Ultrasound assessment of the caliber of the arteries in the lower extremities in healthy persons - the dependency on age, sex and morphological parameters of the subjects.

AIM: The aim of this paper was to evaluate the caliber of the following arteries in the lower extremities: the common femoral artery, superficial femoral artery, popliteal artery, posterior tibial artery and dorsalis pedis artery and to determine the relation of the calibers to age, sex and morphological parameters of the body such as weight, height and BMI of the subject. MATERIAL: Two hundred and twenty-eight healthy persons aged 18-81 were examined (average ±SD; 43.1±16.71): 134 women aged 19-74 (43.2±15.63) and 94 men aged 18-81 (43±18.22).
METHODS: The study was conducted with the use of a linear probe of 7.5 MHz frequency. The vascular caliber was assessed after the color map (color Doppler) was placed on a B-mode image.
RESULTS: The average and standard deviation values for the calibers of examined vessels were determined. The calibers of all vessels examined in the group of men were statistically significantly larger than those in the group of women. No statistically significant differences between the calibers of the right and left sides were determined. The statistically significant correlations were specified between the age and the caliber of the examined vessels; positive for large femoral arteries and negative for the arteries of the crus and foot. Positive, statistically significant correlations between the caliber and the height, weight and BMI were also reported.
CONCLUSIONS: The reported calibers of the arteries in the lower extremities and their relation to age, sex and morphological parameters of the subjects enable the differentiation of the physiological remodeling of the vessels from the pathological processes in e.g. atherosclerosis or hypertension.

Introduction

Peripheral artery disease is the most common cause of lower extremity amputations and it constitutes an important risk factor of stroke or myocardial infarction(. It is becoming a great challenge for the health care system due to high social and economic costs. Currently, the researchers seek possibly cheap and, at the same time, reliable methods of diagnosing and monitoring the course of this disease.

Ultrasound examination (US) is the primary one in the diagnostics of the arterial diseases of the lower extremities. The analysis of the image encompasses both the morphological assessment of the vessels (B-mode image, color Doppler) as well as spectral evaluation of the blood flow (duplex Doppler) and the results are compared to the referential values of healthy subjects. Despite the indisputable development of imaging techniques, few papers have been published concerning the caliber of the arteries in the lower extremities in healthy persons, in particular regarding the arteries below the knee. The data available in the pertinent literature concern the assessment of single vessels or the study results are based on a small number of subjects(. All the more, it is difficult to find any publications concerning the relation of the caliber of the arteries in the lower extremities to age, sex and morphological parameters of the subjects.

The aim of this paper was to evaluate the calibers of the following arteries in the lower extremities: the common femoral artery – CFA, superficial femoral artery – SFA, popliteal artery – PA, posterior tibial arteries – PTA and dorsalis pedis artery – DPA and to determine the relation of the calibers to age, sex and morphological parameters of the body such as weight, height and BMI of the subject.

Material and methods

Two hundred and twenty-eight healthy persons aged 18–81 (average ±SD; 43.1±16.71): 134 women aged 19–74 (43.2±15.63) and 94 men aged 18–81 (43±18.22) were examined. The group of subjects comprised the hospital personnel, students and their relatives. The factors excluding from the study were among others: hypertension (SBP > 140 mm Hg and/or DBP > 90 mm Hg), smoking, obesity (BMI ≥ 30 kg/m2), peripheral artery disease (assessed on the basis of the ankle-brachial index – ABI, measured on the dorsalis pedis artery and the posterior tibial artery; the value ABI < 0.9 was considered abnormal). Tab. 1 presents the morphological parameters (height, weight, BMI) for the whole group and separately for men and women.

