Impact of Diabetes Mellitus and Ischaemic Heart Disease on the Blood Resistivity Index of Renal Arteries in Hypertensive Patients
Moawia Gameraddin1, Walaa Hidirbi2, Suzan Abdelmaboud3, Abdulaziz Qurashi4, Sultan Alshoabi5
1 Associate Professor, Department of Diagnostic Radiologic Technology, Taibah University, Almadinah, Saudi Arabia.
2 Assistant Professor, College of Radiological Sciences and Medical Imaging, Alzaiem Alzhari University, Khartoum-Sudan, Khartoum, Sudan.
3 Assistant Professor, College of Radiological Sciences and Medical Imaging, Alzaiem Alzhari University, Khartoum-Sudan, Khartoum, Sudan.
4 Associate Professor, Department of Diagnostic Radiologic Technology, Taibah University, Almadinah, Saudi Arabia.
5 Associate Professor, Department of Diagnostic Radiologic Technology, Taibah University, Almadinah, Saudi Arabia.
NAME, ADDRESS, E-MAIL ID OF THE CORRESPONDING AUTHOR: Dr. Moawia Gameraddin, Taibah University, Almadinah, KSA. P.O. 3001, Almadinah Amunawarah, Saudi Arabia.
E-mail: m.bushra@yahoo.com
Introduction
Hypertension (HTN) is considered as one of the most common health problems. Doppler sonography plays an effective role in haemodynamic assessment of renal arteries in patients with essential HTN.
Aim
To assess renal vascular Resistive Index (RI) in patients with essential HTN in co-existence with Diabetes Mellitus (DM) and Ischaemic Heart Disease (IHD).
Materials and Methods
This was a cross-divtional study which involved 100 hypertensive patients selected by a simple, convenient sampling method from June 2014 to August 2016. The participants were categorised into four groups; 55 patients with controlled HTN while the uncontrolled HTN groups included 20 with HTN coupled with DM, 18 with HTN and IHD, and seven patients of HTN accompanied by both DM and IHD. The patients were investigated using Duplex Doppler ultrasonography to assess the RI of the renal arteries. Analysis of variance and Student’s t-test were performed to compare renal RI values between controlled and uncontrolled hypertensives.
Results
The mean renal RI in patients with controlled HTN was 0.59±0.093, 0.71±0.035 in DM, 0.70±0.029 in IHD, and 0.72±0.029 in patients with IHD and DM. Controlled hypertension revealed a stable blood RI across the renal arteries (RI=0.59±0.093). The renal RI was significantly higher in patients with DM, IHD and DM+IHD group compared to patients with controlled HTN (p-values=0.004, 0.014 and 0.001).
Conclusion
The renal RI is an important parameter which provides useful information about haemodynamics of renal arteries in essential HTN complicated with DM and IHD.
Introduction
HTN is one of the most common health related problems and it affects more than 100 million people worldwide. It leads to cardiovascular end-organ damage, which leads to increased morbidity and mortality that is related to high costs to the community, thus making a significant public health challenge [1]. Ultrasound Doppler plays a significant role in the diagnosis of acute or chronic nephropathies and nephrovascular disease, as well as predicts early renal damage in hypertensive patients [2]. Ultrasound imaging is a non-invasive, widely available, and accepted imaging modality that provides reasonably accurate images about the structural changes within the kidney [3]. The Doppler RI has been utilised for many years in the assessment of a variety of renal diseases such as renal artery stenosis, risk progression in chronic kidney disease and to differentiate acute from chronic obstructive renal disorders. Recently, renal RI is considered as a predictor marker of renal histological damage and a prognostic indicator [4]. More recently, evidence has shown that an increased renal RI, not only reflects the changes in renal blood supply but is also found to correlate with systemic haemodynamics and the presence of atherosclerosis. This relationship may provide useful clinical information in patients affected with primary HTN [5]. Therefore, renal RI has been recommended to evaluate patients with primary HTN and signs of renal disorders.
DM and IHD have an increased risk for kidney disease. There is a close correlation between HTN and DM with Cardiovascular Disease (CVD), which is responsible for the leading cause of morbidity and mortality [6]. Therefore, in these situations, renal RI will play a vital role in characterising haemodynamic significance, which provides useful information in prognosis and management. The present study explores the impact of DM and IHD on the haemodynamics of the renal arteries in hypertensive patients. The study would demonstrate, how much IHD and DM change, the RI in HTN. One of the previous studies had demonstrated renal RI in HTN alone without other complications such as CVD [7]. Furthermore, no studies have found to demonstrate the impact of IHD on the blood RI of the renal arteries in hypertensive patients. The study aimed to evaluate the significance of renal RI in hypertensive patients with co-morbidity of DM and IHD.
