RENAL DATA FROM THE ASIA - AFRICA
Year : 2007 | Volume
: 18 | Issue : 2 | Page : 277--281
Ultrasound Assessment of Renal Size in Healthy Term Neonates: A Report from Benin City, Nigeria
AA Adeyekun1, MO Ibadin2, AI Omoigberale2,
1 Department of Radiology, University of Benin Teaching Hospital Benin -City, Nigeria
2 Department of Child Health, University of Benin Teaching Hospital Benin -City, Nigeria
A A Adeyekun
Department of Radiology, University of Benin Teaching Hospital, PMB 1111 Benin -City
Knowledge of the normal range of renal size is useful in appreciating variations that may occur due to morbidities. Ultrasound is a simple and safe method of evaluating renal sizes in all age groups. This is a prospective study of the assessment of renal dimensions in apparently healthy neonates at the University of Benin Teaching Hospital, Nigeria. One hundred and fifty neonates were studied, including eighty-five males (56.7%), and sixty-five females (43.3%). The mean length of the right kidney was 44.9 ± 3.2 mm and the mean length of the left kidney was 44.4 ± 3.5 mm. The difference in renal length between the two sides was not statistically significant. The height and weight of the child showed strong correlation with longitudinal renal measurements. The study also showed the independence of neonatal renal sizes on gender and race.
|How to cite this article:|
Adeyekun A A, Ibadin M O, Omoigberale A I. Ultrasound Assessment of Renal Size in Healthy Term Neonates: A Report from Benin City, Nigeria.Saudi J Kidney Dis Transpl 2007;18:277-281
|How to cite this URL:|
Adeyekun A A, Ibadin M O, Omoigberale A I. Ultrasound Assessment of Renal Size in Healthy Term Neonates: A Report from Benin City, Nigeria. Saudi J Kidney Dis Transpl [serial online] 2007 [cited 2022 May 17 ];18:277-281
Available from: https://www.sjkdt.org/text.asp?2007/18/2/277/32326
Ultrasound is an important imaging modality for the renal tract in children. It is well tolerated and does not involve the use of ionizing radiation or intravenous contrast medium.  In the newborns and infants, ultrasound is useful for follow-up in prenatally detected fetal hydronephrosis, , and suspected renal tract malformations suggested by clinical findings of vertebral or colonic abnormalities. In older infants and children, renal sonography may be part of the work-up for urinary tract infection, enuresis, diuresis or flank masses.  Other indications include possible obstructive uropathy, ambiguous genitalia, renal failure, and localization for closed renal biopsy.
During renal ultrasonography, one of the parameters assessed is renal size. Renal size can change in a number of morbidities and, therefore, its assessment can aid evaluation. However, this requires establishment of normal dimensions of the kidneys in various age brackets in order to appreciate deviations or alterations from normal. There are reports of some studies on renal sizes in neonates, infants and children among Caucasians, ,,, and Asians. However, reports of similar studies are rare among Africans, especially Nigerians.
The rationale for this study, therefore, is to determine the normal range of renal size in apparently healthy term Nigerian neonates, by means of ultrasonography. This would facilitate comparison with values contained in other reports and decipher, if any, racial differences in term neonates.
Patients and Methods
This study was conducted among full-term neonates (37 or more completed gestational weeks) delivered at the University of Benin Teaching Hospital (UBTH), between January and December 2004. The babies were clinically examined and then enrolled. Those with a history of birth asphyxia, or whose mothers had oligohydramnios (from birth records or ultrasound reports) - events known to influence renal size - were excluded. Another exclusion criterion was palpable abdominal mass (es), since the majority of the abdominal masses in childhood are of renal origin. Parental consent was obtained in each case. The birth weight and length (height) of each baby selected was recorded and the body mass index calculated according to the Du Bois formula.  A total of 150 (One hundred and fifty) neonates were included in the study.
A real time ultrasound scanner with a 6.5 MHz curvilinear probe (SONACE: Medison Co: South Korea) was used. The babies were scanned while held in their mothers' arms or lap or across the shoulder. Scanning was done in both supine and prone positions. Each kidney was examined in its longitudinal axis from which the bipolar length (L), and width (W) were measured in millimeters (mm). At the same point, with the transducer now transversely oriented, a third measurement (also in millimeters) was taken to obtain the antero-posterior diameter (AP) or thickness. The ultrasound machine automatically calculated the area (mm 2 ) and volume (cm 3 ), using the formula for an ellipse. 
Data handling and statistics was done using SPSS software, (version 11.0). Continuous variables were expressed as a mean ± standard deviation (SD). Student's t-test (paired and unpaired observation) was used where appropriate. The total renal length (TRL), Width (TRW), Thickness (TRT), Area (TRA) and Volume (TRV) were also calculated for both kidneys, in both supine and prone positions.
The measured values were then correlated with birth weight, body length (height) and body mass index. A p value of <0.05 was considered significant.
A total of 150 neonates were studied, which comprised 85 males (56.7%) and 65 females (43.3%).
The right kidney (mean right kidney length) was found to be slightly longer than the left (44.9 ± 3.2 mm vs. 44.4 ± 3.5 mm). The difference was, however, not statistically significant.
The total renal length (TRL), total renal area (TRA), and total renal volume (TRV) showed significant correlation with weight and height, regardless of the scanning position.
[Table 1][Table 2] as well as [Figure 1],[Figure 2],[Figure 3],[Figure 4] summarize the data on the mean renal size values for both kidneys and show scatter grams for the measured parameters for each kidney in relation to weight and height.
Ultrasound is preferred to urography for assessment of renal size since it is free of the radiographic magnification and contrastinduced increase in renal size associated with the latter. , In newborns and growing children, there is the added need to minimize exposure to ionizing radiation and intravenous contact agents. Studies on renal size in neonates abound in the foreign literature, ,,,, but this cannot be said for the Nigerian environment. This study found the right kidney to be longer than the left, in contrast with the finding of the left being longer than the right, according the study conducted by Oviasu and Benka - Coker on ultrasonic assessment of renal size in healthy Nigerian adults. 
In this study, we found the mean renal length to be 44.5 ± 3.7 mm and 44.8 ± 3.2 mm for male and female neonates respectively. This difference was not statistically significant. Lotus and others made a similar observation of the independence of renal length of gender in their study conducted on Chinese children. Komus and colleagues, in their study on Turkish children, also noted a similar trend.  It is pertinent to note that the mean value for renal length obtained in our study is similar to those obtained by Mesrobian and co-workers  in their study on Western children, perhaps confirming the independence of renal dimensions in term newborns on race. Lotus and colleagues also noted similar observations. 
This study found a significant correlation of linear renal measurements (TRL, TRW, TRA, TRV) with birth weights and heights of the subjects studied. These agree with the findings of Komus and others in Turkey  from their ultrasound assessment of normal liver, spleen and kidney dimensions in neonates, infants, and children. Measurements taken in the prone position were shown to be significantly higher than those taken in the supine position, suggesting the influence of subject's position on the measurement of renal size. De Sanctis and colleagues made a similar observation in their study on the effect of patient position on sonographic measurement of renal sizes in neonates. 
This study has established a norm for renal sizes in healthy Nigerian neonates. It found a significant correlation of renal size with birth weight and height/body length. These two body parameters should be considered as the best correlates with longitudinal renal measurements.
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