Tab. 1

Morphological parameters of the body in the groups of women, men and the entire group (women and men)

Morphological parameters	Women (n = 134)(average ±SD)	Men (n = 94)(average ±SD)	Entire group (n = 228)(average ±SD)
Height [m]	1,64±0,06	1,77±0,06	1,69±0,09
Weight [kg]	62,51±8,27	80,72±9,80	70,02±12,68
BMI [kg/m2]	23,31±2,83	25,69±2,62	24,29±2,99

The examinations were performed by a person with 5 years of experience in Doppler diagnostics (D.C.) with the use of a scanner (Siemens, Siemens Elegra, Erlangen, Germany) equipped with a linear probe with the average frequency of 7.5 MHz (B-mode: 5.1–9.0 MHz; color Doppler: 5.1–6.5 MHz). The subjects were examined after a 10-minute rest in the supine position (while assessing CFA, SFA, PTA, DPA) and in the prone position (while assessing PA). The measurements of the DPA were conducted after bending the subject's lower extremity in the knee joint at the angle of 90°. The vessel caliber was assessed after the color map (color Doppler) was placed on a B-mode image. The parameters of the Doppler examination were adjusted individually to the size of the vessel in order to eliminate possible artifacts: the frequency of impulse repetitions (range: 868–3125 Hz), color enhancement (range: 70–78 dB). The measurements of the calibers were conducted at the following levels:

the common femoral artery – 3 cm above the branching;

the superficial femoral artery – 3 cm below the CFA branching;

the popliteal artery – 3 cm above the origin of the anterior tibial artery;

the posterior tibial artery – in the region of the medial malleolus;

the dorsalis pedis artery – in the region of the neck of the talus bone.

The obtained results were statistically analyzed and for the measurable features an average and standard deviation were determined. While making the comparisons between the groups, the Student's t-test was used for the features compatible with the normal distribution and evaluated with the Shapiro-Wilk test. If the features were not compatible with this distribution, the U Mann-Whitney test was performed. When analyzing the measurements between two sides, the paired Student's t-test or the Wilcoxon signed-rank test were performed. The correlation factors were calculated as well. In the calculations, the significance level p < 0.05 was considered statistically significant. The calculations were performed by means of the statistical package SPSS.

The subjects consented to the examinations and usage of the obtained results for statistical and research purposes.

Results

The obtained calibers of the vessels are presented in tab. 2. It was shown that the calibers of the vessels decrease with the distance from the heart. However, the caliber of the SFA did not differ in a statistically significant way from the caliber of the PA. The calibers of the PTA and DPA were similar and about 3-times smaller than the caliber of the SFA. The calibers of all vessels examined in the group of men were statistically significantly larger than those in the group of women and the greatest difference was observed between the largest vessels (CFA). No statistically significant differences between the calibers of the right and left sides were determined. It was demonstrated that there are statistically significant correlations between the age and the diameter of the calibers of the examined vessels both in the groups of women and men as well as in the entire group of subjects. With age, the dilatation of the CFA, SFA and PA progressed in the group of women (particularly significant – fig. 1): CFA – r = 0.379, SFA – r = 0.170, PA – r = 0.205, and men. The narrowing of PTA and DPA was also observed (particularly significant in the group of men – fig. 2): PTA – r = -0.229, DPA – r = -0.305. The statistically significant correlations between the following factors were also demonstrated: the height and caliber of CFA (r = 0.509), SFA (r = 0.533), PA (r = 0.438), PTA (r = 0.261), DPA (r = 0.337), the weight and caliber (r = 0.699), SFA (r = 0.646), PA (r = 0.536), PTA (r = 0.299), DPA (r = 0.203) and the BMI and caliber of CFA (r = 0.600), SFA (r = 0.475), PA (r = 0.388), PTA (r = 0.214). As the above mentioned parameters grow, the caliber of the vessels increase.

Tab. 2

The caliber of the examined arteries in the groups of women, men and the entire group (women and men)

Examined vessel	Caliber [mm](average ±SD)
	Women (n = 134)(average ±SD)	Men (n = 94)(average ±SD)	Entire group (n = 228)(average ±SD)
CFA1	7,62±0,96	8,75±0,85	8,05±1,07
SFA2	5,78±0,62	6,50±0,55	6,06±0,69
PA3	5,73±0,67	6,47±0,72	6,03±0,78
PTA4	1,98±0,34	2,16±0,35	2,05±0,36
DPA5	1,85±0,40	2,11±0,43	1,96±0,43

CFA – common femoral artery

SFA – superficial femoral artery

PA – popliteal artery

PTA – posterior tibial artery

DPA – dorsalis pedis artery

Fig. 1

The relation of the caliber of the common femoral artery to the age of the subjects in the group of women

Fig. 2

The relation of the caliber of the dorsalis pedis artery to the age of the subjects in the group of men

