How are aneurysms diagnosed and investigated?
What symptoms do aortic aneurysms cause?
Most aortic aneurysms cause no symptoms, so the only way that you may know you have one is by feeling pulsation in your abdomen (although that may be normal if you are slim). Some patients may say that they have felt a ‘heartbeat’ in the midpart of their abdomen.
A few aneurysms cause discomfort, especially if they are large and place pressure on surrounding structures. This usually takes the form of constant, nagging pain, which may be felt in the back and/or abdomen.
Aneurysms do not usually cause pain on movement, twinges of pain or colic: those kinds of pain are likely to result from other conditions, such as spinal problems or colonic spasm (irritable bowel).
If an aortic aneurysm starts to leak then acute symptoms occur, which are described in the section ‘Ruptured leaking aortic aneurysms’.
How easy is it to feel an aortic aneurysm?
The aorta lies right at the back of the abdomen, to the front of the spine, so it can enlarge a lot without being noticeable, even during a medical examination of the abdomen.
In slim people it can be easy to feel the normal abdominal aorta, and to see its pulsation in the middle of the abdomen, particularly after exertion or when a person is anxious (when the heart is beating hard and fast).
Aneurysms in slim people may therefore be very obvious. In people who are obese or stocky, the aorta may be impossible to feel, even if there is a big aortic aneurysm.
When medical examination of a patient’s abdomen raises suspicion that an aortic aneurysm may be present, it is often difficult to be certain, and impossible to be sure about its exact size. A scan is always necessary to discover the exact width of the aorta.
How are aortic aneurysms found?
Abdominal X-ray
Some aneurysms are discovered by chance on X-rays done for other reasons – for example, X-rays of the lumbar spine for low back pain or X-rays of various kinds done during investigation of abdominal pain.
An aortic aneurysm shows up because its wall often contains a thin layer of calcium which can be seen on an X-ray. Further scans are needed to show the aneurysm in more detail.
Ultrasound scanning
An ultrasound scan (the same type of scan that a woman will have during pregnancy) is the usual way of diagnosing a suspected aortic aneurysm and it is the test used in routine screening for aneurysms (see section ‘Screening for abdominal aortic aneurysms’).
Ultrasound jelly is applied to the abdomen to ensure a good contact for the probe. The probe is smooth and moved over the skin surface to provide a picture of the underlying tissues on a monitor screen. The width of the aorta is measured (this is the most important part of the examination) and the extent of the aneurysm can often be seen.
Ultrasound scanning of the aorta is usually quick and straightforward, but sometimes it can be difficult. It depends on the experience of the person doing the examination but even an expert may not be able to get an adequate view of the aorta if there is a lot of gas in the bowel or in an obese abdomen. In particular, it may be impossible to see exactly how high an aneurysm extends.
Measurement of the width of an aneurysm by ultrasound has a possible error of about 2 to 3 mm (for example a measurement of 5.0 cm might mean a true width from about 4.8 cm to 5.2 cm). Ultrasound can sometimes overestimate the width of an abdominal aortic aneurysm if the measurement is done obliquely rather than straight across. Despite these possible inaccuracies, ultrasound is generally the best way of seeing if an aneurysm is present and giving a good indication of its size.
Computed tomography and magnetic resonance imaging
These are both computerised forms of scanning which show up the tissues and the blood vessels in great detail. Computed tomography (CT) scans are the most usual for detailed investigation of aortic aneurysms. They show the precise size and shape of any aneurysm and also show exactly how far it extends. These details are important in advising on the possibilities for treatment, particularly whether an aneurysm is suitable for a stent graft (EVAR).
Both CT and MRI involve a few minutes lying inside a scanner, and MR scans are noisy. Some people who are claustrophobic therefore find these kinds of scans disturbing.
Arteriography (or angiography)
Pictures of the arteries are taken after contrast (‘dye’) has been injected to show them up on X-rays. Arteriography using X-rays is seldom needed for investigation of aortic aneurysms, but it is sometimes used if there are concerns about other arteries, in addition to the aorta. Arteriography is used as part of the procedure of EVAR (stent grafting) of aneurysms (see section ‘Endovascular aneurysm repair’).
Good pictures of the inside of the arteries can now be provided by CT (after injection of contrast) or MRI (without injection of contrast).
