Nomogram of Kidney Size in Lebanon

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1 February, ; Vol2; Issue2 Nomogram of Kidney Size in Lebanon Mariam Mansour 1, Abir Fawaz 1, Soukayna Ibrahim 1, Rida Salman 2, Fouad Ziade 3, Imad Chokr 1, Khadije ElSabeh 1, Bassem Abou Merhi 1 1 Department of Pediatrics, Lebanese University-Faculty of Medical Sciences 2 Department of Radiology, American University of Beirut-Medical Center 3 Department of Statistics, Lebanese University-Faculty of Public Health Corresponding Author: Bassem Abou Merhi bassemaboumerhi@gmail.com ABSTRACT Renal size varies with age, gender, body mass index, pregnancy and co-morbid conditions. Among different growth parameters, kidney s size is considered a critical criterion used not only in clinical evaluation of renal growth, rather used in abnormalities, and diseases. Conventionally, kidney size is measured roentgenologically. Nowadays, noninvasive ultrasonography has come into general use as a screening test for the kidneys. Since the renal size is affected by several factors, it is necessary to first establish the normal values. In our study, we aim to establish nomograms for renal size in the Lebanese young population from the age of 4 to 15 years old. Methods: In a prospective study carried out on a total of 358 Lebanese schools aged renal units in 179 children aged 4 to 15 years old, were examined. Results: Kidney dimensions were analyzed in terms of renal length, width, volume, and central echogenic region for both kidneys. During the maturation process from infancy through adolescence, growth of kidney shows a high correlation with gains in height, weight and BSA. Among the body parameters, our study showed that age was the one best correlated with the kidney dimensions followed by BMI, BSA, weight and height (P<0.0001). Conclusion: It is important for Lebanese children to have their own population specific nomograms of the kidneys in the studied age group. Keywords: Body Mass Index (BMI), Body Surface Area (BSA), Weight (Wt), Height (Ht), Renal Length (L), Renal Width (W), and parenchymal thickness (PT). 1. INTRODUCTION Kidneys are in the retroperitoneal space faintly above the level of the umbilicus(1). They have an outer layer called the cortex which contains the glomerular, proximal and distal convoluted tubules and collecting ducts. Also, there is an inner layer called the medulla which contains the straight portions of the tubules, the loops of Henle, the vasa recta, and the terminal collecting ducts(1). The kidney normally contains approximately one million nephrons (glomeruli and associated tubules)(1). In humans, the formation of nephrons is complete at birth. However, functional maturation does not occur until later at advanced age(1). The main renal artery that arises off the side of the abdominal aorta supplies the kidney with blood(1). Moreover, the glomerular network of specialized capillaries plays a role as a filtering mechanism of the kidneys(1). The plasma flowing through the glomerular capillaries is filtered via the glomerular capillary walls(1). Consequently, the ultra-filtrate which is cell free contains all the substances in the

2 plasma (electrolytes, glucose, phosphate, urea, creatinine, peptides, and low molecular weight proteins), except for proteins like albumin and the globulins(1). And, the filtrate is collected after in Bowman space and goes into the tubules where its composition is modified in accordance with body needs until it leaves the kidney as urine (1). Thus, the absence of plasma proteins larger in size of albumin from the glomerular filtrate confirms the effectiveness of the glomerular capillary working as a filtration barrier(1). The kidneys work to regulate blood pressure via the renin-angiotensin-aldosterone system that controls the absorption of water and maintaining of intravascular volume. In addition, they have hormonal functions via erythropoietin, calcitriol and vitamin D activation. They could reach 6 cm of length and 24 g of weight in a full-term newborn(1). Also, kidney in human body continues to grow in size after birth and comes to near adult size of 10 cm by 12 years of age(2). A review of the literature reveals that renal size varies with age, gender, and body mass index (BMI), pregnancy and co-morbid conditions(3). Furthermore, along the maturation process from infancy through adolescence, the growth of visceral organs shows a high correlation with gains in height, weight and body surface area (BSA)(4). Considering body s parameters, height was the best correlated with kidney s dimensions followed by BSA, weight, age, BMI and gender(4). In that matter, among different growth parameters and measures, kidney s size is considered a critical criterion used not only in clinical evaluation of renal growth, rather used in abnormalities, and diseases(5). In addition, some renal diseases may change the morphological characteristics of the kidney, the size and the ultrasonography features of the tissues(6). Additionally, renal size may be an indicator of loss of kidney mass and therefore alteration of renal function(3). Thus, a child presenting for the first time with a sudden deterioration of renal functions could be diagnosed differently based on the size changes. In this case, a normal or large size might indicate an acute kidney injury(2), whereas a small size could shift the diagnosis to an acute exacerbation of chronic kidney disease(2). However, other pathologies can increase kidney s size such as polycystic disease, lipid storage disorders(2), early stage renal thrombosis, early stage diabetes mellitus and renal inflammation(3). Nonetheless, some pathology can decrease