|Year : 2015 | Volume
| Issue : 4 | Page : 217-222
Clinical and doppler ultrasound evaluation of peripheral arterial diseases in Kano, North-western Nigeria
Anas Ismail, Muhammad Kabir Saleh, Abdulkadir Musa Tabari, Kabiru Isyaku
From the Department of Radiology, Bayero University and Aminu Kano Teaching Hospital, Kano, Nigeria
|Date of Web Publication||14-Jan-2016|
From the Department of Radiology, Bayero University and Aminu Kano Teaching Hospital, Kano
Source of Support: None, Conflict of Interest: None
Aims and Objectives: Doppler ultrasound scan is a non-invasive and cheap tool that complements the roles of computed tomography, magnetic resonance imaging and catheter digital subtraction angiography in the screening, diagnosis and follow up of vascular diseases. In this study, we evaluated and described the findings of the Doppler ultrasound of the peripheral arteries performed at Aminu Kano Teaching Hospital (AKTH), Kano, Nigeria.
Patients and Methods: All the findings of peripheral arterial Doppler ultrasound examinations performed at AKTH during a period of 18 months (from February 2012 to July 2013) were reviewed. All examinations were done using 7.5 MHz linear transducer connected to Mindary Digital Ultrasound Imaging System (Model DC-6; Shenzhen Mindray Biomed Electronics, Shenzhen, China). A 3.5 MHz convex transducer of the same machine was used in obese patients and those with severe subcutaneous oedema.
Results: The findings of 50 males and 28 females were reviewed. Their mean age was 55.8 17.9 years. Diabetic foot disease, intermittent claudication, gangrene and limb swellings were the most common indications for arterial Doppler examination of the lower limbs, constituting 32.1%, 20.5%, 16.7% and 15.4%, respectively. Significant luminal stenosis, total luminal occlusion and loss of arterial resistance were the most frequent findings, constituting 29%, 26.9% and 7.7%, respectively. Femoro-popliteal and below the knee arteries were commonly involved by these abnormalities. Arrhythmia, increased intimal media thickness and wall calcifications were the common compounding findings while diabetes and hypertension were frequently associated clinical problems of these patients.
Conclusion: Doppler ultrasound has a high diagnostic yield in depicting abnormalities in patients with clinical features of peripheral arterial disease.
Keywords: Diabetes, Doppler ultrasound, peripheral arteries
|How to cite this article:|
Ismail A, Saleh MK, Tabari AM, Isyaku K. Clinical and doppler ultrasound evaluation of peripheral arterial diseases in Kano, North-western Nigeria. Niger Postgrad Med J 2015;22:217-22
|How to cite this URL:|
Ismail A, Saleh MK, Tabari AM, Isyaku K. Clinical and doppler ultrasound evaluation of peripheral arterial diseases in Kano, North-western Nigeria. Niger Postgrad Med J [serial online] 2015 [cited 2019 May 23];22:217-22. Available from: http://www.npmj.org/text.asp?2015/22/4/217/173971
| Introduction|| |
Advancing technology in invasive and non-invasive imaging has led to significant improvements in both the diagnosis and treatment of peripheral arterial diseases.  Ultrasound scan is non-invasive and cheap tool for vascular examination of the peripheral arteries. It is currently competing and complementing the roles of computed tomography (CT), magnetic resonance imaging (MRI) and catheter digital subtraction angiography (DSA) in the screening, diagnosis and follow-up of many vascular diseases.  Compared to DSA, duplex imaging was able to detect arterial disease with an overall sensitivity of 92%, specificity of 99%, positive predictive value of 91% and negative predictive value of 100%.  In addition to determination of structural anatomic lesion, application of Doppler modes allows determination of functional status of the vessels by measuring flow velocities and extent of vascular compliance.  Furthermore, it indirectly assesses the heart rate and rhythm through continuous quantitative and qualitative recording of the blood flow dynamics of the peripheral artery.
Symptoms of peripheral artery disease are becoming more important due to rising incidence of the disease and the risk factors (such as diabetes, hyperlipidaemias, smoking and sedentary lifestyles). As a result of limited availability of highly specific diagnostic tools such as CT, MRI and DSA in many developing economies, ultrasound is gaining importance. 
Therefore, this early experience describes the spectrum of abnormalities detectable by ultrasound examination of the peripheral arteries at Aminu Kano Teaching Hospital (AKTH), Kano, Nigeria. We also analysed the clinical presentation of the patients with their corresponding findings on Doppler sonography.
| Patients and Methods|| |
This study was conducted at the vascular ultrasound clinic of AKTH from February 2012 to July 2013. Following ethical clearance for the conduct of this work (reference number: NHREC/21/08/2008/AKTH/EC/1225). The records of the socio-demographic characteristics of the patients, the clinical symptoms and risk factor(s) for the development of peripheral arterial disease, site of the examination and the source of the patients were documented on the data collection instrument. For the purpose of this study, those older than 65 years were considered as elderly.
