Achieving good-quality consent: review of literature, case law and guidance.

BACKGROUND: Informed consent is an integral part of clinical practice. There is widespread agreement amongst health professionals that obtaining procedural consent needs to move away from a unidirectional transfer of information to a process of supporting patients in making informed, self-determined decisions. This review aimed to identify processes and measures that warrant consideration when engaging in consent-based discussions with competent patients undergoing elective procedures. METHODS: Formal written guidance from the General Medical Council and Royal College of Surgeons of England, in addition to peer-reviewed literature and case law, was considered in the formulation of this review. RESULTS: A framework for obtaining consent is presented that is informed by the key tenets of shared decision-making (SDM), a model that advocates the contribution of both the clinician and patient to the decision-making process through emphasis on patient participation, analysis of empirical evidence, and effective information exchange. Moreover, areas of contention are highlighted in which further guidance and research are necessary for improved enhancement of the consent process. CONCLUSION: This SDM-centric framework provides structure, detail and suggestions for achieving meaningful consent.

ANTECEDENTES: El consentimiento informado es una parte integral de la práctica clínica. Existe un acuerdo generalizado entre los profesionales de la salud en que lograr el consentimiento del procedimiento no debe ser una transferencia unidireccional de información, sino un proceso de apoyo a los pacientes en la toma de decisiones informadas y autodeterminadas. Esta revisión tiene como objetivo identificar procesos y medidas que deban ser considerados al hablar sobre el consentimiento con pacientes autosuficientes sometidos a procedimientos quirúrgicos electivos. MÉTODOS: Al planear esta revisión se tuvo en cuenta la recomendación formal por escrito del Consejo Médico General y del Royal College of Surgeons of England, además de la literatura revisada por pares y de la jurisprudencia. RESULTADOS: Se presenta un marco para lograr el consentimiento que se basa en los principios clave de la toma de decisiones compartida (Shared Decision-Making, SDM); un modelo que aboga por la contribución, tanto del médico como del paciente, al proceso de toma de decisiones a través del énfasis en la participación del paciente, el análisis de la evidencia empírica y el intercambio efectivo de información. Además, se destacan áreas de contención en las que se necesitan más recomendaciones y más investigación para mejorar aún más el proceso del consentimiento. CONCLUSIÓN: Este marco centrado en la SDM proporciona estructura, detalles y sugerencias sobre cómo se puede lograr un consentimiento informado satisfactorio.

The role of anatomy demonstrators: A surgical trainees' perspective.

Core Surgical Trainees (CST) in the London (UK) Postgraduate School of Surgery receive clinical anatomy teaching in their first year of training, and, in their second year, give 30 sessions of anatomy teaching to medical and other students. This study set out to investigate the role of demonstrators from the perspective of the trainees. A focus group was convened to ascertain trainees' perspectives on demonstrating anatomy and to identify problems and improvement strategies to optimize their ability to enhance students' learning. A questionnaire was formulated and all second-year CST (n = 186-from two cohorts) in the London Postgraduate School of Surgery were invited. A total of 109 out of 186 trainees completed the questionnaire. A high percentage (98%) of trainees that completed the questionnaire responded that demonstrating was an invaluable part of their training. Sixty-two per cent responded that anatomy teaching they received in their first year of core surgical training helped them in their teaching role and 80% responded that it helped them prepare for surgical training. The study also revealed the need for improved communication between trainees and the London Postgraduate School of Surgery/Medical Schools/National Health Service Trusts to address issues such as trainees' perceived difficulty in fulfilling their teaching session requirement. The stakeholders have acknowledged and addressed the outcomes to improve the experience for both surgical trainees and students. The results indicate that anatomy demonstrating delivers important benefits to early surgical trainees, in addition to those received by the students that they teach. Clin. Anat. 31:409-416, 2018. © 2017 Wiley Periodicals, Inc.

Risk factors associated with increased prevalence of abdominal aortic aneurysm in women.