such as renal arterial occlusion and late stage renal venous thrombosis(3). Conventionally, kidney size is measured roentgenologically(7). Nowadays, non-invasive ultrasonography which is a fairly simple method has come into general use as a screening test for the kidneys(7). Other modalities such as abdominal computed tomography (CT), magnetic resonance imaging (MRI), renography and renal scintigraphy are also very common(7). Nevertheless, they have several inconvenient such as exposure to radiation, large-scale equipment, the need for the child to be calm and in a fairly immobile position during the examination, and the length of the procedure(7). The assessment of renal size is an integral part of evaluation of renal diseases for both diagnostic and prognostic purposes(8). Since the renal size is affected by several factors, it is necessary to first establish the normal values(3). Correspondingly, there are few studies to define the normal limits of organ dimensions in healthy children(9). And, it is noted that all studies were based on patient population living in Europe and the United States(10). Yet, these data are even rare among children of Eastern world and Indian subcontinent where children are constitutionally small which might affect the organs size(9). In our study, we aim to establish nomograms for renal size in the Lebanese young population from the age of 4 to 15 years old. 2. REVIEW OF LITERATURE Definition of Kidney Size The renal size can be determined by measuring renal length, renal volume and cortical volume or thickness(11). Also, renal volume assessments is an important parameter in evaluation and follow up of kidney transplant recipients, chronic renal failure and hypertension secondary to renal artery stenosis. Furthermore, it is useful in younger patients with vesicoureteral reflux which morphometrically alters the kidney(12). Although renal volume is the most accurate measurement of kidney s size since it is correlated with the subject s height, weight and total body area(2), renal volume s determination is less frequently used because it requires calculation of several measurements(13). Subsequently, it is not a precise method due to high inter-observer variation(2). Renal length is a single, directly measured assessment. Indeed, it is the most commonly used quantitative measure of renal size for purposes of comparison with established standards(13). Finally, more recent literature suggests that renal cortical thickness measured on ultrasonography is a better indicator of renal function in chronic kidney disease than length and is more closely related to estimated glomerular filtration rate(2).

3 Radiologic Modalities Previously the kidney size was accurately measured on intra venous urography, yet it had some insolvency(14). In 1962, Hodson et al. reported the renal size of 393 children based on excretory urography and created a graph of renal length in relation to the age. Other researchers reported findings that confirmed the data in the graph of Hodson et al. These results opened up a debate on the usefulness and the limitations of growth charts(15). Nevertheless, the excretory urography has some variability and a margin of an inaccuracy in the apparent size of the kidney due to various factors such as the positioning of the tube and its distance from the patient, phase of respiration, and osmotic effects of the iodinated contrast material(15). Nowadays, the advanced and sophisticated modalities of examination such as ultrasound sonography, computed tomography and magnetic resonance imaging have been effectively used for estimating the kidney size and assessing functions(12). The potential of renal sonography in children was outlined by Lyons et al. in 1972(15). Additionally, Sonographic measurement (B-mode) of renal length in 30 children was reported by Tay et al. in Anyhow, the data was compared only to excretory urography data, and the renal length was not correlated to the patient s ages(15). The ultrasound is a preferred assessment technique of the kidney size because it is free of radiographic magnification and contrast induced increase in kidney size associated with later(16). The examination is real time, tridimensional, independent of organ function and phase of respiration(8). Prenatally, ultrasound is the only useful radiographic modality to follow up fetal hydronephrosis and suspected renal tract malformation(16). In newborn, the role of kidney ultrasound is crucial to determine congenital kidneys malformations on bed side. In infant and children, kidney s sonography is a part of the work-up for urinary tract infection, enuresis, diuresis or flank masses(16). Also, other indications include suspicion of obstructive uropathy, ambiguous genitalia, renal failure, and localization for renal biopsy(16). Although ultrasound is the best radiographical modality to measure kidney dimensions, it has some limitations such as the dependence of the operator s experience, and the use of geometric assumptions about the shape of kidney to estimate kidney volumes(16). In opposition, CT scan and MRI modalities can obtain three dimensional data and therefore do not rely on geometric assumptions to estimate organs volumes(16). In the case of CT scan, some of the drawbacks are the need for ionizing radiation and potentially nephrotoxic contrast media. Similarly, the MRI also has its own limitations in clinical practice(16). With sonography, renal dimensions may be measured in different planes: sagittal, coronal and prone(11). And, the positioning on imaging plane used to measure the kidneys don t significantly affect the measurements obtained in a clinical situation(11). Additionally, sonography is one of the most common non-invasive imaging modalities used in clinical practice to measure the renal size(14). 