A leaking or ruptured aneurysm is a medical emergency
Call for Emergency Help for Sudden Severe Pain, Faintness or Collapse
Seek immediate emergency care if you have:
- Sudden, severe or persistent abdominal, back, side or groin pain—especially with a known AAA.
- Fainting, collapse, severe dizziness, confusion or new extreme weakness.
- Pale, cold or clammy skin, a very rapid heartbeat or marked breathlessness with abdominal or back pain.
- A painful pulsating sensation or mass in the abdomen.
- New severe pain after recent aortic repair or another vascular procedure.
Do not drive yourself and do not wait for a booked scan. Emergency teams may perform an immediate bedside
ultrasound, but a scan that is unavailable or inconclusive must not delay vascular assessment when rupture is
still suspected.
What is an Abdominal Aortic Aneurysm?
The aorta is the body's largest artery. It travels from the heart through the chest and abdomen before dividing
into the iliac arteries that supply the pelvis and legs. An aneurysm is a permanent abnormal enlargement caused
by weakening and remodelling of the arterial wall.
In most screening and surveillance systems, an abdominal aorta measuring 3.0 cm or more is classified as an AAA.
Most occur below the kidney arteries and are called infrarenal aneurysms. Many cause no symptoms and are found by
screening or incidentally on imaging performed for another reason.
The Number Must Be Interpreted With the Measurement Method
Ultrasound programmes may measure outer wall to outer wall, inner wall to inner wall or by a leading-edge
method. The scan plane also matters in a curved aorta. Small differences between reports may reflect technique,
so growth should be judged with comparable measurements and the complete clinical record.
Screening, Surveillance and Emergency Assessment Are Different
Screening ultrasound
A one-time scan offered to selected people without symptoms because age, smoking or family history makes
an unsuspected AAA more likely.
Surveillance ultrasound
Planned repeat measurement of a known small or medium AAA. The interval depends on diameter, growth,
symptoms, local programme and the vascular specialist's plan.
Diagnostic ultrasound
Assessment requested because the aorta feels enlarged, an aneurysm was seen on another scan or abdominal
or back symptoms raise a stable clinical concern.
Emergency bedside ultrasound
Rapidly confirms whether an AAA is present in a person with suspected symptomatic or ruptured aneurysm.
It does not safely exclude active leaking when the aorta is poorly seen or no aneurysm is demonstrated.
Post-repair surveillance
A specialised protocol after open or endovascular repair. It may assess graft position, aneurysm-sac size
and endoleak and is not interchangeable with a basic screening scan.
Who May Be Offered AAA Screening?
Screening policy varies between countries and health systems. Many major guidelines strongly support one-time
ultrasound for men aged 65–75 who have ever smoked. Screening in people who have never smoked and in women is
individualised because the balance of benefit depends on age and risk.
Men aged 65–75 who have ever smoked
This is the best-established one-time screening group. “Ever smoked” includes former smoking; local
programmes may use their own definitions and invitation age.
Men in this age group who never smoked
Screening may be considered selectively using family history, cardiovascular disease and other risk
factors rather than being offered automatically in every system.
Women and younger or older adults
Routine population screening evidence is less certain, but an individual scan may be appropriate with
a first-degree relative, smoking history, vascular disease or a suspected aneurysm on examination.
First-degree family history
A parent, sibling or child with AAA increases risk. Discuss the appropriate age and timing with a clinician
rather than arranging repeated unsupervised scans.
These recommendations apply to people without symptoms. Sudden severe pain or collapse is an emergency regardless
of age, sex or whether the person would normally qualify for screening.
Why Might the Scan Be Requested?
One-time screening
To find a silent aneurysm in someone whose age and risk history justify screening.
Known AAA surveillance
To record the maximum diameter and determine whether the aneurysm has enlarged.
Pulsatile abdominal finding
To assess a widened or pulsating aorta felt during clinical examination.
Incidental enlargement
To confirm and measure an aortic abnormality seen on another ultrasound, CT or MRI.
Other reasons can include:
- Follow-up of an abdominal aorta described as ectatic or borderline enlarged.
- Assessment of the common iliac arteries when enlargement is suspected.
- A family history of AAA or another aortic aneurysm.
- Planning the next vascular review after a change in symptoms or diameter.
- Selected surveillance after aortic repair using a dedicated vascular protocol.