Discussion

The measurement of the calibers constitutes an important component of ultrasound examination of the lower extremities. Among others, it allows for a quick and reliable diagnosis of aneurysm, ectasia or hypoplasia of the vessel. In clinical practice, however, the analysis of the morphological image of the vessel usually concentrates on detection of atherosclerotic plaques: their location, size, echogenicity, homogeneity and an estimated degree of artery stenosis. It must be remembered, however, that the decrease in blood flow in the vessel not only results from focal stenosis caused by the atherosclerotic plaques, but sometimes also from the remodeling/shrinking of the whole vessel, in the course of atherosclerosis, hypertension, inflammation or post-radiation changes(. Therefore, the evaluation of the vascular diameter is required even when there are no signs of morphological changes in its lumen. The analysis of the arterial calibers might be particularly useful in monitoring the process of the vascular remodeling.

The paper presents the calibers of the following arteries in the lower extremities: the common femoral artery, superficial femoral artery, popliteal artery, posterior tibial artery and dorsalis pedis artery in healthy subjects. The received results are similar to those obtained by other authors who usually focus on studying selected, single vessels of the femoropopliteal region(.

The authors of this article conclude that the calibers of the arteries in the lower extremities decrease with the distance from the heart, which is also observed in other parts of the body (e.g. upper extremities and head), and that the diameter of the common femoral artery is about three times larger than the diameter of the distal fragment of the crural arteries. This results from the greater muscle mass and greater need for blood in the femoral region than in the lower leg and foot. Nevertheless, no statistically significant differences between the calibers of the superficial femoral artery and popliteal artery were observed despite the fact that the distance between the places where the measurements were taken constituted about 30–40 cm (the caliber of the superficial femoral artery was measured 3 cm below the branching of the common femoral artery, while the caliber of the popliteal artery was measured 3 cm above its branching). Such a result may be explained with the lack of branching on the superficial femoral artery, which functions are merely “to transport”.

In this study, the calibers of all vessels examined in the group of men were statistically significantly larger than those in the group of women. This probably results from significant differences in morphological parameters of the subjects in both groups (tab. 1). Such a reason is also suggested by the statistically significant positive correlations between height, weight and BMI of the subjects and the calibers of the vessels. Similarly to other authors, this study did not present any significant differences in the calibers of the examined arteries between the sides.

Furthermore, the authors noted that with age the calibers of the common femoral artery, superficial femoral artery and popliteal artery increase both in women and in men. The positive correlation between the age of the subject and vascular diameter was also demonstrated by Sandgren et al. in their study concerning the common femoral artery(. This observation may be explained by, among others, structural remodeling of the vascular wall progressing with age: the increase in the relative collagen content and in the collagen/elastin proportion, as well as elastin degradation and the decrease of its, the decrease in the number of nuclei of the smooth muscle cells( as well as mechanical influence of the increased arterial pressure on the vascular wall in the elderly(.

Contrary to the vessels of the femoral region, the calibers of the posterior tibial artery as well as the dorsalis pedis artery decreased with the age of the subject. As of this date, such an observation has not been made in the literature. It seems that the decrease in the diameter of these arteries is caused by their wall structure which is different from the larger vessels described above i.e. lesser amount of elastin and collagen, greater amount of the smooth muscle cells and hypertrophy of the latter(. Nevertheless, in this study the authors were not able to assess the aforementioned processes, for instance, by the evaluation of the intima-media thickness (IMT), since the probe used in the research with the frequency of 7.5 MHz did not allow for a reliable assessment of the crural or pedal arterial walls. The analysis of the wall structure and the complex of the tunica media and intima of the anterior tibial artery in relation to the radial artery was conducted by Osika et al. in their research on the ultrasound microscopy with the use of the probe with the frequency of 55 MHz(.

The omission of the measurement of the fibular artery caliber may constitute a limitation in this research. This vessel, however, is located deeply between the tissues/muscles of the crus which hinders its reliable ultrasound assessment(.

Conclusions

The relation of the caliber of the arteries in the lower extremities to age, sex and morphological parameters reflects the remodeling of the vascular structure which we observe in healthy patients. Being familiar with these processes may enable the differentiation between the physiological changes of the vessel from the pathological ones which occur in the course of atherosclerosis or hypertension.