3. OBJECTIVES The aims of this study are: to establish a nomogram for renal size in the Lebanese young and healthy population aged from 4 to 15 years old. On the other hand, it aims to evaluate the relation of renal size with different parameters such as, age, height, weight, BMI and BSA, and to identify the best parameter correlated with renal size. We also intend to compare our target nomogram with the current nomograms of renal size of other population. 4. ETHIC STATEMENT All participants involved in this study were chosen and recruited by the school at south Lebanon, and in Beirut during a scouting activity in accordance with the latest version of the declaration of Helsinki for Ethical Principles for Medical Research Involving Human Subjects. In addition, every participant has given his written informed consent which was attached with the annex. Patient Recruitment This prospective study was carried out at a school located in south Lebanon and in Beirut during a scouting activity. The participants were students and scouts referred for kidney ultrasound during voluntary kidney examination. During the period of March 2017 till July 2017, children aged between 4 to 15 years old were enrolled in this prospective study. Individuals with symptoms related to kidney pathologies, history of renal diseases including stone disease, prior abdominal surgery secondary to renal issues or disorders, pregnant women and individuals with known diabetes or hypertension were excluded from the study. Data Collection Medical records of all participants aged from 4 to 15 years old without underlying kidney disorder in the

4 period of March 2017 through July 2017 were subjected to thorough review and analysis. Our collected database consisted of information about the age, gender, blood pressure, weight, height, BSA, BMI, at the time of the ultrasound examination, and the length width and parenchymal thickness of both kidneys for each subject. 5. MATERIALS The measure tools used during our study are: pediatric manometer, weight scale, length scale and portable ultrasonography. All children were examined by PGY4 pediatric resident at the Lebanese University; specifically they were checked for short stature. All ultrasound examinations were performed by a single sonographer PGY4 radiology resident, at American University of Beirut using a sector transducer of 5 or 7.5 MHz, and a single measurement was obtained for each kidney. 6. METHODS Renal dimensions including length, width, and parenchymal thickness were sonographically measured in 194 individuals with no renal disease. Out of the 194 patients, 179 met the inclusion criteria and were included in the study, one patient was excluded for malignant disease with abdominal surgery, one patient was excluded for having short stature and finally 13 patients aged between 1 month and 4 years and above 15 years were excluded since they constituted very small group. An analysis was performed for differences due to age, gender and laterality. Patients were required to empty their bladders before the examination to prevent hydrationassociated increase in renal length. Measurement techniques and parameters were defined before initiating the study. The renal length (L) referred to the longest pole to pole distance, measured in one position (supine) and averaged. Also, the renal width (W) was defined as the maximum dimension in the transverse cross-section at the level of the renal hilum. Furthermore, the central echogenic region was included in measurements. Finally, the parenchymal thickness (PT) was identified as the combined thickness of the cortex and medulla measured at the upper and lower poles and averaged. The patient s blood pressure, height (Ht), and weight (Wt) were measured immediately before the ultrasound examination. Height was measured without footwear, using a stadiometer. Whereas, Body mass index (BMI) and body surface area (BSA) were calculated using the following formulae: BMI = Wt /Ht2 (Wt in Kilograms and Ht in meter) BSA = (2&(Ht Wt) 3600) (Wt is in Kilograms and Ht in centimeter) The correlation of renal dimensions with anthropometric parameters like weight, height, body mass index (BMI) and body surface area (BSA) was analyzed. Statistical Analysis Data was presented as mean standard deviation (SD) of the children characteristics, right renal measures and left renal measures for age groups (years) from 4 to 15 years old. The statistical difference among the groups was determined by ANOVA test. Correlation coefficient was obtained by Person coefficient regression equation and scatter plots for the renal length and volume (Right and Left) vs. age (years). Statistical analysis was performed using SPSS package version RESULTS A total of 358 renal units in 179 patients were analyzed. There were 74 male and 105 female patients. The age ranged from 4 to 15 years. The distribution of age in the study population was as follows: 11 patients (4 yrs.), 21 (5 yrs.), 13 (6 yrs.), 27 (7 yrs.), 13 (8 yrs.), 20 (9 yrs.), 12 (10 yrs.), 12 (11 yrs.), 20 (12yrs.), 11 (13 yrs.), 10 (14 yrs.), and 9 (15 yrs.). Mean and Standard Deviation of children s characteristics for weight, height, body mass index and body surface area by age in years were calculated (Table1). Mean and Standard Deviation of renal length, width, volume, and central echogenic region for right kidney by age in years were studied (Table 2). Mean and Standard Deviation of renal length, width, volume, and central echogenic region for left kidney by age in years were also studied (Table 3).

