The UK NHS AAA screening programme was started in 2009. Screening is carried out according to the pathway described in Figure 1. Considering medical practice and diagnostic criteria in Europe, it is likely that the screening pathway would be similar in other European countries if AAA screening were implemented.

Figure 1. Abdominal aortic aneurysm screening pathway in UK {1}

NHS guidelines for AAA screening {2} have identified 65-year-old men as the target population for AAA screening based on clinical studies. In the UK all men who are registered with a general practitioner (GP) will receive a personal invitation by mail for screening in the year that they turn 65. Men older than 65 can self-refer into the programme. Invitations are sent and feedback collected by local screening centres. Men who do not attend their screening invitation are either sent a second appointment or asked to contact their local programme to arrange a new date. Men who are invited a second time are sent a further letter saying they will not be invited for further appointments but can contact their local screening programme to self-refer for screening {2}.

Clinic locations are decided locally to ensure that they are accessible. Scanning typically takes place within community healthcare facilities such as community clinics, community hospitals, mobile units and primary care facilities. Men are seen by a health professional (sonographer or screening technician) on arrival at the clinic so that they can receive further information about screening before deciding whether to participate. Men are asked to give their consent to the screening procedure and the use of their personal information. Screeners record two anteroposterior (AP) measurements in centimetres of the maximum abdominal aortic diameter. Results are communicated immediately to all men verbally. Written results are also sent to GPs. Further investigations and treatment depend on the results of the scan:

• Normal result: the aorta has a diameter of less than 3 cm. No aneurysm has been detected. The man is informed of his result and does not require any further scans
• Small aneurysm: the aorta is slightly enlarged and has a diameter of between 3 and 5.4 cm. Men with a small aneurysm do not need to have treatment but are invited to have follow-up scans to monitor the size of the aneurysm.
• If the aorta is between 3 and 4.4cm a follow-up scan is offered in a year
• If the aorta is between 4.5 and 5.4cm a follow-up scan is offered in 3 months

In addition to follow-up scans, men are offered advice on how to reduce their cardiovascular risk factors. The man's GP may also be informed of the need to review medication and reassess blood pressure monitoring,

• Large aneurysm: the aorta has a diameter of over 5.5 cm. Men with a large aneurysm are referred to a consultant vascular surgeon to discuss treatment. Because of screening, surgeons need to be prepared for more elective surgery. A minimum of 20 operations per unit per year is defined as the quality standard. Alternative treatment is endovascular aneurysm repair (EVAR) {2}.

If the aorta cannot be visualised at the clinic a further scan appointment is arranged. If it cannot be visualised at the second appointment then the man is invited for a further scan at a hospital medical imaging unit. He is given guidance recommending minimum food and drink intake in the 4-h period before the proposed scan. Letters are also sent to GPs informing them of non-visualised screening results {2}.

The most significant impact of the screening programme will be on vascular surgery services and theatres. The number of elective operations will increase but there will be a decrease in the number of emergency operations over time {3}. A meta-analysis of four randomised controlled trials of screening older men for AAA was carried out by Lindholt and Norman (2008).  A significant reduction in emergency operations (odds ratio=0.55; 95% confidence interval (CI) 0.39-0.76) and an increase in elective operations (odds ratio=3.27; 95% CI 2.14-5.00) was found {4}.

As systematic population-based AAA screening has not been implemented in most European countries, the possible change after introducing the screening, can be estimated based on the number of elective and emergency operations at present. Mani et al. (2011) have analysed the statistics of AAA repair in several European countries. Table 1 shows the numbers of elective and emergency operations for Denmark, Norway and Sweden.

Table 1. Elective and emergency AAA operations in three European countries {5}

As a result of the increasing number of elective and the decreasing number of emergency operations after the introduction of AAA screening, the workload in involved hospital departments changes. According to The Scottish Government Health Improvement Strategy Division, patients who survive emergency repair of a ruptured AAA are admitted to the intensive treatment unit (ITU) and prolonged ITU admissions are common. After elective open AAA repair most patients in Scotland are admitted to the high dependency unit (HDU) rather than the ITU. After EVAR repair most patients are admitted to an HDU for one day but in some hospitals in Scotland patients are admitted to the vascular surgery ward after the procedure and do not occupy critical care beds {3}.

