Abdominal Aortic Aneurysm ========================= See Also: (other) Aneurysms Infected Aneurysms Portal Vein Thrombosis Aortic Dissection þ Dissection: - 7/8 will NOT have a pulse or BP deficit - 33% normotensive - tearing pain to chest, abdomen, back: 1/6 won't have this - only 5% present with solely abdominal pain (usually pressurelike) - abrupt onset common, but 84 hour usual time to diagnosis - migratory pain a sign of dissection? Pain fron chest, to arm, back, abdomen; found only in minority - may develop stroke symptoms - widening of mediastinum: only in 50% for Type B dissection (21% read as normal by radiologist) þ Clinical Features - diaphoresis considered an important sign by surgeons - AAA tends to rupture down and left, mimicking diverticulitis þ Pathogenesis - not just a complication of atherosclerosis - risks include family history, genetic predisposition, acquired biochemical changes in matrix of aortic wall, hemodynamics {NEJM 1993;328(16):1167-72.} þ Natural History: - annual expansion rate is 0.3 to 0.57 cm - large (5-6 cm) aneurysms expand more rapidly than small ones. [NEJM 1989;321:1009-14.] - Rapid diagnosis in ED decreases mortality, decreases from 2/3 to 1/3 of them dying - 30% misdiagnosed early - dissection diagnosis time: 84 hours. - less than half of AAAs present with classic triad of hypotension, back pain and pulsatile mass - Exams of those with known >5cm aneurisym: 53% sensitive in fat patients [Lederle JAMA 1999] þ AAA Rupture Diagnosis - Unstable + Unstable patient with suspected ruptured AAA, or known AAA with classic triad of hypotension, back pain, loss of leg pulses (classic triad only in less than half with ruptured AAA): no tests, go directly to OR [Arch Surg 1988;123:1213-7.] + bedside ultrasound may be useful, but don't send off for CT, MRI, US. - stable + if stable enough to leave ED, CT is superior to ultrasound + just need to give oral contrast, and give it for a few minutes to get it starting through the duodenum. - ultrasound is nearly 100% for aneurysms, but not good at all to look for rutpures; MRI not as good as CT, either. [AJR 1994;163:17-29.] þ Differential Diagnosis - cholecystitis, diverticulitis, ischemic bowel, aortic dissection, lymphoma, adrenal hemorrhage, rectus sheath hematoma. [S Afr Med J 1988;74:165-7. J Vasc Surg 1990;12:28-33. Surg Gynecol Obstet 1986; 162:453-56. Surg Gynecol Obstet 1986; 162:49-53.] - misdiagonses of ruptured AAA: kidney stone, diverticulitis, GI hemorrhage, AMI, back pain, traumatic injury, sepsis (correct diagnosis made on CT) [J Vasc Surg 1992;16:17-22.] þ British study: - if have symptoms, and CT negative for blood, but crescent sign (calcium pulled away a little from the wall of the aorta, known to signify incipient rupture in radiology literature) admit for elective surgery. [BMJ 1988;297:284-5.]