BACKGROUND: Four randomized trials of men aged 65-80 years showed that aneurysm-related mortality was reduced by 40 per cent by ultrasound screening. Screening is considered economically viable when the prevalence of abdominal aortic aneurysm (AAA) is 1·0 per cent or higher. This is not the case for women, in whom the prevalence of AAA is less than 1 per cent. The aim of the present investigation was to determine the prevalence of AAA 3·0 cm or larger in women screened with ultrasound imaging, the risk factors associated with AAA in this population, and whether high-risk groups can be identified with an AAA prevalence of 1 per cent or greater. METHODS: Demographic data and risk factors were collected from the first 50 000 women who attended for private cardiovascular screening in the UK. Tests included ultrasound screening for AAA, ankle : brachial pressure index (ABPI), carotid duplex imaging for carotid atherosclerosis, and electrocardiography for atrial fibrillation. RESULTS: AAA was detected in 82 of 50 000 women screened; these aneurysms were rare below the age of 66 years (7 of 24 499). In the 66-85-years age group there were 72 AAAs in 25 170 women (0·29 per cent). Univariable analysis demonstrated that a history of stroke/transient ischaemic attack (TIA), hypertension, smoking, atrial fibrillation, ABPI of less than 0·9 and internal carotid artery stenosis of at least 50 per cent were associated with an increased prevalence of AAA (P < 0·001). In multivariable linear logistic regression of risk factors, age 76 years or more, history of stroke/TIA, hypertension and smoking were independent predictors of AAA. This model had an area under the receiver operating characteristic (ROC) curve (AUC) of 0·711 (95 per cent c.i. 0·649 to 0·772) and could identify 2235 women who had 22 AAAs (prevalence 0·98 per cent). By adding ABPI, atrial fibrillation and carotid stenosis, the prediction improved to an AUC of 0·775 (0·724 to 0·826). This model could identify 3701 women who had 58 AAAs (prevalence 1·57 per cent). CONCLUSION: This report should stimulate consideration of a targeted AAA screening programme for women aged over 65 years.

Variation in duplex peak systolic velocity measurement in a multi-site vascular service.

OBJECTIVE: Duplex US (DUS) is increasingly utilised as a first-line investigation for the assessment of carotid disease. For clinical decision-making, DUS assessment must be accurate and reproducible to ensure reliability. We aimed to investigate the variability in peak systolic velocity (PSV) measurement in a multi-site vascular network. METHODS: DUS measurements of PSV were taken from continuous and pulsatile flow, generated by a high fidelity phantom, by 12 experienced vascular scientists across four hospitals. Participants were blinded to the actual PSV value (50 cm/s). RESULTS: We observed an average error of 13.2% (± 8.3) and 11.6% (± 7.5) in PSV measurements taken from pulsatile and continuous waveforms, respectively. Measurements of PSV using the pulsatile waveform demonstrated statistically significant variation across all hospitals; ((hospital/mean) A 43.9 cm/s, B 61.7 cm/s, C 57.4 cm/s, D 47.7 cm/s, p=0.001). Further analysis demonstrated statistically significant variation in 4 instrumentation-related factors when measuring from a pulsatile waveform (Doppler angle, angle of insonation, velocity range, scale range). CONCLUSION: We observed a significant level of error and variation in PSV measurements across four sites within our vascular network. Variation in instrumentation-related factors may be accountable for this. In light of the centralisation of vascular services, it is increasingly important to unify and implement scanning protocols in order to reduce error and inter-site variability.

Validation of a novel duplex ultrasound objective structured assessment of technical skills (DUOSATS) for arterial stenosis detection.

INTRODUCTION: Duplex ultrasound facilitates bedside diagnosis and hence timely patient care. Its uptake has been hampered by training and accreditation issues. We have developed an assessment tool for Duplex arterial stenosis measurement for both simulator and patient based training. METHODS: A novel assessment tool: duplex ultrasound assessment of technical skills was developed. A modified duplex ultrasound assessment of technical skills was used for simulator training. Novice, intermediate experience and expert users of duplex ultrasound were invited to participate. Participants viewed an instructional video and were allowed ample time to familiarize with the equipment. Participants' attempts were recorded and independently assessed by four experts using the modified duplex ultrasound assessment of technical skills. 'Global' assessment was also done on a four point Likert scale. Content, construct and concurrent validity as well as reliability were evaluated. RESULTS: Content and construct validity as well as reliability were demonstrated. The simulator had good satisfaction rating from participants: median 4; range 3-5. Receiver operator characteristic analysis has established a cut point of 22/ 34 and 25/ 40 were most appropriate for simulator and patient based assessment respectively. We have validated a novel assessment tool for duplex arterial stenosis detection. Further work is underway to establish transference validity of simulator training to improved skill in scanning patients. CONCLUSIONS: We have developed and validated duplex ultrasound assessment of technical skills for simulator training.