5 Table 1: Mean and Standard Deviation (SD) of Children Characteristics by Age in Years. Table 2: Mean and Standard Deviation (SD) Renal Length, Width, Volume, and Central Echogenic Region for Right Kidney by Age in Years Table 3: Mean and Standard Deviation (SD) Renal Length, Width, Volume, and Central Echogenic Region for Left Kidney by Age in Years

6 The relationship of mean right renal length without SD, plotted against various age in years (Figure 1). Numbers plotted followed this following formula: Renal Length (Right) = 0.27 Age (Years) Figure 1: Right Renal Length in Centimeter vs. Age in Years The relationship of mean left renal lengths without SD, plotted against various age in years (Figure 2). Numbers plotted followed the following formula: Renal Length (Left) = 0.24 Age (Years) Figure 2: Left Renal Length in Centimeter vs. Age in Years Right and left renal lengths and volumes were correlated to body indices namely age in years, height in cm, weight in kg, BSA and BMI, were individually assessed using Pearson's correlation coefficient, which showed a positive correlation of renal length with age (r = 0.78 for right kidney and r = 0.72 for left kidney), body weight (r = 0.79 for right kidney and r = 0.75 for left kidney), BMI (r = 0.43 for right kidney and r = 0.76 for left kidney), and BSA (r = 0.83 for right kidney and r = 0.69 for left kidney) and a positive correlation of renal volume with age (r = 0.66 for right kidney and r = 0.63 for left kidney), body weight (r = 0.65 for right kidney and r = 0.60 for left kidney), BMI (r = 0.68 for right kidney and r = 0.64 for left kidney), and BSA (r = 0.60 for right kidney and r = 0.55 for left kidney).these relations are depicted in Table 4. Multiple regressions performed on these data gave the following equations for determining renal length and volume from anthropometric parameters and P-Value for all characteristics was significantly positive <

7 Table 4: Correlation of Children Characteristics with Renal Length and Volume for Right and Left Kidneys The renal volumes compared between left and right kidneys and were comparable but when compared both to other population such as Nomasa study (Takayo Nomasa, Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume Medical Journal, 48, , 2001, Japan) and results were evidently different with smaller and lesser volume of our kidneys population group (Figure 3). Figure 3: Comparison of Renal Volume between Lebanese and Nomasa Study 8. DISCUSSION Our total population in Lebanon reached almost about four million citizens and the present study assessed a total of 358 Lebanese school aged renal units in 179 patients were analyzed. There were 74 male and 105 female patients. The age ranged from 4 to 15 years (Table 1). The normal values of kidneys dimensions are important parameters during sonographic examinations(17). To the best of our knowledge, literature reviewed showed that this study covers the unique large series of pediatric kidney dimensions by sonography involving Lebanese population. The scan and measurements in this study were performed by a certified one single sonographer. A previous study has shown that experience has an influence on measurement accuracy during ultrasound scanning(18). In the present study, kidney dimensions were analyzed in terms of renal length, width, volume,

8 and central echogenic region for both kidneys from 4 to 15 years were studied which are simple, reproducible, reliable and objective measurements. Mean and Standard Deviation of renal length, width, volume, and central echogenic region for right and left kidneys by age in years were studied (Table 2 and 3). Our study measurements of both kidneys support the historical assessment of kidney size based on longitudinal length measurement and volume. The present study has shown that there were no significant differences in the renal volume and length with respect to gender. This finding is similar to the findings of other previous authors(19, 20, 21, 22). Therefore, gender certainly is not a determining factor for kidney dimensions in school-age children in this population. This suggests that special tables based on gender are not necessary. The morphology of kidney varies from person to person. During the maturation