Thereafter, examination of the relevant limb (whether upper or lower; right or left) were done with the patient lying supine or prone (depending on the specific artery) using 7.5 MHz linear transducer connected to Mindary Digital Ultrasound Imaging System (Model DC-6; Shenzhen Mindray Biomed Electronics, Shenzhen, China). Occasionally, 3.5 MHz convex transducer of the same machine was used (to optimise the depth) in obese patients and those with severe subcutaneous oedema. Following application of water soluble gel, ultrasound scan was started with grey scale mode to demonstrate clarity (or otherwise) of the lumen, intimal media thickness (IMT) and the presence (or absence) of calcifications. Colour with or without power Doppler scans were done on the arteries to document the presence and direction of blood flow. Spectral Doppler measurements were done on each of the major arteries, obtained following application of angle-corrected sampling gate at the centre of the colour map of the artery. Furthermore, lowest possible filter, highest gain below noise level and the smallest scale were selected to avoid aliasing. The height of the Doppler waveforms was maximised to facilitate measurement. After obtaining contiguous spectral tracings for at least five cardiac cycles, automatic velocity measurements of the peak systolic velocity (PSV) end diastolic velocity and corresponding resistive indices were obtained using in-built electronic callipers. The scan was considered normal if the artery showed normal calliper, IMT of 1 mm (or less), uniform colour flow and consistent typical triphasic appearance of the waveform. The artery was considered to have a haemodynamically significant stenosis in the presence of either (or combination) of the following: Luminal diameter reduction by at least 50%, sudden marked increase in PSV (of more than 100% of the expected) at the area of narrowing and presence of "parvus tardus" pattern in the distal run-off arteries as illustrated in [Figure 1]. The artery was considered to be totally occluded if there was no demonstrable blood flow with power Doppler mode.
|Figure 1: Duplex Doppler ultrasound scan (using power Doppler protocol) of the right dorsalis pedis artery, showing dwarf systolic peak (velocity of 12.03 cm/s), spectral broadening and significant diastolic blood flow (end diastolic velocity of 7.83 cm/s)|
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The examination was also extended to the external iliac arteries. In addition, complimentary corresponding venous examinations were conducted on each limb to detect asymptomatic incidental abnormalities such as deep venous thrombosis. All examinations were performed (by, at least, a consultant radiologist) with patients lying calmly on the examination table and each examination was conducted over a minimum of 20 min. Data analysis was conducted using Statistical Package for Social Sciences version 16.0 (SPSS Inc., Chicago IL.) for windows.
| Results|| |
Distribution of vascular ultrasound examinations at Aminu Kano Teaching Hospital
During the review period, a total of 459 scans were conducted in the clinic. [Table 1] shows the specific requests for peripheral examination in 78 patients, making up 17% of all vascular ultrasound examinations and these constitute the sample of this study. Others include 99 obstetric scans (21.6%), 30 carotid (6.5%), 37 renal scans (8.1%), 50 scrotal/testicular (10.9%), 70 transcranial (15.2%), 15 portal/hepatic vascular scan (3.3%) and 80 peripheral venous scan (17.4%).
|Table 1: The distribution of vascular ultrasound examinations in Aminu Kano Teaching Hospital|
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Demographic and clinical characteristics of the patients
Their ages ranged from 4 to 90 years, with a mean of 55.8 (±17.9). They consist of 50 males (64.1%) and 28 females (35.9%). Out of these patients, 70 had lower limb examination while eight had upper limb arterial examinations. As shown in [Table 2], the frequent indications include diabetic foot syndrome 25 (32.1%), intermittent claudication 16 (20.5%), limb swelling 12 (15.4%), gangrene 13 (16.7%) and limb pain and swelling 4 (5.1%). Others include trauma and a clinical suspicion of peripheral vascular disease.
[Table 3] shows additional compounding factors of vascular disease in these patients which include diabetes 35 (44.9%), hypertension 18 (23.1%), old age 7 (9.0%), trauma 1 (1.3%); while 14 (17.9%) patients did not show obvious clinical risk factor.
|Table 3: The compounding clinical history for peripheral vascular disease in these patients|
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Doppler ultrasound findings
The findings of the arterial Doppler examination are shown in [Table 4]. It revealed 10 normal scans (12.8%), 11 patients with increased IMT (14.1%), 23 patients with haemodynamically significant luminal stenosis (29.5%), 21 with total luminal occlusion (26.9%), six with loss of arterial resistance (7.7%). Other findings include arterio-venous malformation (AVM), intra-luminal foreign body and aneurysmal dilatation. These collectively constituted 9%.
