Normal Abdominal Aortic Diameter in the Southern Thai Population by Multidetector Computed Tomography

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1 102 «æ å ªï Ë 39 Ë 2 π- ÿπ π 2557 π æπ åμâπ Normal Abdominal Aortic Diameter in the Southern Thai Population by Multidetector Computed Tomography Bootpheaw T Department of Radiology, Krabi General Hospital ËÕß àõ» π ª μ ÕßÀ Õ Õ ß ÕÕÕ åμ «àõß âõß π π μâ μ «â«ëõß Õ å Õ æ «μõ å μ å æ π å ÿμ ºâ«ÿà ß π ß «ßæ Ë «æ å 2557; 39: » π ª μ ÕßÀ Õ Õ ß ÕÕÕ åμ «àõß âõß π π μ «â«ëõß Õ å Õ æ «μõ å μ å π ßæ Ë ºŸâ» â «π âπºà»ÿπ å ß ÕßÀ Õ Õ ß ÕÕÕ åμ «àõß âõß π π π«π 282 ªìπºŸâªÉ«160 À ß 122 æ Õ å Õ æ «μõ å π μ å à«π àõß âõß π à«ß Õπ ÿπ π æ.» ß Õπæƒ æ.» àß ªìπ 4 ÿà μ à«ßõ ÿ âõ Ÿ Ë âπ «Àå À «æ π å Õß π âπºà»ÿπ å ß ÕßÀ Õ Õ ß Õ ÿ æ» ««â ß Õß Ÿ πà ß æ «à ºŸâªÉ«ÿ ÕßÀ Õ Õ ß ÕÕÕ åμ Ëß àõ Ê π ß à«π suprarenal π ß à«π infrarenal π âπºà»ÿπ å ß Ë ÕßÀ Õ Õ ß ÕÕÕ åμ à«π suprarenal «Ë Ÿ πà ß à«π «ßÕ Èπ Ë 12 π æ» Õ 19.91±2.87 μ π æ»à ß Õ 17.94±2.41 μ π Ë π âπºà»ÿπ å ß Ë ÕßÀ Õ Õ ß ÕÕÕ å μ à«π infrarenal «Ë Ÿ πà ß à«π Õ«Èπ Ë 3 π æ» Õ 14.97±2.14 μ π æ»à ß Õ 13.34±2.08 μ Õ μ à«π Õß π À Õ Õ ËÕ ª À«à ßÀ Õ Õ à«π infrarenal À Õ Õ à«π suprarenal π æ» Õ 0.78±0.09 π æ»à ß Õ 0.77±0.09 À Õ Õ μμ Õ ÿæ «à π ÕßÀ Õ Õ ÕߺŸâ μ «à Õß ºŸâÀ ß π Èß Õß Õ à ß π ß μ Ë p < 0.01 Ë π ÕßÀ Õ Õ ««â ß Õß Ÿ πà ß Á «æ π å πõ à ß π ß μ Ë p < 0.01 â«àπ π ÿª» π È Àâ π ª μ ÕßÀ Õ Õ ß ÕÕÕ åμ «àõß âõß à«π suprarenal à«π infrarenal π π μâ Ëßæ «à π ß à ««æ π å Õ ÿ æ» π Õß Ÿ πà ßÕ à ß π ß μ Õ à ß Áμ π Ë ÕßÀ Õ Õ ÕÕÕ åμ π π π Á «à π ÕßÀ Õ Õ ÕÕÕ åμ Ë ß π π «ß«Õß «μ «πμ : π ª μ ÕßÀ Õ Õ ß ÕÕÕ åμ «àõß âõß ËÕß Õ å Õ æ «μõ å μ å Abstract The author retrospectively reviewed the multidetector computed tomography (MDCT) data of two hundred and eighty-two patients who underwent contrast-enhanced MDCT scan of the abdomen for noncardiovascular reasons in Krabi General Hospital during June 2013 to May The mean internal diameters of the suprarenal and infrarenal abdominal aortas were measured at the T12 and L3 vertebral levels. Aortic sizes were analyzed and correlated by age, gender and vertebral body width. The mean diameters of the suprarenal and infrarenal abdominal aortas measured at T12 and L3 vertebral levels were

