|Year : 2018 | Volume
| Issue : 1 | Page : 17-23
Comparative sonographic assessment of renal dimensions and clinicobiochemical parameters among diabetic and nondiabetic adults in Benin City, Nigeria
Emilomo O John1, Blessing O.-E Igbinedion2, Adenike O Akhigbe2
1 Radiology Department, University of Benin Teaching Hospital, Benin, Edo, Nigeria
2 Radiology Department, College of Medical Sciences, University of Benin, Benin, Edo, Nigeria
|Date of Web Publication||29-May-2018|
Dr. Blessing O.-E Igbinedion
Radiology Department, College of Medical Sciences, University of Benin, Benin, Edo
Source of Support: None, Conflict of Interest: None
Background: Diabetes mellitus affects all major organs of the body including the kidneys. One of its effects on the kidney is alteration of renal volume.
Aim: The aim of this study was to sonographically evaluate and compare the renal volume in patients with diabetes and nondiabetic controls. This study also correlated the effect of biochemical and anthropometric measurements with the renal volume.
Materials and Methods: The study is prospective, comparative, and cross-sectional involving ultrasonic measurement of renal dimensions of 150 adults with diabetes and 150 nondiabetic adults at the University of Benin Teaching Hospital, Benin City, using a Sonace X6 ultrasound machine (Medison Inc., Seoul, South Korea). The anthropometric measurements and biochemical estimation of fasting blood sugar, glycosylated hemoglobin, plasma creatinine, and urinary protein were performed.
Results: The right and average renal volumes were higher in the diabetics than that in the nondiabetics. The left renal volume, although higher in diabetics, was, however, not statistically significant (P = 0.219). The renal volumes (right, left, and average) showed positive correlation with height, weight, and body mass index for the group of adults with diabetes and the nondiabetic groups. The renal volumes also correlated negatively with a duration of diabetes at significant statistical levels (r = −0.453, P = 0.012; r = −0.424, P = 0.020; r = −0.404, P = 0.027 for right, left, and average kidney volumes, respectively).
Conclusion: Renal changes in diabetics that affect its dimensions are demonstrable sonographically. Hence, ultrasound plays some role in monitoring diabetics.
Keywords: Diabetes mellitus, diabetics, renal dimensions, renal volume, sonographic
|How to cite this article:|
John EO, Igbinedion BO, Akhigbe AO. Comparative sonographic assessment of renal dimensions and clinicobiochemical parameters among diabetic and nondiabetic adults in Benin City, Nigeria. J Med Trop 2018;20:17-23
|How to cite this URL:|
John EO, Igbinedion BO, Akhigbe AO. Comparative sonographic assessment of renal dimensions and clinicobiochemical parameters among diabetic and nondiabetic adults in Benin City, Nigeria. J Med Trop [serial online] 2018 [cited 2018 Jun 20];20:17-23. Available from: http://www.jmedtropics.org/text.asp?2018/20/1/17/233422
| Introduction|| |
The burden of increased morbidity and mortality from diabetes mellitus (DM) is heavier on developing countries because of rapid urbanization, nutritional transition, and increasing sedentary lifestyles. DM has also grown in parallel with the worldwide rise in obesity. The pandemic is still a leading killer disease in the sub-Saharan Africa, with a facility-based survey identifying a high mortality rate of about one-third (32.5%) of admitted cases dying within ten years of diagnosis. Current estimated prevalence of DM in Nigeria is 5% and its complications present an immense public health burden, which makes it important to study its effect on the kidneys. In Nigeria, poor glycemic control is one major factor that complicates DM. Poor, inadequate detection, and management of DM especially in resource poor settings due to the ineffective healthcare system increases the risk of suffering complications, which can cause chronic renal failure (a prime indication for dialysis).
Diabetic nephropathy is a micro-vascular complication of diabetes, and it diminishes renal functions. In addition, diabetic nephropathy is a common pathology among people with diabetes with a prevalence of over 40%. Schmitz et al. put the prevalence of diabetic nephropathy for type 1 DM at 40%, while Alrawahi et al. found it to be at 42.5% in the population they studied. Fortunately, disease progression may be evaluated with the use of renal ultrasonography to monitor changes in the size of the kidneys. Patients with type 1 DM are at a higher individual risk of nephropathy; however, type 2 DM is more common and generally will have more patients presenting with nephropathy as compared to type 1 DM.
