Computed tomography in the determination of surgical emergency for symptomatic abdominal aortic aneurysm

What is the best surgical timing for symptomatic AAA? Surely, the answer depends on accurate and prompt diagnosis of 'rupture or not'. Abdominal CT is one of the reliable and familiar diagnostic tools. We will present our own CT classification method for symptomatic AAA which is used as the guideline for 'emergency or not'.

From January 1989 to January 1995, 52 patients with symptomatic AAA received diagnostic CT scan for quick disease differentiation and determination of surgical emergency. The findings were classified into four categories. Category I included 26 patients with intact aorta; Category II included four patients with contained retroperitoneal abdominal aortic leakage; Category III included 14 patients with contained massive retroperitoneal hematoma; and Category IV included eight patients with retroperitoneal or intraperitoneal active bleeding.

Compared with the standard diagnosis of rupture via laparotomy, CT is an excellent tool, showing 88% sensitivity and 88% specificity. This is better than sonography, which has a high false-positive rate of 33% and low specificity of 62%. Hospital mortality was distinctive with 4.3% in Category I, none in Category II, 25% in Category III and 87.5% in Category IV.

In our experience, CT scan is a better diagnostic tool than sonography for symptomatic AAA. Even the delay imposed by obtaining a preoperative CT scan in patients with possible ruptured aneurysm does not adversely affect the patient's outcome. The information obtained significantly aids not only preoperative but also intraoperative management.