The role of simulation in developing surgical skills.

Surgical training has followed the master-apprentice model for centuries but is currently undergoing a paradigm shift. The traditional model is inefficient with no guarantee of case mix, quality, or quantity. There is a growing focus on competency-based medical education in response to restrictions on doctors' working hours and the traditional mantra of "see one, do one, teach one" is being increasingly questioned. The medical profession is subject to more scrutiny than ever before and is facing mounting financial, clinical, and political pressures. Simulation may be a means of addressing these challenges. It provides a way for trainees to practice technical tasks in a protected environment without putting patients at risk and helps to shorten the learning curve. The evidence for simulation-based training in orthopedic surgery using synthetic models, cadavers, and virtual reality simulators is constantly developing, though further work is needed to ensure the transfer of skills to the operating theatre.

Evaluation of rapid training in ultrasound guided tourniquet application skills.

Tourniquet application has been widely accepted to improve survival for major limb trauma. Colour duplex ultrasound (US) can be used as a non-invasive method of confirming cessation of arterial flow. Participants with no or limited experience of ultrasound were taught to apply the Combat Application Tourniquet with ultrasound guidance. Following this, participants were tested in effective tourniquet application: Blind and with ultrasound guidance. US guidance improved abolition of limb perfusion from 22 to 93 per cent in upper limb; from 25 to 100 per cent in lower limb (p=0.0027 and <0.0001). No significant difference was found in application time for the lower limb; less time was taken for application with US guidance in the upper limb 8.1 (7.1, 8.6) vs 4.5 s (4.0, 5.3; median (IQR)), p=0.002. Tourniquet ultrasound skills are rapidly acquired by novice operators. Accuracy improves with ultrasound guidance, this may have a role in improving survival.

The surgical management of 73 vascular malformations and preoperative predictive factors of major haemorrhage--a single centre experience.

OBJECTIVES: In our series of patients with congenital vascular malformations (CVMs) we investigate the preoperative factors for predicting major haemorrhage at surgery and propose an algorithm for their surgical management. DESIGN: This is a partly prospective case series of patients with severe symptoms/complications due to CVMs. MATERIALS AND METHODS: Data were collected on 73 consecutive procedures in 41 patients with CVMs from 1992 to 2006 at a large university hospital and the association of following factors with blood loss during the procedure were investigated: type of procedure, possibility of proximal tourniquet use, lesion flow characteristics, previous history of major haemorrhage with CVM surgery, platelet counts and length of hospital stay. RESULTS: Significantly higher blood loss was associated with debulking surgery (p=0.006) and with previous history of major haemorrhage during CVM surgery, (p=0.041). Blood loss was higher in lesions where proximal tourniquet application was not possible (p=0.093). High-flow lesions were not strongly associated with major blood loss (p=0.288). Major blood loss (>2l) occurred in 16 (20.8%) procedures performed on 11 (26.2%) patients, but this did not prolong hospital stay. CONCLUSION: Surgery can potentially improve morbidity/mortality in patients with life/limb-threatening complications or severe symptoms due to CVMs, providing they are managed in multidisciplinary specialised centres.

Impaired hyperaemic and rhythmic vasomotor response in type 1 diabetes mellitus patients: a predictor of early peripheral vascular disease.