A routine complete abdominal ultrasound may mention the aorta but is not always equivalent to a dedicated,
documented AAA screening or surveillance examination.
What Raises the Risk of AAA?
Smoking
Current and previous tobacco exposure is the strongest modifiable risk factor and is associated with
development, enlargement and rupture.
Increasing age and male sex
AAA becomes more common with age and is more frequently diagnosed in men, although women can develop
aneurysms and must not ignore compatible emergency symptoms.
Family history
Having a first-degree relative with AAA raises risk and may influence whether and when screening is offered.
Cardiovascular disease
Coronary, carotid or peripheral arterial disease, high blood pressure and other vascular risk factors
commonly occur in the same people, although they do not predict an aneurysm on their own.
Having one risk factor does not mean an aneurysm is present, and having no obvious risk factor does not make
sudden severe symptoms safe to ignore.
How is This Different From Other Aortic Tests?
Dedicated aortic ultrasound
Measures the abdominal aorta and often the common iliac arteries without radiation or contrast. It is
the preferred test for screening and routine surveillance when views are adequate.
Complete abdominal ultrasound
Evaluates the liver, gallbladder, kidneys, spleen and other upper-abdominal structures. The aorta may be
checked, but detailed aneurysm measurements are not automatically the study's main purpose.
CT angiography / CTA
Maps the aneurysm, branch vessels, iliac arteries and access route in three dimensions. It is central to
repair planning and suspected complications but uses radiation and usually iodinated contrast.
MR angiography / MRA
Provides cross-sectional vascular imaging without ionising radiation. It is useful in selected patients
but takes longer and may involve contrast and implant-safety considerations.
Echocardiography
Assesses the heart, valves and visible portions of the aortic root and thoracic aorta. It does not replace
a dedicated transabdominal scan of the infrarenal aorta.
What Does the Radiologist Assess?
Proximal, middle and distal abdominal aorta
The vessel is followed from the diaphragm towards its division into the iliac arteries, as far as bowel
gas and body habitus allow.
Maximum anteroposterior diameter
The front-to-back diameter is measured perpendicular to the vessel's long axis at the widest point. A
transverse measurement may also be recorded.
Level and extent
The report states whether enlargement is below, at or above the kidney arteries when this can be determined
and whether it reaches the aortic bifurcation or iliac arteries.
Shape
Fusiform describes circumferential enlargement; saccular describes a localised outpouching. Saccular or
otherwise atypical findings often require vascular review and cross-sectional imaging.
Mural thrombus and lumen
Clot commonly lines part of an aneurysm. The outer wall—not only the flowing central channel—must be
included when measuring overall aneurysm size.
Common iliac arteries
Their diameters and visible patency are assessed when the requested protocol and views allow because
aneurysmal enlargement can extend beyond the aortic bifurcation.
Doppler flow
Colour and spectral Doppler may confirm patency and flow direction. A basic screening scan does not use
Doppler appearance to determine rupture risk.
Comparison with prior measurements
The maximum diameter is compared with earlier studies using attention to technique. A meaningful trend
is more important than an isolated small difference.
How Are Size and Follow-Up Described?
The maximum diameter is central to follow-up, but symptoms, growth, shape, sex, overall health and suitability
for repair also matter. The categories below are widely used in screening programmes; your local vascular team
may use a different interval or measurement convention.
Less than 3.0 cm
Usually reported as no AAA on a screening examination. Some aortas below 3.0 cm are described as ectatic
or mildly enlarged and may receive an individual follow-up recommendation.
3.0–4.4 cm: small AAA
Commonly monitored rather than repaired. Some national programmes use annual ultrasound, but the written
plan from the treating service takes priority.
4.5–5.4 cm: medium AAA
Requires closer vascular surveillance. Some programmes scan every three months; local protocols and
individual growth determine the actual interval.
5.5 cm or more: large AAA
Usually prompts timely specialist assessment for possible repair. It does not mean rupture is occurring,
and the decision is not based on diameter alone.
Rapid growth or new symptoms
Enlargement faster than expected or pain attributable to the aneurysm can trigger earlier vascular review
even below a usual size threshold.
Do not calculate your own next scan from an internet table. Follow the interval documented by the vascular team,
and seek urgent care for new severe abdominal or back pain regardless of the last recorded size.
How Should I Prepare?
Bowel gas can obscure the aorta, so many departments ask patients not to eat for about six hours. Instructions
vary; use the preparation supplied with your appointment rather than fasting unnecessarily.
