Rupture of abdominal aortic aneurysm

rupture of abdominal aortic aneurysm

AAA rupture is defined as bleeding outside the adventitia of a dilated aortic wall.

• it is the most important complication of AAA and is a medical emergency
• rupture is related to wall tension which is in turn related to radius by Laplaces law.
• as aneurysms increase in size, the risk of rupture also increases e.g if diameter is 5cm the absolute life time risk of rupture is 20%. This increases to 50% when the diameter reaches 7cm (2)

The incidence of ruptured abdominal aortic aneurysms ranges between 5.6 and 17.5 per 100,000 person-years in Western countries

• this number seems to be declining over the last decade
  • aneurysm ruptures dropped from 18.7/100,000 (in 1994) to 13.6/100,000 (in 2003) in the USA
• however the overall mortality is still very high - around 80%-90%
• the operative mortality rates are between 32% to 80% (1)

Rupture results in haemorrhage and may be:

• free rupture in the peritoneal cavity
  
  
• retroperitoneal rupture where the retroperitoneal tissue provides tamponade and reduces temporarily the volume of blood loss

Rupture results in haemorrhage. This may:

• be limited by the peri-aortic soft tissues presenting with severe abdominal pain without hypovolaemia
• extend into the peritoneal cavity resulting in:
  • a tender pulsating abdominal mass
  • clinical signs of hypovolaemia
  • abdominal or back pain
• extend into the gut (third part of duodenum), inferior vena cava (producing high output cardiac failure) or the left renal vein.

It is very important to differentiate between symptomatic and ruptured aneurysms.

• symptomatic AAAs are those that have become painful but without breach of the aortic wall
• in ruptured AAA patients may present with the classic clinical triad of : hypotension, shooting abdominal or back pain and a pulsatile abdominal mass
  • this classic triad may be incomplete or absent in some patients (2)

Management of ruptured aneurysm can be either

• immediate open repair
  • further imaging is not required
  • speed may save life
• imaging with computed tomography followed by endovascular aneurysm repair if anatomically possible or open repair if no
  • less invasive and can be done under local anaesthesia in most, avoids life threatening severe hypotension associated with general anaesthesia in a bleeding patient (3).

Reference:

• (1) Moll FL et al. Management of abdominal aortic aneurysms clinical practice guidelines of the European society for vascular surgery. Eur J Vasc Endovasc Surg. 2011;41 Suppl 1:S1-S58.
• (2) Keisler B, Carter C. Abdominal aortic aneurysm. Am Fam Physician. 2015;91(8):538-43.
• (3) Björck M.Surgery for ruptured abdominal aortic aneurysm. BMJ. 2014;348:g95