The territorial arterial involvements are illustrated in [Table 5]. Femoro-popliteal 21 (26.9%), multiple below-knee arteries 14 (17.9%), posterior tibial artery 8 (10.3%), each of the sub-clavian, anterior tibial and dorsalis pedis arteries have a frequency of 4 (5.2%). Other less commonly involved arterial territories include ilio-femoral (2.6%), radial and peroneal arteries. Out of these, 29 cases are on the right (37.2%), 24 cases on the left (30.8%) while the remaining 25 cases have bilateral lesions (32.0%).
In addition to these specific findings, incidental findings include 28 cases of increased IMT in the iliac arteries (35.9%), 12 cases of arterial wall calcification (15.4%), 11 cases of arrhythmias (14.1%), four cases of venous thrombosis (5.1%) while 21 patients did not show additional incidental findings (26.9%).
The gender distribution of Doppler findings revealed the presence of lower extremity peripheral artery disease (LEAD) in 41 males and in 20 females, giving the male:female ratio of 2.05:1. However, this difference is not statistically significant (χ2 = 1.151, df = 1, P > 0.05).
Doppler ultrasound findings in diabetic patients
Out of 25 patients with diabetic foot syndrome, 10 had total arterial occlusion (40%), seven had haemodynamically significant stenosis (28%) and three had loss of peripheral resistance (12%). Only 1 (4%) person had a normal scan. They also showed additional incidental findings of increased IMT in other arteries (13 cases) and inconsistent waveforms due to arrhythmia (five cases).
Doppler ultrasound findings in patients with intermittent claudication and limb swelling
Out of 16 patients with intermittent claudication, 9 (56.25%) had haemodynamically significant stenosis, 2 (12.50%) had increased IMT while 4 (25.00%) cases had arrhythmia. Only 1 (6.25) patient had a normal scan in this group.
Out of the 13 patients with limb swelling, 5 (38.5%) had increased IMT, 3 (23.1%) had a normal scan and 2 (15.3%) had AVM. Around 3 (23.1%) cases of arterial wall calcifications were also noted in this group.
Laterality of the lesion in relation to the clinical presentation
Diabetic foot syndrome was more common on the right (46.2%) than the left (19.2%) while gangrene was more often bilateral (42.9%) than unilateral (28.6% on the right and also on the left). The side predilections of abnormalities in other patients are shown in [Table 6].
|Table 6: The distribution the relationship between the laterality of the lesion with the clinical presentation|
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Relationship between risk factors for vascular disease and compounding ultrasound findings
Fifty-two cases of incidental findings were discovered in this review. Out of these, diabetes had the highest frequency of compounding ultrasound findings of vascular wall calcification, arrhythmias and increased IMT; encountered in 51.9%. This was followed by hypertension, showing incidental findings in 32.7% of cases. The details of these relationships and those with other risk factors are shown in [Table 7]. For further illustration, [Figure 2] shows a spectral Doppler sonogram of a 75-year-old diabetic with spectral broadening of the superficial femoral artery and inconsistent cardiac cycles due to associated arrhythmias. In addition, a case of traumatic pseudoaneurysm (showing severe turbulence of blood flow with mosaic colour appearance) was encountered and exemplified in [Figure 3].
|Figure 2: Spectral Doppler sonogram of the right superficial femoral artery in a diabetic patient, showing continuous diastolic forward flow and inconsistent systolic peaks of the cardiac cycle form associated arrhythmia|
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|Figure 3: A colour Doppler sonogram of a 25-year-old man with post-traumatic pseudoaneurysm of the superficial femoral artery. Note the neck of the aneurysmal sac (arrows)|
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|Table 7: Relationship between the incidental ultrasound findings and the risk factors for vascular disease|
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| Discussion|| |
Doppler sonography is a well-accepted non-invasive imaging modality to be used as a diagnostic test for detecting and grading the presence and severity of arterial disease. This preliminary data revealed a relatively busy vascular ultrasound clinic with a turnover close to 500 patients per annum. The examination of the peripheral arteries is very common in our institution, making up 17% of all vascular ultrasound examinations.
The mean age of 55.7 years in these patients corresponds to the typical patients with peripheral arterial disease. This is as demonstrated by Shaheen and Sohail  in their review of 100 diabetics with peripheral arterial disease. Ascher et al.  also documented the mean age of 55 years in their review of 68 patients with acute lower limb arterial ischaemia in Pakistan. As shown in this review, the relative high frequency of diabetic foot disease, intermittent claudication and frank gangrene underscores the magnitude of these problems in the arena of peripheral vascular disease in our environment. This was illustrated by Odenigbo et al.,  in their prospective study of hypertensive patients, showing the overall prevalence of peripheral artery disease to be 24.8% in Nnewi, South-Western Nigeria.