Food and drink
If asked to fast, avoid solid food for the stated period. Small amounts of clear water are commonly allowed,
including for essential tablets, unless your booking instructions say otherwise.
Medicines and diabetes
Continue regular medicines unless instructed otherwise. If you use diabetes treatment, ask
for a safe fasting plan and an early appointment rather than adjusting treatment yourself.
Smoking, chewing gum and fizzy drinks
Avoid these during the fasting period when advised because swallowed air can make the aorta harder to see.
Previous imaging
Bring earlier ultrasound, CT, MRI and vascular-clinic reports. The exact date, diameter and measurement
method are important when growth is being assessed.
- Wear loose two-piece clothing so the abdomen can be exposed from the lower ribs to the pelvis.
- Mention previous aortic or abdominal surgery, stent-graft repair and any known iliac aneurysm.
- Tell the team about new abdominal, back, flank or groin pain before the routine scan begins.
- No full bladder is usually required for a dedicated AAA scan.
- Fasting should never delay emergency assessment for possible rupture.
What Happens During the Scan?
1
The reason and previous diameter are confirmed
The radiologist checks whether this is first screening, planned surveillance, an incidental finding or
post-repair imaging and asks about any new pain.
2
You lie on your back
The abdomen is exposed from beneath the breastbone to below the navel. You may later turn slightly onto
one side to improve the view.
3
The aorta is followed in two planes
Gel is applied and the probe traces the vessel in long-axis and transverse views from the upper abdomen
to its division into the iliac arteries.
4
Gentle pressure moves bowel gas
Firm but controlled probe pressure and breath-holding may improve the image. Tell the radiologist if
pressure is painful.
5
The maximum diameter is measured
Measurements are made at the widest section and at other standard levels. Any thrombus, unusual shape or
iliac enlargement is documented, with Doppler when required.
6
The surveillance or referral pathway is recorded
The report states whether there is no aneurysm, an ectatic aorta or an AAA and whether vascular review,
repeat ultrasound or CTA is recommended.
The scan commonly takes 15–25 minutes. Extra time may be needed when bowel gas obscures the vessel, the aorta is
tortuous or a dedicated post-repair Doppler protocol has been requested.
What Do Common Report Terms Mean?
No abdominal aortic aneurysm
The measured abdominal aorta is below the diagnostic threshold and the visualised segments show no AAA.
The report should state if any important segment was not seen.
Ectatic aorta
The aorta is mildly enlarged but does not meet the service's AAA definition. Recommendations vary with
diameter, age and local protocol.
Infrarenal AAA
The aneurysm lies below the arteries supplying the kidneys—the most common location.
Juxtarenal or suprarenal aneurysm
Enlargement reaches the level of or extends above the renal arteries. CTA or MRA is usually needed to
map branch-vessel involvement accurately.
Fusiform / saccular
Fusiform means the vessel expands around its circumference; saccular means a localised pouch. Shape helps
determine the appropriate next investigation and specialist review.
Mural thrombus
Clot lines part of the aneurysm wall. It is included within the total outer aneurysm diameter and does
not guarantee protection from further enlargement or rupture.
Tortuous aorta
The vessel follows a curved course. Measurements should be taken perpendicular to its axis rather than
across an oblique slice that can exaggerate size.
Common iliac artery aneurysm
One or both pelvic arteries are enlarged. The vascular team considers their diameter and anatomy separately
from the abdominal aortic measurement.
Technically limited / obscured by bowel gas
Part of the aorta could not be measured confidently. Repeat ultrasound or CT/MR imaging may be needed
when the clinical question remains important.
Interval growth
The aneurysm measures larger than on a previous study. The team considers elapsed time, measurement method
and scan quality before deciding whether growth is clinically significant.
What Can Ultrasound Not Determine Reliably?
- Whether an aneurysm is actively leaking or has ruptured solely from a stable outpatient scan.
- The exact risk of future rupture from diameter alone.
- The complete repair anatomy, including branch vessels, neck angulation and access arteries, without CTA or MRA.
- Every aortic segment when bowel gas, obesity, abdominal wounds or calcification blocks the ultrasound beam.
- The thoracic aorta within the chest or the full extent of an aneurysm that continues above the diaphragm.
- That mural thrombus makes the aneurysm stable or prevents rupture.