process from infancy through adolescence, growth of kidney shows a high correlation with gains in height, weight and BSA(19, 23). Among the body parameters, our study showed that BSA was the best correlated with the kidney dimensions followed by height, Age, weight and BMI. These results were also supported by the variance and covariance of the correlation coefficients (Table 4). This observation probably results from rapid body growth that occurs before the attainment of mature body morphology at adult stage. But since it is easier to create a nomogram for renal size based on age then BSA, the normal limits of the kidneys were, therefore, defined according to age in the present study. Konus et al.(19) also reported that kidney dimensions showed the best correlation with body height in a Caucasian children population. Soyupak et al.(21) and Safak et al.(19), however, reported that kidney dimensions showed the best correlation with body weight among the children population they studied. These differences with the present study may be due to variations in race or different ethnic origins. The normal limits of the kidneys were defined according to age in this study. Numbers were plotted following this invented formula: Renal Length (Right) = 0.27 Age (Years) To determine the relationship of mean right renal length without SD against various age in years (Figure 1). Also numbers plotted followed the second invented formula: Renal Length (Left) = 0.24 Age (Years) To determine the relationship of mean left renal lengths without SD against various age in years (Figure 2). In this pilot study using Pearson's correlation coefficient, showed a positive correlation of renal length and volume with age, BMI, and BSA, weight and height. Multiple regressions performed on the data gave the equations for determining renal length and volume from anthropometric parameters as for age, weight, height, BMI and BSA and the p-value for all characteristics was significantly positive < (Table 4). The renal volumes compared between left and right kidneys and were comparable but when compared both to other population such as Nomasa study (Takayo Nomasa, Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume Medical Journal, 48, , 2001, Japan) and results were evidently different with smaller and lesser volume of our kidneys population group (Figure 3). The implication from our study for the Lebanese ultrasound community is obvious because of possible variations in the anthropometric parameters of various populations, races and regions. It is important for Lebanese children to have their own population specific nomograms of the kidneys in the studied age group as American and European population data cannot be used as universal patterns. Our results could be extrapolated to the wider international community where there is need for each country to establish their own specific nomograms of kidney size in school-age children with reference to the body parameter that shows the best correlation with kidney dimensions as height might show variation in different ethnic origins or races. 9. LIMITATIONS The limitations of this study include the fact that it was done in Beirut and south Lebanon only where a multicenter study in other regions might improve the precision of the estimates and also the generalizability of the data. The socio-economic status of children estimated was not recorded, although some of them belonged to lower middle and lower income groups. Even though the number studied was very good and has high power of the study but the age could be started from birth till 18 years of age. 10. CONCLUSION The established normal parameters can be used to determine the pathologic changes in the size of the kidneys in routine sonographic examination of school age children 4 to 15 years of age in Lebanese

