|Year : 2015 | Volume
| Issue : 3 | Page : 123-127
Sonographic measurement of renal dimensions of adults in northwestern Nigeria: a preliminary report
Sadisu Mohammed Maaji1, Odunko Daniel2, Bappa Adamu3
1 Department of Radiology, Usumanu Dan Fodiyo University, Sokoto, Nigeria
2 Department of Radiology, Federal Medical Center, Birnin Kebbi, Nigeria
3 Department of Medicine, Nephrology Unit, Bayero University, Kano, Nigeria
|Date of Submission||02-Dec-2015|
|Date of Acceptance||21-May-2015|
|Date of Web Publication||3-Sep-2015|
Sadisu Mohammed Maaji
Department of Radiology, Usumanu Dan Fodiyo University, Sokoto
Background: The kidney size of a patient is a valuable diagnostic parameter in urological and nephrology practice. Renal size may be an indicator for the loss of kidney mass and, therefore, kidney function. Because many renal disorders are associated with changes in the sizes of the kidneys, normative standards for assessing renal size have been developed and are widely used in clinical practice. Ultrasound imaging is relatively inexpensive, fast, noninvasive, and free of radiation and has largely replaced the intravenous urogram as the first modality for the evaluation of the urinary system. The aim of this study was to establish some normal preliminary renal dimensions data of Nigerian population in Northwestern Nigeria. Materials and Methods: Renal ultrasound measurements were performed on 104 consecutive volunteers without known kidney pathology in a tertiary institution between January and December 2013. Ethical permit was obtained from the Ethical Committee of the Hospital. There were 50 females and 54 males. Before proceeding to ultrasound scanning, the procedure was explained to the respondents, and their consent obtained. The longitudinal length, width, thickness and volume of the right and left kidney were measured. In addition, the age, sex, weight, body mass index, and height of the respondents were recorded. All renal scans were done with a single real-time dynamic ultrasound scanner (concept D) using a 3.5 MHZ curvilinear probe. Hard copy images were taken for documentations, and all the measurements were done by two trained radiologists to reduce intraobserver errors. Results: A total of 104 volunteers, 50 females and 54 males were scanned. The mean age was 30.4 ± standard deviation 19 years (18-70). The mean kidney length was 11.3 ± 8.8 and 11.6 ± 9.8 for right and left kidney, respectively. The mean height and weight was 1.67 ± 0.85 and 70.9 ± 11.2, respectively. The mean kidney width was 4.4 ± 0.71 and 5.2 ± 5.26 for right and left kidney, respectively. The mean renal thickness was 4.7 ± 0.67 and 4.5 ± 0.68 for right and left kidney, respectively. The renal volume was 109.6 ± 29.3 on the right and 119.7 ± 32.8 on the left. The body mass index was calculated to be 25.1 ± 3.96 (16.18) and 26.0 ± 5.36 (24.7) for female and male, respectively. Renal measurements were correlated with the subject's height, weight, body mass index using the Pearson's correlation. The strongest correlation with renal volume is age, the correlation coefficient was 0.997 (P < 0.001). Conclusion: We established valuable normal values of renal dimensions in the adult Nigerian population (North Western region). The weight, height, body mass index were also taken into consideration with positive correlations between renal volume and age, height, and body mass index.