OBJECTIVES: The smooth muscle of distal vascular networks exhibits periodical contraction and relaxation known as rhythmical vasomotion. The nature of microvascular vasomotion has been shown to correlate with severity of peripheral vascular disease. We present basal and post-ischaemic hyperaemic laser doppler flowmetry vasomotion in control and type 1 adult diabetic patients. DESIGN: Prospective case control study. METHODS: Laser Doppler flowmetry was used to measure vasomotion and hyperaemic responses in age and body mass index matched male subjects (25 type 1 Diabetes Mellitus and 13 controls), all with ankle/brachial pressure index (ABPI) >1.0 but <1.2. RESULTS: The frequency of resting vasomotion was raised in diabetics compared to controls 8 (5-9)min(-1) vs. 5 (4-6)min(-1) (median (range); p<0.0001). The post ischaemic hyperaemia response was significantly higher in the diabetic group compared to the controls 11 (7-12)min(-1) vs. 6 (5-7)min(-1) (median (range); p<0.05). Post ischaemic hyperaemic flux (expressed as percent increase from resting) was significantly lower in the diabetic group compared to controls (234+/-62 vs. 453+/-155%, p<0.01). The time to achieve peak post ischaemic response was also significantly increased in the diabetic group compared to control: 21.4+/-0.4 vs. 12.8+/-5.4sec (mean+/-SD, p<0.05). CONCLUSIONS: Vasomotion frequency and its change during hyperaemic insult is significantly different in Type 1 Diabetes Mellitus subjects compared to controls. The results are similar to patients with macrovascular atherosclerosis. Long term studies of these groups of patients will be required to determine the significance of these findings and whether these changes could be used as a non invasive screening test to predict peripheral early vascular disease in type 1 diabetic patients.

Peripheral arterial revascularization causing parallel increased activity of pro- and anti-inflammatory mediators.

AIM: The aim of this study was to investigate the interaction between the proinflammatory mediator interleukin (IL)-6 and anti-inflammatory mediator IL-10 in ischemia reperfusion injury following peripheral arterial revascularization. METHODS: Three groups of patients were recruited (group 1: femoral angiography alone [n=14]; group 2: radiologically successful ilio/femoral angioplasty [n=10]; and group 3: peripheral surgical bypass [n=11]). Peripheral venous blood obtained for all patients at pre-procedure and at 1 h and 24 h post-procedure. After centrifugation supernatant plasma was separated and analysed for proinflammatory cytokine IL-6 and anti-inflammatory cytokine IL-10 using enzyme linked immunosorbent assay (ELISA) technique. RESULTS: Levels of IL-6 at 1 and 24 h were significantly higher in group 3 (P<0.05 and P<0.01, respectively) and at 24 h in group 2 as compared to group 1 (P<0.05). Levels of IL-10 were significantly higher in group 3 at 24 h (P<0.05). In group 2 levels of IL-10 higher than group 1, but this did not reach statistical significance (P=0.07). CONCLUSIONS: Raised levels of IL-6 at 1 and 24 h in patients undergoing operative peripheral bypass suggest early and persistent proinflammatory activity, similarly patients with successful angioplasty also demonstrated similar persistent proinflammatory activity of IL-6 at 24 h. Raised levels of IL-10 at 24 h represents anti-inflammatory properties of IL-10 counter acting inflammatory response.

Pre-operative radial arterial diameter predicts early failure of arteriovenous fistula (AVF) for haemodialysis.

INTRODUCTION: Long term patency of arteriovenous fistula (AVF) is relevant to the management of end stage renal failure (ESRF) patients on haemodialysis (HD). We evaluated the role of routine radial arterial duplex for imaging radial artery before AVF formation to investigate the relationaship between radial artery internal diameter (ID) and AVF patency. METHODS: 21 patients with ESRF were examined by duplex sonography before AVF formation, 1 day, 1 week, 4 week and 12 weeks post AVF formation. For assessment of AVF patency, patients were divided into 2 groups. Group-1, 11 patients with radial artery ID <1.5mm and Group-2, 10 patients with radial artery ID >1.5mm. Measurement of radial artery blood inflow rate was calculated from mean blood flow velocity and vessel diameter. All AVFs were constructed on the forearm using autologous veins. RESULTS: In Group-1, 5 patients (45%) showed immediate thrombosis of AVF graft. All patients in group-2 had patent AVF at 12 weeks. Pre-AVF formation radial artery blood inflow rate between two groups was not significantly different (p=0.06). Radial artery blood inflow rate was consistently and significantly higher in group-2 at all later time points with p value of <0.01 (Mann Whitney test). CONCLUSION: There was a high failure rate of AVF with radial artery ID of <1.5mm. In the presence of small radial arteries primary access AVF in the upper arm should be considered.

Tumor embolization causing acute ischemia with sometimes fatal results. Case report and review of literature.

Peripheral arterial embolism arising from a malignant tumor is an infrequent manifestation of neoplastic disease and also a rare cause of acute arterial occlusion. A diagnosis of lower limb acute ischemia in young adults could be overlooked because the condition is quite uncommon in this age group. A case of lower extremities arterial embolization from metastatic lung cancer of germ cell origin is reported and the literature is reviewed.

