Page 154 - Libro vascular I

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Chapter 11
Duplex assessment of aneurysms
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CHAPTER CONTENTS
Introduction 145
Definition of an aneurysm 145
Anatomy of the abdominal aorta 146
Pathology of aneurysms 146
Aortic aneurysms: symptoms and treatment 146
Surgical techniques for aortic aneurysm repair 147
Aneurysm shapes and types 149
Practical considerations for duplex scanning of
aortic aneurysms 149 Scanning technique 150 Ultrasound appearance 150
Normal appearance 150
Abnormal appearance 151
Measurements 152
Aorta diameter 152
Distance between the renal arteries and the
upper limit of the aneurysm 154
Limitations and pitfalls of aortic aneurysm scanning 154
Surveillance of endovascular aneurysm repair 154
Scanning technique 154
Types of endoleak 156
Assessment of aneurysms excluded by covered
stents 157
Other true aneurysms 157
Iliac aneurysms 157
Popliteal aneurysms 157 Femoral artery aneurysms 158
False aneurysms 158
Scanning false femoral aneurysms 159
Treatment of false femoral aneurysms 160
Reporting 160
INTRODUCTION
True aneurysms are abnormal dilations of arteries. The term ectasia is often used to describe a moder- ate dilation of arteries. The abdominal aorta is one of the commonest sites for aneurysms to occur. Rupture of abdominal aortic aneurysm (AAA) is a common cause of death in men over the age of 65 years. Ultrasound is a simple noninvasive method of detecting aneurysms and can be used for serial investigations to monitor any increase in size. However, if surgical intervention is being consid- ered, other imaging techniques, such as CT and MRI, may be required to demonstrate the relation- ship of an aneurysm to major branches and other structures within the body. There have been signif- icant developments in the treatment of aneurysms over the last several years, with the introduction of endovascular devices to repair aortic aneurysms and covered stents to exclude flow in aneurysms in other areas of the body. This chapter concentrates on ultrasound scanning of aortic aneurysms but also considers the assessment of aneurysms in other areas of the peripheral circulation.
DEFINITION OF AN ANEURYSM
It has been suggested that an aneurysm is a perma- nent localized dilation of an artery having at least a 50% increase in diameter compared to the normal, expected diameter (Johnston et al 1991). Ectasia is characterized by a diameter increase 50% of the normal, expected diameter. It is worth remembering that there is considerable variability in the normal diameter of arteries among individuals, and this will