- A true growth trend when studies use different planes, calliper conventions or imaging modalities.
- All endoleaks or other complications after endovascular repair without a dedicated surveillance protocol.
Ultrasound is excellent for detection and serial diameter measurement when views are adequate. CTA is usually
required for repair planning, suspected complication or anatomy that is not fully demonstrated.
What Happens After the Scan?
You can wipe away the gel and resume normal food, medicines and activity. The report documents the maximum aortic
diameter, location, visible iliac measurements, technical limitations and comparison with previous imaging.
No AAA
Further routine screening may not be required after a satisfactory one-time screen, depending on age,
diameter and programme policy.
Small or medium AAA
Usually enters a vascular surveillance programme. Stopping smoking, controlling blood pressure and
cholesterol and managing overall cardiovascular risk are important; no medicine reliably shrinks an AAA.
Large, rapidly enlarging or symptomatic AAA
Requires timely vascular assessment. CTA commonly maps anatomy before a decision about open or endovascular
repair, with individual risks and benefits discussed by the specialist team.
Limited scan
The report may recommend another ultrasound or CT/MR imaging rather than treating the unseen segment as normal.
Keep every surveillance appointment even when you feel well. If sudden severe abdominal or back pain, faintness
or collapse occurs, seek emergency care and tell the team that you have a known AAA.
Myth vs Fact
Myth
An aneurysm always causes symptoms.
Fact
Most AAAs found by screening are silent. That is why selected higher-risk people are offered a one-time
ultrasound before symptoms develop.
Myth
Feeling a pulse in the abdomen proves there is an AAA.
Fact
A normal aorta can be easy to feel in a thin person, and abdominal structures can transmit pulsation.
Ultrasound determines the actual vessel diameter.
Myth
A routine scan can always show whether the aneurysm is leaking.
Fact
Ultrasound reliably confirms that an AAA exists but may not demonstrate retroperitoneal bleeding.
Symptoms and urgent vascular assessment remain decisive.
Myth
Clot inside the aneurysm makes it safe.
Fact
Mural thrombus is common and is included in the overall diameter. It does not remove the need for
surveillance or specialist management.
Myth
Every AAA needs immediate surgery.
Fact
Many small aneurysms are monitored safely. Repair is considered when size, growth, symptoms, shape
and the person's overall health make its benefit outweigh the procedural risk.
Frequently Asked Questions
Is an AAA scan the same as a full abdominal ultrasound?
No. A dedicated AAA scan concentrates on aortic diameter and often the common iliac arteries. A complete
abdominal scan evaluates multiple organs and may not include the same vascular documentation.
Do I need to fast?
Many departments request no food for about six hours to reduce bowel gas, while some screening programmes
require little or no preparation. Follow the instructions supplied for your specific appointment.
Will the scan hurt?
It is usually painless. The radiologist may press firmly to move bowel gas. Say immediately if you have pain,
particularly new severe abdominal or back pain.
Is an aorta below 3 cm always completely normal?
It does not meet the usual AAA definition. A mildly enlarged or ectatic aorta may still be described, and
follow-up depends on the exact diameter, age and local policy.
Why is my ultrasound measurement different from CT?
The body position, vessel plane, calliper placement and CT centreline method differ. Small discrepancies are
common; specialists compare the images and methods rather than subtracting report numbers in isolation.
Can ultrasound tell when an AAA will rupture?
No. Diameter and growth help estimate risk, but no scan predicts the exact time. New pain or collapse requires
emergency care regardless of a recent reassuring surveillance visit.
Can women develop an AAA?
Yes. AAAs are less common in women, so routine population screening policy differs, but family history,
smoking and clinical findings can justify individual assessment. Emergency symptoms must not be dismissed.
Can exercise make a small AAA burst?
Normal activity is not automatically prohibited. The vascular team may tailor advice to aneurysm size, blood
pressure, other heart disease and exercise intensity. Do not start or stop strenuous activity solely from a web page.
Will I need an operation if an aneurysm is found?
Not necessarily. Small and medium aneurysms are commonly monitored. A vascular specialist considers repair
for a large, rapidly enlarging, symptomatic or otherwise concerning aneurysm and discusses open and endovascular options.
When will I receive the result?
The radiologist prepares a report for the referring clinician. Significant or urgent findings are communicated
through the appropriate pathway. Ask how and when the diameter and follow-up plan will be discussed.