Pulsatile Abdominal Mass

Presley Regional Trauma CenterDepartment of Surgery

University of Tennessee Health Science CenterMemphis, Tennessee

• Underlying condition may range in severity from benign to life-threatening

• Either attributable to a large blood vessel or from another mass that is simply in close proximity to a blood vessel

General

• AAA = most feared cause of a PAM

• Present in 3 to 9% of population

• 15K deaths per year

• Incidence and penetrance of aneurysms vary according to age and race

General

Presentation

• More common

• Often discovered on abdominal or pelvic scans done for other indications

• Plains films may reveal a calcified aortic shell

Asymptomatic

• Pronounced symptoms

• Condition may range from hemodynamic instability to class IV shock

• Traditional presentation– hypotension– back or abdominal pain– PAM– occurs less than 50% of the time

Ruptured

• Overall mortality = 77 to 94%

• 50% mortality prior to reaching hospital

• Most leak into the left RP = contained rupture

• Free rupture usually results in death either at home or en route to the hospital

Ruptured

• Helpful in determining risk for AAA

• Factor associated with increased risk

– advanced age, greater height, CAD, atherosclerosis, high cholesterol, HTN, smoking duration (7.6x more likely; ex-smokers 3x more likely; RR increases by 4% for each year), male, FH

• Lower risk

– women, African Americans and diabetics

History

Factors

• Occur almost exclusively in elderly males

• Rarely seen in patients younger than 50

– mean age 72

• Male:female = 4:1 to 6:1

• 12 to 19% of patients with AAA will have 1st degree relative with AAA

Risk Factors for Rupture

• Female sex – 2 to 4x more likely

• Larger initial diameter

• Lower FEV1

• Current smoking

• Higher mean bp

Examination

PE

• Key to detecting an AAA prior to the advent of modern radiologic tests

• Palpation of an AAA is safe and has not been reported to precipitate rupture

• Not very accurate in detecting AAA– depends primarily on the size of the AAA– those >5 cm are detectable in 76% of pts

How to Proceed

Unstable Patient

• For the unstable patient with a painful, pulsatile abdominal mass no further study or workup is necessary

• For patients with stable (but not necessarily normal) vitals, CTA can be helpful

Stable Patient

• For the stable patient with a PAM, furhter work-up is always indicated

• Duplex ultrasonography– unreliable in detecting rupture

• CTA of the chest, abdomen and pelvis

Management

Stable Patient

• Once the Dx is made, the subsequent course of action is determined by the clinical presentation and the size

• It must be emphasized that if the patient becomes hemodynamically unstable at any point, operative intervention is necessary

• Must evaluate discomfort and/or pain

No Pain

• Patient with PAM and known AAA

• Hemodynamically stable

• Without complaints of pain

• Must be categorized based on the size of the aneurysm

Pain

• With pain in the abdomen, back, testicles or femoral region, index of suspicion must be high for a symptomatic or ruptured AAA (even if hemodynamically stable)

• Other causes should be considered

• Dx must not be delayed– interval between onset of symptoms and

subsequent Dx and operation may have a direct bearing on overall survival

Considerations

• Whether the risk associated with AAA repair exceeds the risk of rupture in a given period

• What other factors are present that may affect this decision

Indications for Operative Intervention

Basic Physics

• Law of Laplace best describes aneurysm expansion and rupture

• Tangential stress (t) placed on cylinder filled with fluid is determined by

t = Pr/d

• P = pressure exerted by the fluid, r = internal radius of the cylinder and d = thickness of the cylinder wall

So …

• When the aorta expands, its radius increases and wall thickness decreases

– geometric increase in tangential stress

– as an aneurysm grows from 2 to 4 cm in diameter, t increases fourfold

• Elastic tissue in the aorta attenuates with age

• When t > elastic capacity = rupture

Magic Number

5.5 cm

• < 5 cm

• For a patient with a small AAA with stable vitals and no abdominal pain – serial US and optimization of medical management

• Usually do not rupture

• Grow at 0.2 to 0.4 cm per year

Small AAAs

• Over the past several decades, the number of AAAs (especially smaller ones) detected has increased

• Increased serendipitous detection in the course of scans done for other indications

• The progressive aging of the population

Epidemiology

• Evaluating the role various proteolytic enzymes play in processes involving the structural elements in the aortic wall

• Investigating the importance of the immune system, specifically the macrophage, in the development of AAAs

Biology

• Determining how hemodynamic and biomechanical stress affects aortic wall remodeling

• Identifying molecular genetic variables that contribute to AAA development

Biology

• Perioperative β blockade - cardioprotective

• Anti-HTN – no level I data

• Lipid-lowering drugs – requires further study

­ long-term statin use after successful AAA surgery has been associated with reduced mortality

• Smoking cessation = mandatory

Medical Therapy

Pre-op Evaluation

• Must determine expected benefit of repair in relation to the estimated risk

• Detailed H&P

• ECG

• Routine lab work

• Appropriate imaging - approach

• Optimize patient medically

Elective AAA

Comorbid Conditions

CAD

• Common

• Leading cause of both early and late mortality after AAA repair

• ACC/AHA guidelines

• Clinical predictors of major perioperative CV risk – defined as MI, CHF or death – may be divided into 3 categories

– major, intermediate and minor

Significance

• Major predictor requires that the Sx or disease be managed appropriately before non-emergency surgery

• Intermediate predictor is associated with increased risk of periop cardiac complications and requires current status be fully investigated

Significance

• Minor predictor is indicative of CV disease but has not been shown to independently increase the risk of periop CV complications

• Once clinical predictors have been evaluated, additional factors involving the patient’s ability to perform various activities (from ADLs to strenuous sports)

METs

• Quantification of the energy required to perform an activity = metabolic equivalents

• The number of METs of which a patient is capable directly correlates with the ability to perform specific tasks

• Patients who are unable to attain 4 METs are considered to be at high risk for periop Cv events and long-term complications

Benefit

• 2 large RCT to evaluate if pre-op coronary intervention (CABG or PTCA) improved mortality in elective major vascular surgery

• No difference with respect to periop (30 days) MI in either group

• At 2.7 years there was no difference in mortality between the groups

So …

• There is no need of pre-op coronary revascularization in patients with stable CAD

• In stable patients, without evidence of heart failure, there may be no role for pre-op intervention as long as aggressive medical therapy can be initiated