Keywords: Adults, dimensions, renal, ultrasound
|How to cite this article:|
Maaji SM, Daniel O, Adamu B. Sonographic measurement of renal dimensions of adults in northwestern Nigeria: a preliminary report
. Sub-Saharan Afr J Med 2015;2:123-7
|How to cite this URL:|
Maaji SM, Daniel O, Adamu B. Sonographic measurement of renal dimensions of adults in northwestern Nigeria: a preliminary report
. Sub-Saharan Afr J Med [serial online] 2015 [cited 2020 Apr 9];2:123-7. Available from: http://www.ssajm.org/text.asp?2015/2/3/123/164420
| Introduction|| |
The kidney size measurements of a patient are a valuable diagnostic parameter for urologist and nephrologists. Renal size may be an indicator of the loss of kidney mass and, therefore, kidney function. , Because many renal disorders are associated with changes in the sizes of the kidneys, normative standards for assessing renal size have been developed and are widely used in clinical circumstances. ,,,,,, End stage renal disease is a major problem in both developing and developed countries. , Since the renal size is affected by various diseases, it is important to establish the baseline normal renal values. The information available in the Europe and North America may not be applicable to our population since the renal size may differ between ethnic groups and according to body size. ,,, Ultrasound imaging is relatively inexpensive, fast, noninvasive, and free of radiation and has largely replaced the intravenous urogram as the first modality for the evaluation of the urinary system. Its portability and simplicity make it an indispensable modality over computerized imaging tomography or intravenous urography. ,,, There are some few literature on normal renal sizes estimation by ultrasonography in Nigeria, and this study is the first in this part of Northwestern Nigeria. The aim of this study was to establish normal preliminary renal measurement data in the Nigerian population living in some part of the Northwestern region.
| Materials and methods|| |
Renal ultrasound measurements were performed on 104 consecutive volunteers without known kidney pathology or any systemic diseases in a tertiary Hospital between January and December 2013. Ethical permit was obtained from the Ethical Committee of the Hospital, and informed consent was also obtained from the volunteers all the patient's blood pressure, serum creatinine, and fasting blood sugar were within normal range. There were 50 females and 54 males. Before proceeding to ultrasound scanning, the procedure was explained to the respondents, and their consent obtained. The subjects included in this study do not have any prior history of kidney disease. Clear gel was applied on the patient skin over the area to be scan. Images were obtained in supine, left and right lateral positions with the subjects holding their breath during image accusation. All renal scans were done using a single real-time dynamic ultrasound scanner (concept D) using a 3.5 MHZ curvilinear probe. Hard copy images were taken for documentations, and all the scans were done by two trained radiologists to avoid inter and intra observer variability. The maximal longitudinal axis was evaluated with the ultrasound calipers placed on the outer edges of the caudal and cranial side in the sagittal plane to obtain the maximum longitudinal renal length.  [Table 1] shows comparison of renal parameters with other studies. [Figure 1] shows a longitudinal ultrasound of the right kidney. The width was measured from the transverse ultrasonographic section of the kidney almost perpendicular to the longitudinal length. The renal thickness or depth was also measured as the distance between ventral and dorsal surfaces of the kidney. The renal volume of both kidneys was automatically generated by the machine using ellipsoid formula. In addition, the age, sex, weight, body mass index, and height of the respondents were recorded. At the end of the scanning, the gel was wiped off.
|Figure 1: Longitudinal ultrasound of the right kidney demonstrating renal length|
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| Results|| |
A total of 104 volunteers, 50 females and 54 males were scanned. The mean age was 30.4 ± standard deviation 19 years (18-70). The mean kidney length was 11.3 ± 8.8 and 11.6 ± 9.8 for right and left kidney, respectively. The mean height and weight was 1.67 ± 0.85 and 70.9 ± 11.2, respectively. The mean kidney width was 4.4 ± 0.71 and 5.2 ± 5.26 for right and left kidney, respectively. The mean renal thickness was 4.7 ± 0.67 and 4.5 ± 0.68 for right and left kidney, respectively. The renal volume was 109.6 ± 29.3 and 119.7 ± 32.8 for right and left kidney, respectively. The body mass index was calculated to be 25.1 ± 3.96 (16.18) and 26.0 ± 5.36 (24.7) for female and male, respectively. Renal measurements were correlated with the subject's height, weight, body mass index using the Pearson's correlation. The strongest correlation with renal volume is the age, the correlation coefficient was 0.997 (P < 0.001).
| Discussion|| |
Renal size was conventionally determined on urography by measuring the renal length. In addition, measurements made by computed tomography, magnetic resonance imaging or angiograms can be used interchangeably with those made by renal ultrasound. The measurements obtained by these methods were associated with various drawbacks. Renal ultrasound is the modality of choice because is readily available and does not involve the use of ionizing radiation; however, there are some limitations such as variations in observers' skill and interpretation. Ultrasound is widely used due to its noninvasiveness, reproducibility, and accessibility.  In our study, we analyzed renal sizes in terms of length, width, thickness as well as renal volume. Our data agreed with the previous studies that left kidney is larger than the right. ,, The difference in size may be because the left kidney has more space to grow than the right kidney. The presence of the liver on the right may have more impact on renal growth when compared to the spleen on the left. Furthermore, the left renal artery is shorter and straighter than the right; the increased blood flow in the left renal artery may result in relatively increased in volume. ,
The overall mean renal length in a study done in Southeast Nigeria in 2005 for left and right kidney was 10.6 cm and 10.3 cm, respectively,  these values are slightly lower than values in our study. These differences could be as a result of environmental, genetic and nutritional factors. This result showed that we cannot use the same normogram for different ethnicities from the same country. In a study done in Denmark  the mean renal length is 11.2 cm and 10.9 cm for left and right kidney, respectively, these values are slightly similar to the current study. However, the mean renal volume in our study is lower than that of the Denmark study. Renal measurements were correlated with the subject's height, weight, body mass index using the Pearson's correlation. The strongest correlation with renal volume is the age, the correlation coefficient was 0.997 (P < 0.001). Kang et al.  in their study show the average weight of 63 kg of their subjects, whereas the average weight is higher in our study with value of 70.9 kg. Studies done by Fernandes et al.  and others in Pakistan  highlight the necessity of investigating renal dimensions for each population, strengthening that European and American populations data cannot be used as universal patterns.
Age is also important as both physiology and anatomy of the human body alters with age. It is established that by 70 years, as much as 30-50% of cortical glomeruli atrophy; manifested by a progressive loss in renal mass.  Renal dimensions remain essentially unchanged between the ages of 30 and 60 years, however, a significant reduction in size was observed in older age group. Postmortem studies have shown that weight of kidney is approximately 19% lower in elderly compared with young adults. , The loss of renal volume with aging may be caused by cellular senescence, glomerulosclerosis, tubulointerstitial fibrosis, vascular collapse, and thickening. Other important factors include oxidative stress, alterations of cytokines, and growth factors. ,
Our study agreed with the findings that males have larger kidney volume, with volume of 206 cm 3 and 205 cm 3 for both right and left kidneys, respectively, however, there were no gender-related differences in renal length. , Zeb et al.  documented that body surface area was the most sensitive indicator in their study, a finding which agrees both with literature and logic since organ size is unquestionably related to body size. Zeb et al.  infer that body habitus and built is a major predictor of renal size in healthy adults; some parameters may have greater impact than others, but it is the amalgam of these anthropometric measurements which determines kidney size in healthy individual. Renal ultrasonography, therefore, is considered the gold standard to measure kidney size because magnetic resonance imaging is expensive and not readily available. Although ultrasound measured kidney volume is more to be a superior correlate of kidney mass, in a larger study involving 665 healthy volunteers has shown that the bipolar kidney length is the most practical measurement of kidney size. 
Normal renal length varies from 100 to 124 mm in different population ,, and dependent on ethnic background, side and sex. While population-based studies are needed to establish the normal values for Nigerian individuals our study show a mean length of 11.6 cm and 11.3 cm left and right, respectively. These values are slightly higher when compared with the Indo-Asian average length of 10.4 cm and is probably a reflection of the relatively small body size of most of the Indo-Asians.
Some of the limitations in our study are the smaller sample size. The sample size must be large enough to detect the clinically important effect.  However, because of cost implication study with an overlarge sample is not necessary as it seems unethical to involve unnecessary extra subjects. 
| Conclusion|| |
We established valuable normal values of renal dimensions in our adult Nigerian population in some part of Northwestern region. The weight, height, body mass index were also taken into consideration with positive correlations between renal volume and age as well as height and body mass index. The study was done with one ultrasound machine to avoid false-positive findings. We recommend a multicenter study so that we can document a gender and age specific normal renal dimensions for adequate comparison in the evaluation of renal diseases.
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Conflicts of Interest
There are no conflicts of interest.
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