Nerve tissue protein S-100 and neurone-specific enolase concentrations in cerebrospinal fluid and blood during carotid endarterectomy.

Nerve tissue protein S-100 and neurone-specific enolase levels in serum were studied in 10 patients before, during and for 2 days after elective carotid endarterectomy performed under general anaesthesia and using a Javid Shunt. In six patients, simultaneous cerebrospinal fluid samples were also obtained. Serum nerve tissue protein S-100 was normal throughout the operation, but in one patient with severe hypertension, levels increased to 1.38 microg. l-1 at 1 h postoperatively. Two patients showed an increase in cerebrospinal fluid nerve tissue protein S-100 during clamping: these patients also had neurological deficits at 6 months. Serum neurone-specific enolase increased from 5.8 to 9.3 microg.l-1 during shunting while cerebrospinal fluid neurone-specific enolase did not change. Uncomplicated carotid endarterectomy does not produce cerebral damage as measured by serum nerve tissue protein S-100; cerebrospinal fluid nerve tissue protein S-100 may be more sensitive for minor cerebral damage. Neurone-specific enolase appeared to be nonspecific. The lack of correlation between the neuroproteins may need to be explained before relying on these simple assays as diagnostic indicators of cerebral ischaemia.

Arterial flow induces changes in saphenous vein endothelium proteins transduced by cation channels.

OBJECTIVES: expression of leukocyte adhesins and proteins controlling thrombosis is likely to be an important determinant of graft patency early following vein bypass. We have previously demonstrated rapid increase in endothelial ICAM-1 and nitric oxide synthase (eNOS) concentrations in human saphenous vein exposed to arterial flow. The aim of this study was to investigate whether ion-channel-blocking drugs could alter these flow-induced changes. METHODS: human saphenous vein segments, freshly excised from patients, were placed in a validated in vitro circuit using flow conditions shown to simulate arterial or venous circulations for 90 min, in the presence or absence of ion-channel blockers. The concentrations of ICAM-1, VCAM-1, eNOS and tissue factor (TF) were assessed by quantitative immunohistochemistry in vein exposed to flow and compared with that in freshly excised vein from the same patient. The endothelial protein concentration was calculated as the mean area of staining as percentage of that for the control protein CD31, using computer-aided image analysis. RESULTS: after arterial flow conditions the area ratio of ICAM-1 increased from 21.4+/-1.4 to 44.6+/-2.0%, of eNOS increased from 50.0+/-5.6 to 70.1+/-5.0%, of VCAM-1 decreased from 16.6+/-3.4 to 3.6+/-1.0%, whereas TF staining area ratio was unchanged. Inclusion of the non-selective K(+)channel blocker, tetraethylammonium, in the arterial perfusion solution abolished all these arterial flow-induced changes. Inclusion of the K(+)ATP channel blocker, glibenclamide, selectively abolished the arterial flow-induced changes in ICAM-1 and VCAM-1. Inclusion of the calcium channel blocker, nifedipine, abolished the arterial flow-induced changes in eNOS and VCAM-1 but increased the TF staining area ratio from 3.0+/-0.4 to 8.5+/-0.7%, p=0.01. Inclusion of the stretch-activated cation-channel blocker, gadolinium, enhanced the arterial flow-induced increase in eNOS, but prevented the arterial flow-induced increase in ICAM-1. CONCLUSIONS: perfusion of veins under arterial flow conditions with gadolinium was associated with low endothelial concentrations of ICAM-1, VCAM-1 and TF, but high levels of eNOS. Such a concentration of endothelial proteins may be advantageous in newly implanted vein grafts. In contrast, nifedipine could have adverse effects by promoting increase in TF concentration.

Functional renal perfusion imaging with colour mapping: is it a useful adjunct to spiral CT of in the assessment of abdominal aortic aneurysm (AAA)?