End-stage renal failure following diabetic nephropathy is still the leading cause of death among patients with diabetes. In the early stage of diabetic nephropathy, the arteriolar vasoconstriction increases glomerular pressure causing glomerular hypertension leading to hyper-filtration-induced nephromegaly. In the later stage of the disease, however, the progressive damage of the kidney from glomerular sclerosis and tubular ischemia results in the shrinkage of the kidneys and reduction in its functionality.
The determination of kidney size is important, because it can help in the detection of renal abnormalities and predict renal function. Renal ultrasound typically assesses kidney size, parenchymal echogenicity, rule out obstruction, as well as measures parenchymal resistive index using Doppler. Varying degrees of accuracy of evaluation of renal volume have been obtained using X-rays, magnetic resonance imaging (MRI), computerized tomography, scintigraphy and excretory urography., However, apart from MRI (which is expensive and relatively unavailable), the others are associated with risks of ionizing radiation; hence, these may not be suitable for regular patients’ follow-up. The use of contrasts agents with its attendant potential complications count also against the use of these imaging modalities.
The hypothesis for this study is that there is no difference in renal dimensions between patients with diabetes and “normal” persons even when correlated with anthropometric and biochemical parameters. Therefore, the aim of this study is to compare renal volume in diabetics with that of persons with nondiabetics on ultrasonography, and also to correlate the findings with biochemical and anthropometric measurements of the subjects. This study may augment the care of diabetics and provide baseline values that will alert the clinician on the possibility of deranged renal function and need for renal transplant.
| Materials and methods|| |
This was a prospective comparative cross-sectional descriptive sonographic study of renal volume among 150 confirmed diabetic and 150 nondiabetic (controls) adults. The study was conducted over a period of six months from September 2015 to March 2016 at the ultrasound unit of the Department of Radiology, University of Benin Teaching Hospital (UBTH).
Written informed consent was obtained from the subjects after adequate explanation of the objectives as well as the risks and benefits of the study. Approval for this study was granted by the Ethics and Research Committee of UBTH.
Inclusion criteria for the diabetics group include confirmed cases of adult diabetics who were aged between 18 and 70 years, while exclusion criteria were subjects with end-stage renal failure, diabetics less than 18 years or above 70 years of age, and participants with ectopic kidneys/other congenital anomalies of the kidneys. In contrast, inclusion criteria for the controls were nondiabetic and age between 18 and 70 years. Exclusion criteria for the controls were adults with history of deranged blood glucose, or renal pathology confirmed by albuminuria; age below 18 or above 70 years; history of hypertension; pregnant women; and participants with ectopic kidneys/congenital anomalies.
The relevant medical history and physical examination findings were entered into the questionnaire. Drug history was obtained to ensure that subjects were not on drugs such as cephalosporins or quanidines. They were also assessed to ensure that they did not suffer for jaundice, because high bilirubin and ketone levels in the above groups can alter creatinine assay. All the patients biodata details such as height, weight, and body mass index (BMI) were measured/calculated.
The study was performed early in the morning to get an appreciable fasted number, which was useful for the fasting blood sugar (FBS) evaluation. Blood samples were obtained from the thumb pulp of the control subjects following a needle prick, and their FBS level were determined using calibrated test strips of an ACCU-CHEK glucometer (Roche, Mannheim, Germany), while urine samples were taken for urinalysis using Combur Test stripes (Roche, Mannheim, Germany). For diabetics, blood and urine samples were collected for biochemical estimation of plasma creatinine levels, HbA1c, FBS, as well as micro-albumin levels and delivered to the laboratory for analysis.
The scans were taken in supine or prone position using an ultrasound machine, Sonace X6 (Medison Inc., Seoul, South Korea) with a 2–8 MHz variable frequency curvilinear transducer. The right and left kidneys were scanned in longitudinal, transverse, and oblique planes with measurements of the renal length, width, and thickness performed. The kidney volume was obtained using the prolate ellipsoid formula (inbuilt in the ultrasound machine software):
Data analysis was performed using the Statistical Package for the Social Sciences for windows version 20.0 (SPSS Inc., Chicago, IL, USA) software. Statistical test of significance was conducted using Pearson correlation analysis, chi-square test for categorical data, Student t-test, and analysis of variation where applicable. At 95% confidence interval (CI), two-tailed P-values less than or equal to 0.05 was considered statistically significant.
| Result|| |
A total of 300 persons participated in the study made up of 150 persons with diabetes and 150 persons without diabetes. There was no significant difference in the mean ages between the study participants and controls (P = 0.554). More males were in the diabetic group (72.7%) than in the control group (67.3%) without significant difference in the sex distribution of the study participants (χ2 = 1.587; P = 0.208) − [Table 1].
|Table 1: Demographic, anthropometric, clinical, and biochemical variables of the study population|
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The mean ± standard deviation (SD) of the anthropometric indices and blood pressure measurements of the study participants are presented in [Table 1]. Though the diabetic participants had a higher weight and BMI, there was no significant difference in the weight, height, and BMI between the diabetic population and the controls (P = 0.173, 0.980, and 0.075, respectively). Similarly no significant difference was found in the systolic, diastolic and mean arterial pressures of the diabetic participants and the controls (P = 0.959, 0.202, and 0.462, respectively).
Majority of the participants had type 2 DM (80.7%). The average duration of illness in the diabetic group was 10.2 ± 7.2 years. Forty-six (30.7%) of the participants with diabetics had the disease for <5 years, while 13 (18.7%) for over 20 years [Table 1]. The average FBS of the diabetics was 144.7 ± 67.8 mg/dL, while it was 89.3 ± 10.0 for the participants without diabetes, and the difference was statistically significant, P ≤ 0.001. The mean glycated hemoglobin concentration was 9.5 ± 3.0%, mean creatinine was 2.0 ± 1.7 mg/dL, and urinary albumin concentration for the diabetics was 6.0 ± 1.0 g/dL and 3.5 ± 1.3 g/dL for the nondiabetics − [Table 1].
The right kidney length, width, and volume were significantly higher in participants with diabetes than those in the controls, with P = 0.001, 0.011, and 0.009, respectively. Similarly, the average kidney length, width, and volume were also higher in the diabetics than in the controls; however, only the differences in average kidney length and volume were statistically significant; P = 0.002 and 0.048, respectively [Table 2].
Correlation studies of renal volume with anthropological/biochemical parameters and age
In the diabetic group, gender had positive correlation with the left renal volume, right renal volume and average renal volume; r = 0.382, r = 0.592, and r = 0.517, respectively [Table 3]. The right renal volume increased with an increase in weight of the study subjects (r = 0.368, P = 0.046). The right renal volume and average renal volume also increased with increase in height (r = 0.524, P = 0.003 and r = 0.400, P = 0.029, respectively). Though renal volumes decreased with increasing age, this finding was not statistically significant. In the nondiabetic group, renal volume decreased with age, and they were statistically significant. Renal volumes increased with increasing weight, height, and BMI in the nondiabetic group [Table 3].
|Table 3: Correlation of renal volumes with anthropometric and biochemical variables|
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[Table 3] also shows correlations between blood pressure measurements and renal volumes in diabetics and controls. In diabetics, the average kidney volume (AKV) correlated positively with the diastolic blood pressure and mean arterial blood pressure. The left renal volume also showed positive correlation with mean arterial pressure r = 0.364, P = 0.048. In the nondiabetic group, no statistically significant correlation was established between the renal volumes and blood pressure measurements. Type of diabetes shows significant correlation with renal volumes, whereas the duration of diabetes, FBS, HbA1c and creatinine did not show significant correlation with renal volume [Table 3].
[Table 4] shows that beyond the middle age group, 51–60 years, there was a decline in renal volume with increasing age. Furthermore, significant differences between renal dimension of the participants with diabetes and nondiabetes were noted; for right kidney volume (F = 19.392, P = 0.000), for left kidney volume (F = 39.383, P < 0.000), and for AKV (F = 32.595, P = 0.000).
|Table 4: Step-wise analysis of variance of renal volumes with age between the diabetic and nondiabetic subjects|
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| Discussion|| |
The average renal volume was larger in the participants with diabetes than that in the participants without diabetes, and renal volume shows correlation with some anthropometric parameters. Unfortunately, lack of awareness among the general population that this disease condition runs a chronic course, not being aware of its complication/sequelae and that DM has symptoms that can easily be ignored, may be a major contributor to late presentation and poor compliance to therapy.
The BMI was higher in the diabetic group which corresponds to previous researches that had shown an association of type 2 DM with increased BMI., However, in the index study, the difference in BMI between diabetics and controls was not statistically significant. This is probably due to the fact that in this study a significant number of participants under type 2 diabetics were already on a weight control program, because it is known that weight loss is a recommendation for the treatment of type 2 DM.
Diabetics had a higher than normal serum creatinine values (of ≤1.2 mg/dL), though not statistically significant. The higher serum creatinine values found in diabetics likely is an indication that early renal changes may have started, even though the patients did not have clinically proven renal impairment. Consequently, renal volume loss is a late feature of renal pathology in comparison to creatinine level, which also correlates with estimated glomerular filtration rate, eGFR. We also found a positive correlation between serum creatinine levels with renal volume which was not statistically significant. This could be due to other causes of elevated serum creatinine levels in these patients such as drugs and diet.
Another biochemical parameter that was assessed in both groups was urinary albumin concentration, which was within normal limits. In the patients with diabetes with increased renal volume the normal urinary micro-albuminuria found in them could be due to the fact that renal damage might not have set in to the point of causing significantly high urinary albumin concentrations. This finding is comparable to a study reported by Mancini et al. that renal hypertrophy was present in patients without proteinuria. Another comparative study conducted by Gragnoli et al. demonstrated elevated glomerular filtration rate and increased renal volume accompanied by normo-albuminuria or micro-albuminuria.
Comparing the renal parameters of the right and left kidneys of both study groups, except for the renal width among the diabetic group which was the same for both kidneys, the left renal parameters were significantly higher than the right renal parameters. These findings are somewhat comparable to a study conducted in Pakistan, where the length of the left kidney did not significantly differ from the length of the right kidney, but was significantly bigger in width, thickness and volume compared to the right kidney. This finding further buttresses the fact that has already been known that the left kidney is bigger than the right in most people.
It was observed in this study that the renal volumes (right, left, and average) were higher in the diabetics compared to the nondiabetics, but only the right renal volume and average renal volume were statistically significant. Similar findings were reported in other studies., The increase in renal volumes in diabetics in this study is probably due to the pathophysiology of diabetic nephropathy (the arteriolar vasoconstriction increases glomerular pressure causing glomerular hypertension leading to hyper-filtration induced nephromegaly).
In this study, only the right renal volume showed positive correlation with weight and height in the diabetic group (r = 0.368, P = 0.046 and r = 0.524, P = 0.003). In contrast, in the nondiabetic group, the right and left renal volumes as well as the average renal volume showed statistically significant positive correlation with weight and height. This was similarly reported by Ohikhokhai et al. who found a strong positive relationship between renal size and some anthropometric parameters (such as weight and height).
Type 1 diabetics were fewer in the study population, but they had significantly higher renal volume compared to type 2 diabetics. This is probably due to the fact that soon after the onset of type 1 diabetes renal hypertrophy and hyper-filtration becomes manifest, which portrays a poor renal prognosis for these patients. The finding in our study was comparable to a study conducted by DallaVestra et al., who reported in their study that the effect of diabetes on the kidneys were milder in type 2 than in type 1 diabetics with the latter having higher renal volumes than the former.
Though not statistically significant, there was negative correlation between age and renal volumes in the diabetic group. In the nondiabetic group, statistically significant negative correlation was found between age and renal volumes. This could probably be due to the fact that aging processes generally causes reduction in the size of the organs and the extent of the negative correlation is less marked in the diabetic group because of the effect of diabetes on the kidneys (nephromegaly). This findings corroborate with a study conducted in Denmark among 665 adult volunteers, in which renal sizes decreased with age and was almost entirely due to parenchymal reduction. Another study found that after middle age kidney length diminished by approximately 0.5 cm per decade. The duration of diabetes was also correlated with renal volume and showed positive correlation, albeit, not statistically significant. The import of this is elucidated by a study which reported that diabetics who were diagnosed for at least 6 months had significant increase in renal volume compared with the more recently diagnosed group.
Another parameter that correlated positively (although not statistically significant) with renal volume was HbA1c. The mean value of HbA1c in this study was 9.5 ± 3.0% which reflects that there was poor glycaemic control among the study group. However a study conducted in Denmark documented statistically significant positive correlations between HbA1c and renal volume.
| Conclusion|| |
This study has shown that renal volume is increased in participants with diabetes compared with participants with diabetes. Assessment of renal volume should be part of routine evaluation of all patients with diabetes at first diagnosis as well as follow-up evaluation of these patients. This may help in the early detection of any renal disorder in these patients.
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Conflicts of interest
There are no conflicts of interest.
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