A proposal for standardizing computed tomography reports on abdominal aortic aneurysms

Abstracts

OBJECTIVE: To propose a model to standardize computed tomography reports on abdominal aortic aneurysms. MATERIALS AND METHODS: Interviews were carried out with members of Vascular Surgery Division of our institution, in the period between April and October 2004, aiming at developing a standardized model of computed tomography reports on abdominal aortic aneurysms. Based on this model, a questionnaire was elaborated and sent to other nine surgeons, all of them experienced in the field of abdominal aortic surgery. The questionnaires response rate was 55.5% (5/9). RESULTS: The most frequently mentioned parameters of interest for evaluation of abdominal aortic aneurysms were: maximum diameter of proximal aortic neck, proximal aortic neck length to lower renal arteries, shape of proximal aortic neck, maximum diameter of the aneurysm and diameter of the common iliac arteries. These data allowed the development of a proposal for a model to standardize computed tomography reports. CONCLUSION: A model for standardized tomographic analysis of abdominal aortic aneurysms has met vascular surgeons' needs for following-up patients and planning their treatment.

Aorta; Aneurysm; Computed tomography

OBJETIVO: Propor um modelo de padronização de relatório para aneurisma da aorta abdominal na tomografia computadorizada. MATERIAIS E MÉTODOS: Foram realizadas, no período de abril a outubro de 2004, entrevistas com integrantes da Disciplina de Cirurgia Vascular da nossa instituição, para elaboração de um modelo de padronização de relatório de tomografia computadorizada para o estudo do aneurisma da aorta abdominal. A partir deste modelo foi elaborado um questionário, enviado a nove outros cirurgiões, todos com experiência em cirurgia da aorta abdominal. O índice de resposta aos questionários foi de 55,5% (5/9). RESULTADOS: Os parâmetros de interesse citados mais freqüentemente para a avaliação dos aneurismas de aorta abdominal foram: diâmetro máximo do colo proximal, extensão do colo proximal até a artéria renal mais baixa, forma do colo proximal, diâmetro máximo do aneurisma e diâmetro das artérias ilíacas comuns. Estes dados permitiram elaborar uma proposta de modelo para padronização de relatório na tomografia computadorizada. CONCLUSÃO: Um modelo para a análise tomográfica padronizada do aneurisma de aorta abdominal permite atender às necessidades dos cirurgiões vasculares para acompanhar a evolução e planejar o tratamento destes pacientes.

Aorta; Aneurisma; Tomografia computadorizada

ORIGINAL ARTICLE

A proposal for standardizing computed tomography reports on abdominal aortic aneurysms^*

Fabiola Goda Torlai^I; Gustavo S. Portes Meirelles^I; Fausto Miranda Jr.^II; José Honório A.P. da Fonseca^III; Sérgio Ajzen^IV; Giuseppe D'Ippolito^V

^IMD, Radiologists

^IIProfessor, Private Docent at Department of Surgery, Discipline Vascular Surgery, Universidade Federal de São Paulo-Escola Paulista de Medicina

^IIIProfessor, Private Docent at Department of Surgery, Discipline Cardiovascular Surgery, Universidade Federal de São Paulo-Escola Paulista de Medicina

^IVAdjunct Professor, Private Docent at Department of Imaging Diagnosis, Universidade Federal de São Paulo-Escola Paulista de Medicina

^VAdjunct Professor at Department of Imaging Diagnosis, Universidade Federal de São Paulo-Escola Paulista de Medicina

^{Mailing Address}

ABSTRACT

OBJECTIVE: To propose a model to standardize computed tomography reports on abdominal aortic aneurysms.

MATERIALS AND METHODS: Interviews were carried out with members of the Vascular Surgery Division of our institution, in the period between April and October 2004, aiming at developing a standardized model of computed tomography reports on abdominal aortic aneurysms. Based on this model, a questionnaire was elaborated and sent to other nine surgeons, all of them experienced in the field of abdominal aortic surgery. The questionnaires response rate was 55.5% (5/9).

RESULTS: The most frequently mentioned parameters of interest for evaluation of abdominal aortic aneurysms were: maximum diameter of proximal aortic neck, proximal aortic neck length to lower renal arteries, shape of proximal aortic neck, maximum diameter of the aneurysm and diameter of the common iliac arteries. These data allowed the development of a proposal for a model to standardize computed tomography reports.

CONCLUSION: A model for standardized tomographic analysis of abdominal aortic aneurysms has met vascular surgeons' needs for following-up patients and planning their treatment.

Keywords: Aorta; Aneurysm; Computed tomography.

INTRODUCTION

Aortic aneurysm is defined as an area of permanent dilatation of more than 50% normal diameter of aorta or of the segment immediately above the aneurysm⁽¹⁾. There are studies considering the abdominal aortic aneurysm as a dilatation greater than 3 cm in its largest true transverse dimension⁽²⁾.

Risk factors for abdominal aortic aneurysm are similar to those identified for symptomatic arteriosclerosis, including age of more than 50 years, male sex, smoking and chronic obstructive pulmonary disease⁽²⁾. Abdominal aortic aneurysms expand at a rate of 2–4 mm per year for aneurysms smaller than 4 cm, 2–5 mm per year for aneurysms between 4–5 cm and 3-7 mm for those larger than 5 cm. The rupture risk at 4 years is 2% for aneurysms smaller than 4 cm, 10% for 4–5 cm aneurysms and 22% for > 5 cm aneurysms^(3,4).

Studies have demonstrated an increase in aortic aneurysms incidence. Starting in the seventies thru the nineties, the incidence has doubled, with the improvement in imaging methods, principally due to the advent of computed tomography (CT) and also because of the increase in the population life expectancy⁽⁵⁾.

The objective of the treatment of aortic aneurysm is to exclude it from the arterial blood pressure, preserving the blood flow by means of a vascular conduit implant and eliminating the risk for rupture and death^(4,6).

The relevance of anatomic factors for determination of the patients conduct makes the imaging studies essential for evaluating aortic aneurysms, especially by means of standardized and easily comprehensible reports^(4,7).

Our objective was to propose a scheme for standardizing CT reports on abdominal aortic aneurysms.

MATERIALS AND METHODS

Interviews with 14 surgeons were carried out in the period between April and October 2004. Firstly, five docents of Vascular Surgery at Universidade Federal de São Paulo-Escola Paulista de Medicina (Unifesp-EPM), familiarized with the subject, to discuss the model for abdominal aortic aneurysm CT report. Then the following question was formulated: "Which parameters do you consider significant and that should be included in a CT report for evaluating a patient with abdominal aortic aneurysm?".

So, a CT report model was elaborated on the basis of the opinions expressed in the first interviews. Then, this model was sent via electronic mail with digital questionnaires to other nine surgeons specialized in aortic aneurysms, not bonded with Unifesp-EPM, and indicated by peers of this university. The questionnaires response rate was 55.5% (5/9).

Based both on the interviews carried out at Unifesp-EPM and the responses to the electronic questionnaires, we have performed a statistical analysis and elaborated a definite model of report for abdominal aortic aneurysm.

RESULTS

Results are displayed in Table 1. There was a consensus of opinions as regards the importance of inclusion in the report of measurements related to the aneurysm proximal neck diameter, proximal aortic neck length to the lower renal artery, shape of proximal aortic neck, maximum diameter of the aneurysm and diameter of the common iliac arteries. The aortic lumen diameter and internal iliac arteries patency has not been mentioned by the majority of respondents.

In Figure 1 we present a model suggesting a standard CT report for an abdominal aortic aneurysm analysis.

DISCUSSION

The first model of report on aortic aneurysm was published in 1997 by the Committee for Standardized Reporting Practices in Vascular Surgery of the Vascular Surgery Society/International Society for Cardiovascular Surgery, for infra-renal abdominal aortic aneurysms, covering clinical and anatomic aspects and based on angiography, CT and magnetic resonance imaging (MRI)⁽⁸⁾.

In 2002, the Committee for Standardized Reporting Practices in Vascular Surgery published an updating, originally defining criteria for post-endovascular procedure analysis. This consensus recommends that aneurysms are classified as per localization, etiology and clinical manifestation⁽⁶⁾.

Other authors have studied anatomical risk for endovascular repair of abdominal aortic aneurysm, rating parameters like proximal and distal aortic neck diameter, length and tortuosity; vessels and tortuosity originating from the aneurysmal sac; pelvic perfusion; iliac arteries diameter and tortuosity, among others^(9,10).

Some anatomical repairs must be defined for a systematic analysis of aortic aneurysms. The aneurysmal neck is defined as the aorta portion with a normal diameter immediately above or below the aneurysm and is the site where the graft is connected to the aorta, being effectively fixed and sealed⁽¹¹⁾. The distal aortic neck may be present or not, and the aneurysm may extend to iliac arteries. The measurement of the proximal aortic neck length should be performed in relation to the most distal renal artery, and from the distal neck in relation to the iliac bifurcation (Figure 2)^(9,12,13).

Figure 2 - click here to enlarge

The neck diameter should be measured perpendicularly to the blood flow. In cases where this is not perpendicular to the cut plane, the smallest measurement of diameter in elliptical cuts is considered an appropriate approximation of the true diameter measurement⁽⁴⁾. Some authors consider the neck angulation degree as a significant factor in the analysis of aortic aneurysms⁽⁹⁾, and this parameter has also been valued by the interviewed physicians.

The maximum aneurysmal diameter is one of the most important factors in the study of aortic aneurysms, considering that the rupture risk is related to the aneurysm size and expansion rate⁽⁴⁾. The maximum aneurysmal diameter should correspond to the wall-to-wall diameter, perpendicular to the blood flow or to the cut plane in 3D reconstructions (Figure 2). The smallest measurement of diameter in elliptical cuts is considered an appropriate approximation of the true diameter measurement⁽⁶⁾.

Although respondents have not put a high value on the distal aneurysmal neck diameter, it also is important, if present, for the choice of the type of endoprosthesis to be employed — bifurcated or mono-iliac.

The aneurysmal tortuosity also is another factor of interest in the anatomical evaluation of aortic aneurysms. The literature describes several methods for tortuosity grading^(8,9,14). The presence of thrombus in the aneurysm also should be analyzed. Some authors evaluate the quantity of thrombi through the size of the area occupied. Thrombi, associated with aneurysmal tortuosity and angulation, may increase the risk of periprocedural embolization in patients submitted to endovascular grafting⁽⁹⁾, and for this reason the aneurismal lumen diameter must be informed.

The presence of patent vessels originating from the aneurysmal sac also may influence the success of endovascular procedures and is considered as a risk factor in endovascular grafting^(9,15).

In the endovascular repair of aortic aneurysms, the iliac arteries anatomy is related to the access for the procedure, the perfusion to the pelvis and adjacent organs in abdominal aortic aneurysms, and to the presence of an endograft fixation site^(9,13). Complications connected with a difficult anatomy of iliac arteries are described in 47% of patients⁽¹⁶⁾ and this explains the relevance of data on this vessels caliber, patency and length (L3, L4, D3 and D4).

Finally, it is interesting to observe that a similar model of report may also be adopted for MR angiography (Figure 3), excluding the evaluation for the presence of parietal calcifications, hardly detected by this method.

CONCLUSION

Based on the analysis of the results obtained from interviews and questionnaires responded by surgeons directly involved in the treatment of abdominal aortic aneurysms, we may conclude that it is possible to establish a standard report with practical utility and tailor-made for meeting the needs of both patients and specialists.

REFERENCES

Received November 1st, 2005.

Accepted after revision November 28, 2005.

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*

Study developed at Universidade Federal de São Paulo-Escola Paulista de Medicina, São Paulo, SP, Brazil.

Publication Dates

• Publication in this collection
  26 Sept 2006
• Date of issue
  Aug 2006

History

• Received
  01 Nov 2005
• Accepted
  28 Nov 2005