2 Vol. 39 No. 2 April-June Bulletin of the Department of Medical Services 19.91±2.87 mm. and 14.97±2.14 mm. in men and 17.94±2.41 mm. and 13.34±2.08 mm. in women, respectively. The ratio of the infrarenal to the suprarenal abdominal aortic diameters was 0.78±0.09 in men and was 0.77±0.09 in women. The abdominal aortic diameter progressively increased in caliber with the increasing age of the patients and was larger in men than women. Significant positive correlation was found between the abdominal aortic diameter and the vertebral body width in both men and women. In conclusion, among the Southern Thai people, the mean diameters of the abdominal aortas were determined at each level. The abdominal aortic diameters correlated with age, gender and vertebral body width, as same as previously published literatures. However, the abdominal aortic diameters of the Southern Thai population were less than that of the Western population. Key words: Normal abdominal aortic diameter, Multidetector computed tomography Introduction The infrarenal aortic diameter has been of interested in the cortex of abdominal aortic aneurysm. Now, the threshold of 3 cm. is commonly accepted as indicating the presence of an abdominal aortic aneurysm (AAA) and therapeutic intervention should be undertaken at diameter of cm., due to risk of ruptured. 1-3 Some studies suggested that a threshold diameter of 2.6 cm. is recommended for screening as an ectatic aorta. 4 Knowledge of the normal abdominal aortic diameter in the Thai population would be useful in the management of patients presenting with abdominal aortic abnormality. There is limited data about the abdominal aortic diameter in the Thai population. Furthermore, diagnostic criteria and treatment guidelines of diseases of the abdominal aorta in Thailand are still using data which were mentioned in Western literatures. It is apparent that the average body size of Thai people is smaller than that of Western people. Hence, normal abdominal aortic diameter of Thai population should be smaller than that of Western population. Therefore, treatment protocols for intervention are likely to be different. Criteria for management decisions would change if normal abdominal aortic diameters vary significantly in the Thai population as opposed to elsewhere. Having 10 years of experience in diagnostic radiology (3 years for the residency training program and 7 years working as a diagnostic radiologist), the author suggests that abdominal aortic diameter measurement will be available without additional cost or effort during a MDCT scan of the abdomen for any reasons. This prompted the author to study the normal diameter of the abdominal aorta at the suprarenal and infrarenal portions in Thai people, to establish the normal standard for the Thai population by using multidetector computed tomography. Materials and Methods MDCT Protocol All CT scans of the abdomen were performed using a 16-slice multidetector CT (MDCT) scanner.contrast scans were acquired after an antecubital or cephalic intravenous injection of about ml. of Ultravist (Iopromide : nonionic iodinated contrast material containing 300 mg./ml. iodine). The injection rate was ml./sec. The helical CT scan was performed with a delayed 90-

3 104 «æ å ªï Ë 39 Ë 2 π- ÿπ π sec. after starting injection. The MDCT parameters were 120 KVp, mas, 750 ms. TI and 7 mm. slice thickness. Inclusion criteria: The medical records of all patients who underwent MDCT scans of the abdomen in Krabi General Hospital, Krabi, Thailand during 1 year (June 2013-May 2014) were retrospectively reviewed to prepared CT data. All consecutive adult patients, above the 20 to 60 years of age range who underwent helical contrastenhanced CT scans of the abdomen for noncardiovascular reasons were included. The mean and standard deviation of the abdominal aortic diameter in both genders in age groups of 20-30, 31-40, and years, were calculated. Measurements All measurements were done by the author. The images were reviewed by scrolling on diagnostic PACS work station. The window level was HU with 1,500 HU window width to measured the aortic lumen more accuracy. The internal diameters of suprarenal and infrarenal abdominal aortas were measured at T-12 and L-3 vertebral levels, respectively. The vertebral body widths were measured at the same slice images. Analysis Statistical analysis was performed using a computer software package. The correlation Figure 1 Sagittal and axial MDCT of the abdomen: (A) sagittal reconstruction shows mid aortic plan and measurement levels. (B) axial image at T-12 vertebral level and (C) axial image at L-3 vertebral level.

4 Vol. 39 No. 2 April-June Bulletin of the Department of Medical Services between age, gender, vertebral body width and aortic diameter was analyzed using the Pearson's correlation test and significance level at The student t-tests and chi squared tests were used to assess differences between groups at p-value < Result One hundred and sixty male and one hundred and twenty-two female patients between years of age were enrolled in the study. The mean age was 43.42±11.59 years in men and was 44.46±11.79 years in women. The mean diameter of suprarenal abdominal aorta, measured at the T12 vertebral level was 19.91±2.87 mm. in men and was 17.94±2.41 mm. in women. The mean diameters of infrarenal abdominal aorta, measured at L3 vertebral level were 14.97±2.14 mm. in men and 13.34±2.08 mm. in women. The mean diameters of suprarenal and infrarenal abdominal aortas for men and women in all age groups are given in Table 1. The overall mean aortic diameters of males are larger than that of females with statistical significance in both suprarenal and infrarenal portions. The average mean diameter of abdominal aortas at the infrarenal portion was smaller than that of the suprarenal portion in all age groups of both genders. The ratio of the infrarenal to suprarenal abdominal aorta was 0.78±0.09 in men and was 0.77±0.09 in women. The ratios of mean of the infrarenal to the suprarenal aortic diameters among different age groups are showed in Table 2. There was significant positive correlation between the age of the patient and the mean aortic diameter of the suprarenal and the infrarenal portions, measured at T12 and L3 vertebral levels in both men and women. Table 3 shows the correlation of mean aortic diameter with vertebral body width at T12 and L3 levels. There was positive correlation between the abdominal aortic diameter and the vertebral body width in both Table 1 The mean diameters of suprarenal and infrarenal abdominal aortas for men and women in all age groups Level Age (years) Mean diameter ± S.D. (mm.) Male (n=160) Female (n=122) p-value Suprarenal abdominal aortas (T12) ± ± ± ± ± ± ± ±1.88 Summary 19.91± ± ** Infrarenal abdominal aortas (L3) ± ± ± ± ± ± ± ±1.78 Summary 14.97± ± ** Sig ** p<0.01

5 106 «æ å ªï Ë 39 Ë 2 π- ÿπ π 2557 genders in all age groups. Discussion Aortic diameter is of more significance than simply being used to diagnosis an abdominal Figure 2 Line presentation of mean aortic diameter and age. The mean aortic diameter increased with age at all levels with statistical significance (p< 0.01) aortic aneurysm. 1 Abnormally enlarged and too small aortas are associated with adverse cardiovascular outcomes. The diameter of the infrarenal abdominal aorta may have a role as simple marker of global cardiovascular risk. 5,6 In this study, the mean diameter of suprarenal abdominal aortas, measured at the T12 vertebral level was 19.91±2.87mm. in men and was 17.94±2.41 mm. in women. The mean diameters of infrarenal abdominal aortas, measured at L3 vertebral level were 14.97±2.14 mm. in men and 13.34±2.08 mm. in women. In the Jasper study, using computed tomography to evaluate normal abdominal aortic diameters in the Indian population in 2014, the mean diameter of the suprarenal abdominal aorta Figure 3 Line presentation of mean aortic diameter of a male and a female in each level. The mean aortic diameter of a male is larger than that of a female at all levels with statistical significance (p<0.01) Table 2 The ratios of mean of infrarenal to suprarenal aortic diameters among different age groups Age groups Mean ratio in each group Male (n= 160) Female (n=122) ± ± ± ± ± ± ± ±0.09 Summary 0.78± ±0.09 Table 3 The correlation of mean aortic diameter with vertebral body width at T12 and L3 levels. Vertebral width of males Vertebral width of females Aortic Level Pearson's p-value Pearson's p-value correlation (r) correlation (r) Suprarenal abdominal aortic diameter ** Infrarenal abdominal aortic diameter ** Sig **p<0.01

6 Vol. 39 No. 2 April-June Bulletin of the Department of Medical Services Male Female Figure 4 (a) Scatter plot of the suprarenal aortic diameter measured at T 12 level (AD_T12, mm.) and vertebral body width (VW_T12, mm.) of male and female. Male Female Figure 4 (b) Scatter plot of the infrarenal aortic diameter measured at L3 level (AD_L3, mm.) and vertebral body width (VW_L3, mm.) of male and female. in men was 19.0±2.3 mm. and in women was 17.1±2.3 mm.. The mean diameter of infrarenal abdominal aorta was 13.8±1.9 mm. in men and was 12.0±1.6 mm. in women. The mean aortic diameter of the Southern Thai people was slightly larger than that of the Indian population at all levels in both genders. 7 Infrarenal aortic diameter measured using ultrasound screening in unselected adult in Australian population by Norman, usually range from cm. in women and cm. in men. 1 The Sariosmanoglu study, the mean aortic diameter measured at the subdiaphragmatic level, was 18±3 mm. in women and was 19±4 mm. in men. 8 The normal reference values for upper limit of normal abdominal aortic diameter measured using MRI in the Swedish population of people over 70 years by

7 108 «æ å ªï Ë 39 Ë 2 π- ÿπ π 2557 Wanhainen were 3 cm. in men and 2.7 cm. in women. 9,10 The aortic diameters in this study were less than that obtained in the various studies available in the Western and Australian populations. The mean aortic diameters had progressively increased values with increasing age in both the suprarenal and infrarenal aorta in both genders The mean aortic diameter of male patients is larger than that of female patients, at all levels which is similar to the previous studies. The positive correlation of vertebral body width and aortic diameter was similar to the Euathrongchit and Aronberg studies. 11,12 This could be because the body size and vertebral body width of men are larger than that of women. Not surprisingly, some studies suggest that various measures of body habitus, more commonly height, weight, body mass index and body surface area have been associated with aortic diameter. Regarding the result of this study and previous studies, the abdominal aortic diameter can vary considerably in different patients. In an individual patient, the abdominal aorta should taper in a consistent fashion along its length. The ratio of infrarenal to suprarenal abdominal aortic diameters should normally be less than 1. The abdominal aorta should be considered abnormal if the aortic diameter exceeds the mean for a given age by at least two standard deviations. 11 In the Cardiovascular Health Study, the risk of cardiovascular mortality seem to increase with aortic diameters over 30 mm. or if the ratio of the infrarenal to suprarenal aortic diameter exceeds The use of standard values of the abdominal aortic diameter in this study will enable confident distinction between a normal and an abnormal abdominal aorta based on MDCT of the abdomen in the Thai population. Conclusion Abdominal aortic diameter measurement will be available without additional cost or effort, during MDCT of the abdomen for any reasons. Among the Southern Thai people, the mean diameters of abdominal aortas were determined at each level. The abdominal aortic diameter correlated with age, gender and vertebral body width, which is similar to previously published studies. However, the abdominal aortic diameters of the Thai population were less than that of Australian and Western populations but slightly larger than that of the Indian population. Therefore, this should be considered while performing computed tomography reports of abdominal aortic abnormality in different populations. Acknowledgement The author wishes to thank Mr. Chitchanin Niyomthai, the statistician at Krabi General Hospital for his statistical analysis. References 1. Norman PE, Muller J, Golledge J. The cardiovascular and prognostic significance of the infrarenal aortic diameter. J Vasc Surg 2011;54: Lederle FA, Johnson GR, Wilson SE, Gordon IL, Chute EP, Littooy FN, et al. Relationship of age, gender, race, and body size to infrarenal aortic diameter. The Aneurysm Detection and Management (ADAM) Veterans Affairs Cooperative Study Investigators. J Vasc Surg 1997;26: Lederle FA, Johnson GR, Wilson SE, Ballard DJ, Jordan WD Jr, Blebea J, et al. Rupture rate of large abdominal aortic aneurysms in patients refusing or unfit for elective repair. JAMA 2002;287: Devaraj S, Dodds SR. Ultrasound surveillance of ectatic abdominal aortas. Ann R Coll Surg Engl 2008;90:

8 Vol. 39 No. 2 April-June Bulletin of the Department of Medical Services 5. Greenland P, Smith SC Jr, Grundy SM. Improving coronary heart disease risk assessment in asymptomatic people: role of traditional risk factors and noninvasive cardiovascular tests. Circulation 2001;104: Pasternak RC, Abrams J, Greenland P, Smaha LA, Wilson PW, Houston-Miller N. 34th Bethesda Conference: Task force #1-Identification of coronary heart disease risk: is there a detection gap? J Am Coll Cardiol 2003;41: Jasper A, Harshe G, Keshava SN, Kulkarni G, Stephen E, Agarwal S. Evaluation of normal abdominal aortic diameters in the Indian population using computed tomography. J Postgrad Med 2014;60: Sariosmanoglu N, Ugurlu B, Karacelik M, Tuzun E, Yorulmaz I, Manisali M, et al. A multicentre study of abdominal aorta diameters in a Turkish population. J Int Med Res 2002;30: Wanhainen A, Themudo R, Ahlström H, Lind L, Johansson L. Thoracic and abdominal aortic dimension in 70-year-old men and women-a population-based whole-body magnetic resonance imaging (MRI) study. J Vasc Surg 2008;47: Wanhainen A. How to define an abdominal aortic aneurysminfluence on epidemiology and clinical practice. Scand J Surg 2008;97: Euathrongchit J, Deesuwan P, Kuanprasert S, Woragitpoopol S. Normal thoracic aortic diameter in Thai people by multidetector computed tomography. J Med Assos Thai 2008;92: Aronberg DJ, Glazer HS, Madsen K, Sagel SS. Normal thoracic aortic diameters by computed tomography. J Comput Assist Tomogr 1984;8: