní aorty, Prague, 1999, ISBN 80-7169-724-9 In the US, the incidence of AAA is 2-4% in the adult population. . Rupture of the AAA occurs in 1-3% of men aged 65 or more, the mortality is 70-95%Lindholt JS, Juul S, Fasting H, Henneberg EW. Screening for abdominal aortic aneurysms: single centre randomised controlled trial. BMJ 2005; 330: 750. PMCID: 555873.
Etiology The exact causes of the degenerative process remain unclear. There are, however, some theories and risk factors defined.
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.
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. Other pathophysiological cause for development of the AAA is inflammation.
Screening A clinical practice guideline by the U.S. Preventive Services Task Force (USPSTF) 'recommends one-time screening for abdominal aortic aneurysm (AAA) by ultrasonography in men age 65 to 75 years who have ever smoked'.ACP Journal Club This is a grade B recommendation. An re-analysis of the meta-analysis estimated a number needed to screen of approximately 850 patients.
In the USA, 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 enrollment 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.Society for Vascular Surgery
The largest of the randomized controlled trials on which this guideline was based studied a screening program that consisted of ACP Journal Club::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 short ( number needed to screen after 4 years of approximately 590 to prevent nonfatal ruptured AAA plus AAA-related deaths) and long term ( number needed to screen after 7 years of approximately 280 to prevent nonfatal ruptured AAA plus AAA-related deaths) benefit and cost effectiveness. ACP Journal Club Subsequent randomized controlled trials also found benefit:
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.
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.[http://www.emedicine.com/emerg/topic27.htm O'Connor RE: Aneurysm, Abdominal], on emedicine, accessed June 23, 2006. 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.
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 75-90%, with 65% of patients dying before they arrive at hospital. The bleeding can be retroperitoneal or intraperitoneal, or the rupture can create an aortocaval or aortointestinal fistula.. Flank ecchymosis is a sign of retroperitoneal hemorrhage, and is also called the Grey-Turner sign.
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 be avoided unless specifically requested by a vascular surgeon.
Treatment The treatment options for asymptomatic AAA are immediate repair, surveillance with a view to eventual repair, and .
There are currently two modes of repair available for an AAA: open aneurysm repair (OR), and endovascular aneurysm repair (EVAR).
Research Stanford University is conducting a study to gather information on AAA risk factors and to determine whether an exercise
program reduces the rate of AAA enlargement.[http://aaastop.stanford.edu]
This article is based on an article from Wikipedia, the free encyclopedia and is available under the terms of GNU Free Documentation License.
In the Wikipedia there is a list with all authors of this article available.