9 population. The prediction model of the normal kidney dimensions can serve as an alternative method for sonographers assessing kidney size and volume in a busy practice setting or in remote locations in the Lebanese population. Any specific longitudinal dimension of the kidney should primarily be correlated with patient age, BMI, and BSA, weight and height and findings should be compared with tables of normal parameters. REFERENCES 1. Jerry M. Bergstein. Introduction to glomerular diseases. In: Richard E. Behrman, Robert M. Kliegman, Hal B. Jenson. Nelson textbook of pediatrics. 16th edition. Philadelphia, London, Toronto, Montreal, Sydney, Tokyo: W.B. Saunders Company; P Madhuri Kanitkar, Kidney Size- What is Normal? Indian Pediatrics. July 2012; volume: Niels-Peter, Buchholz, Farhat Abbas, Syed Raziuddin Biyabani, Qaiser Javed, Jamsheer Talati, Masood Afzal, Imtiaz Rizvi. Ultrasonographic renal size in individuals without known renal disease. Journal of Pakistan Medical Association. January Cu Eze, KK Agwu, DN Ezeasor, KK Agwuna, AE Aronu, EI Mba. Sonographic biometry of normal kidney dimensions among schoolage Children in Nsukka, Southeast Nigeria. West Indian Med J Jan; 63(1): Jun-Hwee Kim, MD, Myung-Joon Kim, MD, Mi-Jung Lee, MD, Length and volume of morphologically normal kidneys in Korean ultrasound measurement and estimation using body size, Korean. J Radiol July Aug; 14(4): T.Gavela, M.SanchezBayle, G.GomezMardones, S.Gallego, J Martinez Perez, M.T.Pintado, ultrasonographic study of kidney size in children. NEFROLOGIA. 2006; volume 26. numero Takayo Nomasa. The standart renal volume of Japanese boys and girls determinmed by three dimensional Ultrasonography. Kurume Medical Journal. 2001; 48, AOtiv, K Mehta, UAli, MNakarni. Sonographic Measurement of Renal Size in Normal Indian Children. Indian Pediatrics. July 2012; volume Thapa NB, Shah S, Pradhan A, Rijal K, Pradhan A, Basnet S. Sonographic Assessment of the Normal Dimensions of Liver, Spleen, and Kidney in Healthy Children at Tertiary Care Hospital. Kathmandu university medical journal. J 2015; 52(4): Ph Petit, R Auquier, M Panuel,S Aillaud,V Doucet, F Faure, B Bourliere Njean, Ph Devred. Is ultrasound evaluation of kidney length children possible? Journal dr radiologie. Avril 1999; vol 80, N Mujahid Raza, Amina Hameed, M Imran Khan. Ultrasonographic assessment of renal size and its correlation with body mass index in adults without Known renal disease. J Ayub Med Coll Abbottabad. 2011; 23 (3). 12. H. Krishna Moorthy, P.Venugopal. Measurement of renal dimensions in vivo: A critical appraisal. Indian Journal of Urology. 2011; 27(2): Julia Tucker De Sanctis, Susan A. Connolly, Robert T. Bramson. Effect of patient position on sonographically measured renal length in neonates, infants and children. AJR. May 1998; Dr. Ravikumar Nalli, Dr. Anita S, Dr. C. Venkateshwara reddy. To determine the renal size in normal children by ultrasonography. IOSR Journal of Dental and Medical Sciences. Apr.2016; volume 15. Issue David M. Rosenbaum, Eric Korngold, Rita Littelwood Teele. Sonographic assessment of renal length in normal children. AJR. March 1984; 142: Sabina Sultana, Shafiqur Rahman, Biplob Kumar Basak, Nilofar Shameem Afza, Md Nurul Hossain, Sarwar Ferdaus. Determination of Kidney Length and Volume by Ultrasound in 100 Term Bangladeshi Newborn. Bangladesh. J Child Health. 2012; vol 36 (1): Mittal R, Chowdhary DS. A pilot study of the normal measurements of the liver and spleen by ultrasonography in the Rajasthani population. J Clin Diagn Res. 2010; 4: Eze CU, Ezugwu FO, Agbo JA. Sonographic determination of fetal gender in the second and third trimesters in a private hospital in Enugu, southeast Nigeria. Radiography. 2010; 16: Konus OL, Ozdemir A, Akkaya A, Erba G, Celik H, Isik S. Normal liver, spleen and kidney dimension in neonates, infants and children: evaluation with sonography. Am J Roentgenol. 1998; 171: Safak AA, Simsek E, Bahcebasi T. Sonographic assessment of the normal limits and percentile curves of liver, spleen and kidney dimensions in healthy school-aged children. J Ultrasound Med. 2005; 24: Soyupak SK, Narli N, Yapicioglu H, Satar M, Sungur EH. Sonographic measurements of the liver, spleen and kidney dimensions in the healthy term and preterm newborns. Eur J Radiol. 2002; 43: Ortiz-Neira CL, Traubici J, Alan D, Moineddin R, Shuman C, Weksberg R, et al. Sonographic assessment of renal growth in patients with Beck-with-Wiedemann syndrome: the Beckwith-Wiedemann syndrome renal nomogram. Clinics (Sao Paulo) 2009; 64: Megremis SD, Vlachonikolis IG, Tsilimigaki AM. Spleen length in childhood with US: normal values based on age, sex, and somatometric parameters. Radiology. 2004; 231: