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ORIGINAL ARTICLE
Year : 2020  |  Volume : 23  |  Issue : 3  |  Page : 310-314

Abdominal aortic diameter and its determinants among healthy adults in Port Harcourt, Nigeria


1 Department of Radiology, Federal Medical Centre, Owerri, Imo State, Nigeria
2 Department of Radiation Medicine, University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu State, Nigeria
3 Department of Radiology, University of Port Harcourt Teaching Hospital, Rivers State, Nigeria

Date of Submission17-Jan-2019
Date of Acceptance29-Dec-2019
Date of Web Publication5-Mar-2020

Correspondence Address:
Dr. U M Ezenwugo
Department of Radiology, Federal Medical Centre Owerri, Imo State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_33_19

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   Abstract 


Background: The abdominal aorta is the largest artery in the human body. Sonographic assessment of the abdominal aortic diameter is presently the preferred screening method for an aortic aneurysm. However, there are no customized nomograms for our population and the recommended cutoffs for screening may be inappropriate. The effect of factors such as age, gender, and body mass index (BMI) on the abdominal aortic dissection (AAD) among blacks has also not been extensively investigated. Objective: To develop a nomogram of AAD at various levels in Nigerian adults using high-resolution B mode ultrasonography and to evaluate the effect of factors such as gender, age, and BMI on AAD. Methodology: This study involved a sonographic evaluation of the abdominal aortic diameter of 400 normal Nigerian adults aged 18 years and above over a period of 17 months. The scan was done using a 3.5–5 MHz curvilinear transducer on the Mindray ultrasound machine (model: DC-8, SN-QE3B001806). The AAD (mean ± SD) was correlated with age, gender, BMI, and body surface area (BSA). Data were analyzed using SPSS version 20 for windows and P values <0.05 were considered significant. Results: The mean AADs decreased from 1.58 ± 0.24 cm in the upper aorta (D1) to 1.40 ± 0.20 cm at the level of the renal arteries (D2) and 1.29 ± 0.23 cm at the bifurcation (D3). Mean AAD was significantly higher at all levels of the abdominal aorta (D1, D2, and D3) in males than in females (P < 0.00) and correlated positively with age (P = 0.00) and height (P = 0.00) at D2 and D3 levels. Conclusion: Absolute AADs were relatively smaller in adult Nigerians and this should be considered when setting up screening programs for abdominal aortic aneurysm in our population. Further studies are needed to determine factors affecting AAD.

Keywords: Abdominal aortic diameter, hypertension, ultrasonography


How to cite this article:
Ezenwugo U M, Okwudire E G, Njeze N R, Maduforo C O, Moemenam O O. Abdominal aortic diameter and its determinants among healthy adults in Port Harcourt, Nigeria. Niger J Clin Pract 2020;23:310-4

How to cite this URL:
Ezenwugo U M, Okwudire E G, Njeze N R, Maduforo C O, Moemenam O O. Abdominal aortic diameter and its determinants among healthy adults in Port Harcourt, Nigeria. Niger J Clin Pract [serial online] 2020 [cited 2020 Apr 6];23:310-4. Available from: http://www.njcponline.com/text.asp?2020/23/3/310/280028




   Introduction Top


The diagnosis and clinical decisions regarding the management of abdominal aortic aneurysms (AAA) are determined by the knowledge of the normal abdominal aortic diameter.[1] The pattern of AAA varies between countries depending on ethnic, geographical differences, and the burden of risk factors.[2] The lifetime prevalence of AAA is estimated between 1.3% and 8.9% in men and 1.0% and 2.2% in women in the United States of America.[3] There is a paucity on the prevalence of AAA among Nigerians. While uncommon, ruptured AAA is catastrophic with high mortality rates,[4] it is necessary to identify individuals with this condition early enough by screening individuals at risk. Sonographic assessment of the abdominal aortic diameter is presently the preferred screening method for AAA and the effect of factors, such as age, gender, and body mass index (BMI) on the abdominal aortic dissection (AAD) have been studied by a variety of researchers among Caucasian populations.[5],[6] However, there are no customized nomograms for our population and the recommended cutoffs for screening may be inappropriate as they are based on Western demographic data.

The purpose of this study was to develop a nomogram of AAD in normal adults using high-resolution B mode ultrasonography and to evaluate the effect of factors such as gender, age and BMI on AAD.


   Materials and Methods Top


This was a cross-sectional study involving 400 healthy adult volunteers randomly chosen from members of staff, medical students, patients' relatives, and members of the public. The study spanned a period of 17 months. The approval to carry out this study was obtained from the ethical committee of the institution reference number: UPTH/ADM/90/S.II/VOL.X/397.

Individuals were required to fill a short questionnaire that was used for inclusion/exclusion. Exclusion criteria included hypertension, pregnancy, presence of an abdominal mass on ultrasound, cigarette smoking which is known to independently increase AAD[7],[8] and diabetes mellitus (fasting blood glucose ≥7.0 mmol/L), since it may cause a decrease in AAD.[9],[10],[11] Informed consent was obtained from each participant and their weight and height were measured using a dual weight and height measuring scale. Blood pressure was also measured on the left arm using a mercury sphygmomanometer with the participant seated, after a minimum of 5 min of rest. Fasting blood sugar using ACCU-CHECK® glucometer, was done in the mornings between 8 and 9 am to exclude diabetic patients.

Ultrasound examinations were preferably done in the morning following overnight fast by subjects to reduce bowel gas and provided a better view of the abdominal aorta[12] using real-time ultrasound scanner (Mindray model: DC-8, SN-MU98001687, Keji China, 2013), with a 3.5 MHz transducer with freeze-frame capability and on-screen caliper for measurement. With the patient lying comfortably in the supine position, coupling gel was applied and the probe was placed over the abdomen in a longitudinal scan just below the xiphisternum and the aorta was identified as a throbbing hypoechoic tubular structure with echogenic walls running down the abdomen slightly to the left of the midline. The measurements of the internal diameter were taken from intima to intima (in plaque-free areas) at peak systole with the patient lying supine.

Measurements of the maximum aortic anterior–posterior (AP) diameter were measured using onscreen calipers, in longitudinal and transverse planes were taken at three levels. The measurement of the upper aorta (D1) was taken at the level of the superior mesenteric artery [Figure 1]. D2 at the origin of the renal arteries [Figure 2] and D3 at the bifurcation into common iliac arteries [Figure 3].
Figure 1: Sonogram showing a measurement of the upper abdominal aorta (D1 in CM) at the level of the superior mesenteric artery (SMA) in the longitudinal plane

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Figure 2: Sonogram showing a measurement of the mid abdominal aorta (D2 in CM) at the level of the renal artery in the transverse plane

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Figure 3: Sonogram showing a measurement of the lower abdominal aorta (D3 in CM) at the level of bifurcation in a longitudinal plane

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Data were recorded on the study datasheet and analyzed using Statistical Package for Social Sciences (SPSS), software version 20 (IBM Corp., Armonk, New York). Data were checked for normality using the Shapiro-Wilk test while X2 was used to analyze the relationship between AAD and gender while Pearson's correlation coefficient was used to assess the relationship of abdominal aortic diameter with age and BMI. Regression analysis was done to determine the contribution of these indices to aortic diameter. P values of <5% were considered statistically significant.


   Results Top


The demographic characteristics of participants are summarized in [Table 1]. There were more females in the group compared to males 205 (51.3%) vs 195 (48.7%). The mean age of participants was 51.13 ± 16.71 years [Table 1] with most being less than 40 years. The majority (57.8%) of participants were of normal weight, while 14.5% were obese. [Figure 4] shows that there were more females in the younger age groups while males predominated above 60 years.
Table 1: Demographic characteristics of the participants

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Figure 4: Bar chart showing age and gender distribution of participants

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The cumulative mean abdominal aortic diameters (as shown in [Table 2]) were 1.58 ± 0.24 cm for the upper abdominal aorta (D1), 1.40 ± 0.20 cm at the level of the renal arteries (D2), and 1.29 ± 0.23 cm at the bifurcation (D3).
Table 2: Cumulative mean abdominal aortic diameters

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When the mean AAD was compared between males and females [Table 3], the values were significantly higher at all levels of the abdominal aorta (D1, D2, and D3) in males than in females (P < 0.001). Males had a mean AAD of 1.65 ± 0.26 cm at the upper abdominal aorta, 1.47 ± 0.21 cm at the mid-level and 1.38 ± 0.23 cm at the bifurcation while female non-hypertensive participants had a mean AAD of 1.51 ± 0.20 cm, 1.34 ± 0.16 cm, and 1.21 ± 0.19 cm at the corresponding levels. The AAD showed a decrease in diameter from the upper to the middle to lower portions. This was consistent in both sexes.
Table 3: Comparison of mean AAD according to gender, at the upper (D1), mid (D2), and lower (D3) abdominal aorta

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A significant positive correlation was found between age and AAD at all levels of the abdominal aorta [Figure 5], [Figure 6], [Figure 7] as well as between BSA and AAD at the mid abdominal aorta [Figure 8]. Summary of correlation between age, weight, height, BMI and BSA is shown in [Table 4].
Figure 5: Plot showing the relationship between age and upper abdominal aortic diameter

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Figure 6: Plot showing the relationship between age and mid-abdominal aortic diameter

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Figure 7: Plot showing the relationship between age and lower-abdominal aortic diameter

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Figure 8: Plot showing relationship between body surface area and mid-abdominal aortic diameter

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Table 4: Correlation of mean AAD with biophysical characteristics at the upper (D1), mid (D2), and lower (D3) abdominal aorta

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Multiple regression done for factors which correlated significantly with AAD yielded a model which was much better than a guess (P = 0.00) but could not explain most of the variation in A1 (F = 10.07, adjusted R2 = 0.12), A2 (F = 8.78, adjusted R2 = 0.11) and A3 (F = 7.96, adjusted R2 = 0.10).


   Discussion Top


The index cross-sectional study carried out on healthy volunteers demonstrated a decrease in aortic diameter from 1.58 ± 0.24 cm in the upper aorta (D1) to 1.40 ± 0.20 cm at the level of the renal arteries (D2) and 1.29 ± 0.23 cm at the bifurcation (D3). This trend is similar to the findings by Joh et al.[6] who reported diameters of 2.14 cm, 1.95 cm, and 1.83 cm for the suprarenal, renal, and infrarenal aorta was respectively and Usman et al.,[13] who reported mean suprarenal and infrarenal AADs to be 1.79± (0.25) cm and 1.63± (0.23) cm, respectively. The actual AAD at each level was, however, smaller in our study at each level compared to this study. This may be as a result of racial variations and the fact that AAD was measured on computed tomography in those studies.

Several studies have evaluated the relationship between gender and AAD. We found a significantly higher AAD among males participants compared to females for the upper, mid and lower aorta (P = 0.00). This is similar to the findings of other studies.[4],[11],[14],[15],[16],[17] Laughlin et al.[18] carried out in 1926 adults, infrarenal AAD was found to be significantly larger (P < 0.001) in men than women and this relationship was independent of age, body surface area and ethnicity.

A significant positive correlation between age and AAD was observed in the index study and is similar to the findings of Joh et al.[6] who reported that the mean infrarenal aortic diameter measured 1.75 cm for people in their 50 s, 1.81 cm for people in their 60 s and 1.94 cm for people in their 70 s. Valecchi et al.[17]assessed the internal aortic diameters of 250 normal subjects and found a positive correlation of increasing AAD with age. Our findings also agree with findings reported by other researchers.[11],[19],[20],[21]

The influence of BMI on AAD has been controversial. We found no correlation of BMI with AAD at the upper (P = 0.70), mid (P = 0.79), or lower aorta (P = 0.50) and is in consonance with findings of Takagi et al.[22] and Stackelberg et al.[23] found no significant relationship between BMI and AADs. In contrast, Jasper et al.[1] in their study of healthy adults found that subjects with increased BMI had relatively larger abdominal aortic diameters (P < 0.001). Esposito et al.[24] also reported that among participants in a screening program for AAA, increasing AAD was positively related to BMI (P < 0.0001) while Norman et al.[21] also found an independent association of BMI with increasing AAD. This relationship may also be due to the effect of confounding variables and no regression analysis was done to determine the actual contribution of BMI to AAD unlike in the index study.


   Conclusion Top


Absolute AADs obtained at the supra-renal, renal, and infra-renal levels were relatively smaller in adult Nigerians and this should be considered when setting up AAA screening programs for our population. AAD was significantly higher among males and increased with age in both groups. No correlation with BMI was observed.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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