Doppler evidence of vascular abnormality was found in 87.2% of our patients with clinical suspicion of peripheral artery disease (while 12.8% were normal). This is higher than 62% reported by Shaheen and Sohail.  Though their sample size was relatively larger (100 compared to 78 in this study), this disparity may be from differences in the experiences of the radiologists may also increase the sensitivity of ultrasound results as well as differences in the characteristics of the study subjects. On the other hand, this disparity may imply a possible higher prevalence of peripheral vascular disease in our local environment compared to theirs.
Our study showed no statistically significant gender difference in the prevalence of sonographic evidence of LEAD. This is at variance with the findings of Sadrzadeh Rafie et al.  in their review on 1561 patients undergoing coronary catheterisation; where they found higher incidence of LEAD in females compared to their male counterparts. However, our findings agree with those of Collins et al.  in their study on gender and peripheral artery disease. Though they did not use Doppler ultrasound in their research, they found no significant differences by gender in the prevalence of LEAD. Similarly, their assessment of risk factors showed no gender disparity.
This review also showed 29.5% of the patients had significant luminal stenosis while 26.9% of them showed complete stenosis. These implied a relatively high frequency of severe LEAD in these groups of patients. This is in conformity with high prevalence of LEAD, affecting about 20% of adults older than 55 years to an estimated total of 27 million people in the Western World.  The additional compounding ultrasound findings of increased IMT in the iliac arteries on extended examination, arterial wall calcification, arrhythmias and venous thrombosis imply great potential for co-morbidities in these patients.
As shown in our results, the frequency of disease involvement of femoro-popliteal was 26.9%, multiple below-knee arteries 17.9%, and posterior tibial artery 10.3%. This pattern slightly differs from the report of Guo et al.  on 162 diabetics with arterial lesions. They found frequencies of anterior (92/127, 67.2%) and posterior tibial arteries (91/124, 73.4%), which was higher than that in iliac artery (8/33, 24.2%), popliteal artery (53/157, 33.8%) and femoral artery (11/78, 14.1%). Nevertheless, their study uses diagnostic DSA while this study was done with Doppler ultrasound.
The findings of 10 diabetics with total arterial occlusion, seven with haemodynamically significant stenosis and three with loss of peripheral resistance illustrates the magnitude of diabetes in the pathogenesis of LEAD in general. The loss of peripheral arterial resistance could have been a marker of chronic inflammation and injury to the arterial wall in the peripheral or coronary vascular system, which is a precursor for atherosclerotic changes and macroangiopathy.  In this regard, Umuerri and Obasohan  found a prevalence of lower limb LEAD at 35.6% of the 380 diabetics using Doppler ankle-brachial index (ABI) <0.9 in Benin City, Nigeria. On the other hand, Framingham Heart Study  revealed that 20% of symptomatic patients with LEAD had diabetes. Nevertheless, this may still underestimate the prevalence, given that many more people with LEAD are more often asymptomatic. Furthermore, over half of those with PAD are asymptomatic or have atypical symptoms, about one-third have claudication and the remainder has more severe forms of the disease.  In addition, there is a more rapid progression in diabetic patients with 11 times higher rate of major lower limb amputation compared to non-diabetics and a doubling of the 5-year mortality. 
The emphasis on diabetes in LEAD was necessitated by the fact that LEAD is an important contributor to diabetic foot ulceration and gangrene leading to lower extremity amputation in diabetes mellitus. , These diabetic patients also showed additional compounding findings of increased IMT in other arteries (25%) and inconsistent waveforms due to arrhythmia (9.6%). Furthermore, diabetic foot syndrome is more common on the right (46.2%) than the left (19.2%) while gangrene is more often bilateral than unilateral. Similar right-sided predominance was also reported by Coxon and Gallen  in their review of 2000 patients who had amputations from diabetic foot syndrome.
Our findings also showed a considerable contribution of hypertension among the risk factors for LEAD. Similarly, Martha et al.  also found high association between hypertension and LEAD using Doppler ultrasound and ABI, they found evidence of LEAD in 41.8% of hypertensive patients and majority of which were asymptomatic. Therefore, reliance on symptoms alone could underestimate LEAD.
The high percentage of significant luminal stenosis in claudicating patients showed the relative high sensitivity of Doppler ultrasound in detecting the arterial lesions. As illustrated by Aly et al.,  duplex imaging can detect arterial disease with an overall sensitivity of 92%, specificity of 99%, positive predictive value of 91% and negative predictive value of 100% when compared with DSA.
| Conclusion|| |
This preliminary review of 78 patients showed high frequency of femoro-popliteal and tibial arterial involvement in LEAD. In addition, arrhythmia, increased IMT and arterial wall calcifications were the common incidental findings while diabetes, hypertension and old age were frequently associated clinical problems of these patients. Our study showed high diagnostic yield of Doppler ultrasound in depicting abnormalities in patients with clinical features of peripheral arterial disease.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]