AAA screening is different from other screening programmes in that the mortality rates associated with treatment are significant: 3-5% for open surgery and 1-3% for EVAR {3}.

Therefore actual mortality is very dependent on the percentage of men that are treated with EVAR repairs. Also other risk factors like age and sex influence mortality. More detailed information about the percentage of EVAR procedures and the percentage of procedures done in women for Denmark, Norway and Sweden are presented in Table 2.

Table 2. Mean age, % of procedures in women and% of EVAR procedures for elective and emergency operations in three European countries (95% CI) {5}

The Vascular Society of Great Britain and Ireland has issued a framework for improving the results of elective AAA repair. The aim of the framework is to halve the mortality rate for elective AAA surgery in the UK (to 3.5%) by 2014 {6}.

Preoperative:

• All patients should undergo standard preoperative assessment and risk scoring to determine their suitability for EVAR.
• Each hospital should have defined pathways for the correction of significant medical risks (cardiology/renal/respiratory) before intervention.
• All patients should be seen by an anaesthetist for reviewing and optimising medication.
• All elective procedures should be reviewed preoperatively by surgeon(s) and radiologist(s) as a team. Ideally, a vascular anaesthetist should also be involved to consider fitness issues that may affect whether open repair or EVAR is offered.

{6}.

Operation:

• Interventions should be undertaken (or supervised) by a consultant surgeon/radiologist/anaesthetist with training and expertise in elective vascular procedures and a routine clinical practice in this specialty.
• Open AAA repair should include the following components: normothermia, cell salvage, rapid infuser, easy access to blood products (within 1 hour) and availability of haemostatic agents including glue.
• EVAR should only be undertaken in a sterile environment of theatre standard, with optimal imaging facilities. A range of rescue stents and devices should be immediately available, together with the expertise to deploy them {6}.

Facilities:

Elective AAA repair should only be undertaken in hospitals where:

• There is a 24/7 on-site vascular on-call rota for vascular emergencies of 1:6 or greater, covered by consultant vascular surgeons and interventional radiologists, to ensure adequate post-operative care.
• There is a 24/7 critical care facility with the capacity to undertake mechanical ventilation and renal support, and with 24-hour on-site anaesthetic cover.
• Wards for dedicated vascular patients should be available with the provision for single sex cubicles or bays.
• At least one endovascular theatre or theatre specification interventional radiology suite is required, preferably with a fixed C arm and a dedicated X-ray table.
• A minimum number of AAA procedures are undertaken. It is recommended that hospitals undertaking fewer than 33 elective AAA interventions per year (100 over 3 years) should not continue to offer these procedures.
• Hospitals should know their AAA mortality and should seek to validate both national audit and Trust data. They should be able to demonstrate safe practice.
• Units with mortality rates for elective repair of 6% or greater should seek external professional review of their care processes.
• An on-site vascular laboratory should be available {6}.

Also the Scottish AAA screening programme foresees a minimum of 20 elective surgeries per unit per year, rising over time to an estimated 32. Patients found to have an AAA should be referred to services that can undertake both open and endovascular repair of aneurysm and that offer advice to each patient on which procedure is most appropriate {3}. All referrals must be assessed for suitability for EVAR. It is estimated that 50% of screen-detected aneurysms in Scotland will be suitable for endovascular repair {3}.

There may be a small impact on Primary Care services from men requesting further information on the screening programme. Information on the screening programme will be circulated to Primary Care prior to roll out. GP practices will be notified of patients who are on surveillance or referred to vascular services {3}.

The difference in patients’ paths is that more men are referred for treatment before AAA rupture (which would send them directly to emergency departments).