AIM: To ensure optimal timing with pre-operative spiral CT for abdominal aortic aneurysms (AAA), an initial 'timing' single level CT is commonly performed with a small bolus of contrast. This can be exploited to obtain adjunct functional information on renal perfusion. We have investigated the potential of this to measure renal perfusion, to produce colour renal perfusion maps and to predict surgical outcome in infrarenal aortic aneurysm assessment. METHODS: We studied 21 patients being assessed for repair of infrarenal AAA. Prior to the spiral CT, a single level through the renal hili and aorta was scanned after the intravenous injection of 25 ml of contrast given at 10 ml/s. Ten 1 s duration scans were performed from 8 to 30 s after injection. Optimal timing for CT angiography can then be determined. Time-density curves were then drawn for both kidneys and aorta using regions of interest (ROIs) or pixel-by-pixel analysis. Renal cortical perfusion was measured using both ROI analysis and pseudocolour perfusion images. Following previous work, perfusion was calculated as the peak upslope of the tissue time density curve divided by peak aortic enhancement. RESULTS: Cortical mean perfusion averaged 2.48 ml/min per ml (range 0.8-3.7 ml/min per ml n = 34) and the values obtained agreed with literature expectations. Follow up in the 10 patients proceeding to AAA repair suggest low mean perfusion values and predict a raised postoperative creatinine (P < 0.05) CONCLUSIONS: Additional functional data and imaging can be obtained from the initial timing scan of a CT study, without requiring a dedicated study.

Impaired vasoconstriction of peripheral cutaneous blood flow in Type 1 diabetic patients following food ingestion.

Abnormalities in cutaneous blood flow (CBF) in otherwise healthy subjects with Type 1 diabetes mellitus (DM) have been demonstrated in response to local insults to the skin. To investigate whether defects also occurred in response to a regular daily activity, CBF was measured with laser Doppler flowmetry (LDF), before and 20 min after starting a mixed meal in 13 male Type 1 DM subjects with no clinical evidence of neuropathy, nephropathy or macroangiopathy and compared to 7 non-diabetic controls. Diabetic subjects and controls were of similar age and body mass index (mean +/- SD, 33.7 +/- 7.4 vs 37.1 +/- 9.2 years and 25.2 +/- 2.9 vs 24.5 +/- 2.9 kg m(-2), respectively). In subjects with DM, HbA1c was 8.3 +/- 0.6% (normal range 4-5.5%) and duration of diabetes was 18 (8-38) years, median (range). Following a mixed meal the CBF fell in the controls by 36% (24 to 56), median (range), compared to 3% (-5 to 18) in Type 1 DM subjects, P < 0.0005. These results show there is a normal physiological fall in CBF following food ingestion which is attenuated in Type 1 DM. These abnormalities of vasoconstriction in the peripheral microcirculation are present after 8 years of diabetes and precede the development of clinically apparent neuropathy or vascular disease.

Pre-operative classification of abdominal aortic aneurysms with spiral CT: the axial source images revisited.

OBJECTIVE: The differentiation of supra-, juxta- and high infrarenal abdominal aortic aneurysms (AAA), which is essential for good surgical management, remains problematic. This prospective study assessed the value of highly overlapping vs. contiguous axial spiral computed tomography (CT) reconstructions in the pre-operative assessment of AAA. PATIENTS AND METHODS: Thirty-five patients with abdominal aortic aneurysms were studied with spiral CT (10 mm collimation, pitch 1). Axial reconstructions were performed at 2 and 10 mm increments and compared with surgical findings. Using each protocol, the aneurysms were classified as infra-, juxta- or suprarenal. Observers also assessed visualization of main and accessory renal artery origins and identification of other surgically relevant vascular anomalies. RESULTS: The 2 mm protocol correctly identified 29/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; two infrarenal aneurysms were overestimated as suprarenal. The 10 mm protocol correctly classified 25/31 infrarenal, 3/3 juxtarenal and 1/1 suprarenal aneurysms; five infrarenal aneurysms were overestimated as juxtarenal (n = 3) or suprarenal (n = 2) and one case was equivocal. Correct classification was thus 94% using the 2 mm protocol and 83% with the 10 mm protocol (P = 0.063). All 70 main renal artery origins were visualized with the 2 mm protocol, while the 10 mm protocol missed six (P = 0.03) The 2 mm protocol identified 10 accessory renal arteries, four of which were missed by the 10 mm protocol. Both protocols demonstrated five surgically relevant venous anomalies. CONCLUSION: Spiral CT with highly overlapping axial reconstructions correctly classified 94% of abdominal aortic aneurysms; overlapping reconstructions were particularly useful in differentiating high infrarenal from juxtarenal aneurysms.