Materials and Methods
This was a prospective, cross-sectional study performed at Khartoum State hospitals, namely in Soba University Hospital, Sharq El-Niel, Khartoum North, and Umdorman Military Hospital, Sudan from June 2014 to August 2016. IEC approval has been applied for the present study and the study was judged to be having less than minimal risk. Hundred Sudanese participants diagnosed with essential HTN documented in their records were selected by the method of simple, convenient sampling and obtaining informed consent. The participants were categorised into four groups; 55 patients with controlled HTN while the uncontrolled HTN groups included 20 with HTN coupled with DM, 18 with HTN and IHD, and seven patients of HTN accompanied by both DM and IHD. The uncontrolled DM was defined as those patients who were not regular on diabetes medicines and did not follow the meal plan or the instructions. Patients with IHD were those with cardiac problems caused by narrowed coronary arteries [8]. On the other hand, controlled hypertension was defined as blood pressure below 140/90 mm Hg or, if the participant had diabetes or chronic renal disease, below 130/80 mm Hg, while uncontrolled HTN was defined as a blood pressure ≥140/90 mm Hg [9]. The clinical data was taken from the patients’ records. The patients were investigated with Doppler ultrasound to assess the renal RI. The exclusion criteria were pregnant, previous history of renal surgery, and atrophy of kidneys.
Doppler sonographic investigation was performed using Toshiba Nemio 20 (Toshiba, Japan) and Mindray DC-N3 (Mindray, China). A 3.5 MHz curvilinear array transducer with a variable focal zone was used. Patients were fastened for three hours to get rid of gases and then examined in supine positions, following the renal ultrasound protocols. The patients were scanned in the supine and oblique positions. Each kidney was examined with a B-mode ultrasound in at least two planes to maintain the renal length for each kidney. The average length of the kidneys was considered 8.5 up to 12 cm; renal length lesser than 7 cm was considered a small kidney. The RI was measured at the interlobular or arcuate artery in the upper, middle, and lower portions of the kidney and the mean values were calculated for each kidney. The renal RI values > 0.70 were considered high [10].
Statistical Analysis
Data entered and analysed by utilising the Statistical Package for the Social Sciences (SPSS), version 23. Descriptive statistics used Mean±Standard Deviation (SD). Pearson’s correlation was used to find a relationship of renal RI with the sonographic findings and characteristics of the participants. Analysis of Variance (ANOVA) test was used to compare the mean RI values of the controlled hypertensive with DM and IHD. The significant statistical value was p<0.05.
Results
Out of the 100 involved patients, the average age was 40.4±5 years, and the duration of HTN was 7.72±3 years. In controlled group of HTN, the number of males was 35 and 20 females, while in the uncontrolled group, there were 16 males and 29 females.
The mean renal RI was significantly associated with patient age, gender, and duration of HTN, and renal length. The mean renal RI was considerably higher in females than males. There was a significant negative correlation between renal RI and renal length (p-values=0.02 and 0.009 for lengths of the right and left kidneys, respectively). The negative correlation indicated that the renal RI increased as renal length decreased [Table/Fig-1]. The renal RI was estimated in the age groups, and it was observed that it was significantly different among the groups (p-value <0.001). The age group 41-70 years revealed a higher incidence of HTN and elevated RI compared to the other groups [Table/Fig-2].
Correlation of the renal RI with demographic data of the participants and renal length.
| Characteristics and findings | Mean±SD | Correlation coefficient (r) | p-values |
|---|
| Age (in yrs.) | 40.4±5 | 0.23 | <0.001 |
| Duration of HTN (in yrs) | 7.72±3 | 0.32 | <0.001 |
| Male (n=51) | RI=0.60±0.092 | 0.34 | <0.001 |
| Female (n=49) | RI=0.65±0.047 |
| Length of the right kidney (cm) | 8.9850±1.01 | -0.18 | 0.02 |
| Length of the left kidney (cm) | 9.4760±0.98 | -0.20 | 0.009 |
SD: Standard deviation; RI: Resistive index. Pearson correlation was used to find the correlations
Comparison of mean renal RI value in age groups of the participants.
