Abdominal Aortic Aneurysm

Key Feature


Abdominal Aortic Aneurysm


Essentials Of Diagnosis

  • Defined as an aortic diameter > 3 cm.
  • Most are asymptomatic,detected during a routine physical examination or imaging performed for anoother reason 
  • Sever back and abdominal pain and hypotension indicate rupture
  • Concomitant atherosclerotic occlusive disease of lower extremities in 25 %
General Considerations

  • More then 90% of abdominal aneurysms originate below the renal arteries many extend into the common iliac arteries.
  • Half are <5 Cm in diameter.
  • On routine ultrasound surveillance,two third will increase in size to require repair.
  • Yearly rupture risk is 2% for 4 to 5.4 cm aneurysms ,7% for 6 to 6.9 cm aneurysms,25% for 7 cm aneurysms
  • Patients with chronic obstructive pulmonary disease are more likely to experience rupture are small aneurysms.
  • More then one third of patients with popliteal aneurysms have abdominal aortic aneurysms. 
Demographic
  • Aortic aneurysms is present in 5-8% of the population older than 65.
  • Incidence has tripled over the last 30 years. 
Clinical Finding

Symptoms & Signs
  • Asymptomatic aneurysms prominent aortic pulsation on routine physical examination and incidental finding on abdominal ultrasonogram or CT scan,coexisting renal or lower extremity arterial occlusive disease present in 25% ,popliteal artery aneurysms in 15%.
  • Symptomatic aneurysms : midabdominal or lower back pain (or both).
  • Inflammatory aortic aneurysms : Low grade fever,elevated sedimentation rate and recent upper respiratory tract infection.
  • Infected aneurysms (rare) : Fever of unknown origin.peripheral emboli,positive blood cultures,caused by septic emboli to a normal aorta or bacterial colonization of an exisiting aneurysms.
  • Ruptured aneurysms : Severe back,abdominal or flank pain and hypotension ; 90% patients die before reaching the hospital are in the perioperative period.
Differential Diagnosis 
  • Asymptomatic abdominal aortic aneurysms: intraabdominal tumor,iliac aneurysms,Or mesenteric artery aneurysms.
  • Symptomatic/Ruture abdominal aortic aneurysms: acute myocardial infarction,Aortic dissection,Renal stones,Gastrointeritis,Bowel obstruction,and bowel infarction.
Diagnosis
Laboratory Tests
preoperative evaluation : Electrocardiogram,Serum Creatinine,Hematocrit and Hemoglobin and type and acrsross match.

Imaging Studies


  • Abdominal Ultrasonography : Indicated for screening and for monitoring aneurysm growth (annually for aneurysms > 3.5 cm in diameter)
  • Abdominal Radiograph : Curvilinear calcification are much less accurate
  • Contrast - enhanced CT scanning : precisely sizes the aneurysm,define it`s relationship to the renal arteries.
  • MRI : as sensitive and specific as CT and useful is renal insufficiency precludes contrast-enhanced CT.
  • Aortography/CT angiogram : indicated before elective aneurysmrepair when arterial occlusive disease of the visceral or lower extremity arteries is suspected or when endograft repair is being considerd .
  • Preoperative Evaluation : Assessment of cardiac risk and ultrasound examination of the carotid arteries.

Medication

  • Beta-Blocker and oral Roxithromycin ,300 mg daily for 30 days,Decrease the expansion rate of small  aneurysm.

Surgery

  • In asymptomatic good risk patients,surgery advised when  aneurysm diameter > 5 cm.
  • In poor risk patients,surgery advised when  aneurysm diameter > 6 cm.
  • Urgent repair advised for symptomatic  aneurysms irrespective diameter.
  • Ruptured  aneurysms require emergent surgery.
  • Open repair : Surgical reaction and synthetic graft replacement for most thoracic,abdominal,juxtarenal,and infrarenal aortic  aneurysms with diameter > 5 cm.
  • Endovascular Repair : Uniiliac or bifurcated endovascular stent grafts,deployed via the common femoral arteries,can be considered for infrarenal  aneurysms with favorable anatomy.
  • Endovascular repair can be done by a percutaneous route or by bilateral inguinal incisions under epidural anesthesia,and thus has made repair of aortic  aneurysms feasible in elderly high risk patients.
  • Long-Term durability of endovascular grafts needs to be established.

Therapeutic procedure 

  • Physical examination.
  • Ultrasonogram of abdominal aorta every 6 month.

Follow Up

  • Open repair : Yearly physical examination.
  • Endovascular repair : Routine surveillance,CT abdomen,and physical examination.

Complication

  • Open repair : Acute myocardial infraction,Arrhythmia,Bleeding,Respiratory failure,Limb ischemia,Renal failure,stroke,Ischemic colitis,Bowel infraction,Liver dysfunction,acalculous cholecystitis,Grafts infaction,Graft enteric fistula.
  • Endovascular Repair : Persistent filling of the  aneurysm(Endoleak),Graft Migration,Graft Thrombosis,Graft Infaction (Rare),Renal failure,conversion to open repair.

Prognosis

  • Mortality following elective open or endovascular repair is 1-5 %
  • A patient with >5 cm aortic aneurysmand life expectancy of > 1 year has a 3 fold greater chance of dying of rupture than of dying from surgical reaction .
  • 5 year survival after surgical repair is 60-80 %.
  • 5-10 will develop another aortic aneurysm adjacent to the graft or in the thoracic aorta.

When to Refer

  • Any patient with an aneurysm_> 4.0 cm .
  • Any patient with a symptomatic or suspected ruptured abdominal aortic aneurysm.

When to Admit

  • All patients with symptomatic or suspected ruptured abdominal aortic aneurysms or suspected infected aneurysms.

Prevention

  • Blood pressure Control.
  • Cardiovascular risk assessment and treatment.
  • Smoking cessation .
  • Screening of family members older than 65.

Evidence

Practice Guidelines

  • Brewster DC et al : Guideline for the treatment of abdominal aortic aneurysms.Report of a subcommittee of the joint Council of the American association for the vascular surgery and Society for Vascular surgery.



0 comments:

Post a Comment