A 74-year-old ex-smoker with a history of hypertension and hyperlipidaemia underwent open surgical repair of an infrarenal abdominal aortic aneurysm. The aneurysm had been under surveillance for 18 months, during which time it expanded from 4.8 cm to 6.2 cm on duplex ultrasonography. The structure marked **A** in the gross specimen represents the fusiform dilatation of the infrarenal aorta. Which of the following best explains why surgical intervention was indicated at this particular point in time?
A. The aneurysm had demonstrated rapid expansion of >1 cm over 18 months, indicating accelerated growth
B. The patient developed symptomatic claudication secondary to iliac artery involvement
C. The aneurysm diameter exceeded 5.5 cm, at which the annual rupture risk of approximately 10% outweighs perioperative mortality risk
D. The aneurysm had become symptomatic with acute-onset flank pain and haemodynamic instability
Explanation
Why option 1 is correct
The clinical anchor is the 5.5 cm threshold for infrarenal AAA repair. When the aneurysm marked A expanded to 6.2 cm, it exceeded this critical diameter at which the natural history risk of rupture (approximately 10% per year) becomes greater than the perioperative mortality risk of elective open repair. This size-based criterion is the standard indication for intervention in asymptomatic AAA and was the decisive factor in this patient's surgical timing. Per Sabiston Textbook of Surgery, 21st Edition, the 5.5 cm threshold represents the evidence-based cutoff derived from the UK Small Aneurysm Trial and ADAM trial, above which surveillance is no longer safe and repair is recommended.
Why each distractor is wrong
Option 2: While the aneurysm did expand by 1.4 cm over 18 months, rapid growth alone is not the primary indication for repair in this case. The patient was asymptomatic and the expansion rate, though notable, was not the determining factor—the absolute diameter crossing 5.5 cm was. Rapid expansion becomes relevant only if it occurs in aneurysms already close to threshold or in symptomatic patients.
Option 3: The patient had no claudication symptoms. Although bilateral common iliac involvement was noted on preoperative CT (28 and 26 mm), these measurements were below aneurysmal threshold and were not symptomatic. Iliac artery involvement alone does not mandate repair unless it causes symptoms or meets size criteria independently.
Option 4: The patient explicitly had not experienced any abdominal, back, or flank pain. Symptomatic presentation (pain, haemodynamic instability) would indicate emergency repair for suspected rupture or contained rupture, but this patient presented electively after crossing the 5.5 cm diameter threshold on surveillance imaging.
High-YieldNEET PG
Infrarenal AAA >5.5 cm diameter = elective repair indicated; rupture risk ~10%/year outweighs perioperative risk. Size, not symptoms, drives the decision in asymptomatic AAA.
Sabiston Textbook of Surgery, 21st Edition, Chapter on Aneurysmal Vascular Disease
Practice similar questions
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.