| Age groups | Frequency | RI values Mean±SD | Significance between groups |
|---|
| <20 years | 22 | 0.62±0.045 | <0.001 |
| 20-40 years | 30 | 0.57±0.11 |
| 41-70 years | 41 | 0.66±0.033 |
| >70 years | 7 | 0.63±0.019 |
| Total | 100 | 0.62±0.077 |
ANOVA test was applied to compare between the groups
The mean renal RI was 0.59±0.093, 0.71±0.035, 0.70±0.029, and 0.72±0.029 in controlled HTN patients group, HTN with DM, HTN with IHD, and in both DM and IHD groups, respectively. The mean renal RI was significantly elevated in DM and IHD more than the controlled hypertension group [Table/Fig-3].
Comparison of the mean RI values in controlled HTN with DM and IHD.
| Groups of hypertension | Frequency | Mean RI values ±SD | Controlled hypertension (mean RI values ±SD) | p-values | 95% confidence interval |
|---|
| DM | 20 | 0.71±0.035 | 0.59±0.093 | 0.004 | 0.018–0.127 |
| IHD | 18 | 0.70±0.029 | 0.59±0.093 | 0.014 | -0.123–0.010 |
| DM and IHD | 7 | 0.72±0.029 | 0.59±0.093 | 0.001 | -0.148–-0.082 |
RI: Resistive index, SD: Standard deviation, DM: Diabetes mellitus, IHD: Ischaemic heart disease
Student’s t-test was used to compare each group of uncontrolled hypertension with the controlled group
Discussion
HTN is a significant risk factor affecting the renal artery RI. The present study explored the impact of DM and IHD on renal RI in hypertensive patients. In this study, renal RI was high in hypertensive patients. Furthermore, it was noted that HTN with diabetes had increased renal RI more than HTN alone. In agreement with the present study findings, Mancini M et al., reported a significant elevation of renal RI in Type 2 diabetic patients (RI=0.70±0.05) [11]. On the other hand, Andrikou I et al., reported a significant increase in renal RI in patients with essential HTN [12]. Similarly, Ohta Y et al., reported that RI was significantly increased in diabetic nephropathy [13]. Several studies have demonstrated the elevation of renal RI due to the impact of DM, which changes vascular resistance in the kidneys [14-16]. The elevation of renal RI is attributed to diabetic nephropathy. Viazzi F et al., reported that high renal RI was used as a predictor for renal damage in primary HTN is a risk factor for renal impairment [5]. The effect of IHD on renal RI was not demonstrated in the recent literature. The present study found that renal RI was high in hypertensive patients with IHD (0.70±.029), but lesser than those with DM. Consistent with this result, Komuro K et al., reported a significant elevation of renal RI in CVD [17]. The increased RI was attributed to changes in vascular compliance or because of change in a small renal vessel. Besides, blood pressure and heart rate were essential determinants of RI [18].
In this study, high values of renal RI were observed in diabetic patients. Similarly, Hamano K et al., studied the association of renal RI in type 2 diabetic patients [19]. They reported that renal RI was significantly high in diabetic patients compared to the normal ones. However, in previous studies, RI >0.8 was proven to be a significant deterioration in the Glomerular Filtration Rate (GFR) [20]. Thus, increased renal RI is useful to assess renal function in type 2 diabetes with microalbuminuria. In the current study, significant positive correlations were found between RI and gender and age (p-values <0.001). Recent studies have demonstrated that the RI correlates with age and gender [21,22]. In agreement with present study findings, Toledo C et al., reported that older age and female sex are associated with renal RI ≥0.70 [23]. Therefore, age and gender were independent factors that influenced the renal RI.
Limitation(s)
The study faced significant problems that the sample size was not large enough. Secondly, we see it challenging to find an increased number of patients with IHD.
Conclusion(s)
DM and IHD caused considerable elevation of renal RI in hypertensive patients. This elevation reflects the progression of renal diseases. The assessment of renal RI may have implications on the planning of HTN treatment. Further studies are recommended to confirm the initial results of the present study.
SD: Standard deviation; RI: Resistive index. Pearson correlation was used to find the correlationsANOVA test was applied to compare between the groupsRI: Resistive index, SD: Standard deviation, DM: Diabetes mellitus, IHD: Ischaemic heart diseaseStudent’s t-test was used to compare each group of uncontrolled hypertension with the controlled group
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