Renal Length in Chinese Children:Sonographic Measurement and Comparisonwith Western Data

William K. Loftus, FRACR,1 Roger J. Gent, DMU,2 Garry W. LeQuesne, FRACR, DDU,2

Constantine Metreweli, FRCR, FRCP1

1 Department of Diagnostic Radiology and Organ Imaging, Chinese University of Hong Kong, Shatin, NewTerritories, Hong Kong2 Department of Diagnostic Ultrasound, Women’s and Children’s Hospital, 72 King William Road,North Adelaide, South Australia 5006, Australia

Received 1 April 1997; accepted 10 October 1997

ABSTRACT: Purpose. The purpose of this study was todetermine the normal range of renal length in HongKong Chinese children and compare it with Westerndata.

Methods. Two hundred fifty children undergoingroutine abdominal sonography were examined pro-spectively, and the maximum length of 1 kidney perchild was recorded. Ages ranged from newborn to 19years, and there were 109 girls and 141 boys. Similardata from Australian children involved maximumlengths of both kidneys in 554 children ranging in agefrom newborn to 14 years. There were 361 girls and193 boys. No children had known renal disease.

Results. There was no statistically significant differ-ence between the mean renal lengths of girls andboys. Statistical comparison of the data from HongKong and Australia showed no significant differenceexcept in the 8–12 month age group (this difference isunlikely to be clinically significant). Although directstatistical comparison with published data on kidneylengths in 203 U.S. children was not possible, plots ofthe three sets of data were strikingly congruent.

Conclusions. Despite expectations that smallerbody size in Hong Kong children might equate tosmaller kidneys, comparison with 2 sets of Westerndata showed no clinically significant difference in re-nal length between the 3 groups. © 1998 John Wiley &Sons, Inc. J Clin Ultrasound 26:349–352, 1998.

Keywords: ultrasonography; renal length

Because of their smaller body size, Chinesechildren might be expected to have smaller

kidneys than Western children. If this were true,then use of the accepted Western range of normalkidney size would be inappropriate in this popu-lation and would result in overdiagnosis of‘‘small’’ kidneys. We wished to document the nor-mal range of renal length in Hong Kong Chinesechildren and compare it with data from Westernstudies.

PATIENTS AND METHODS

As part of a previous study of renal and spleniclength in Hong Kong Chinese,1 a single maximallongitudinal measurement of each kidney was ob-tained sonographically in 239 children andadults. As in the majority of previous studies,2

there was no statistically significant difference inlength between the left and right kidneys (p >0.05; paired t-test). Therefore, for the presentstudy, a single sonographic measurement ofmaximum renal length was obtained prospec-tively during routine abdominal examinations in250 Hong Kong Chinese children (newborn to 19years of age) with no known renal disease. Therewere 109 girls and 141 boys. The children wereinpatients or outpatients at a large public hospi-tal and were considered to cover all socioeconomicgroups.

Renal lengths in Hong Kong Chinese childrenwere compared with renal lengths in Australianand American children. The Australian data,which have not been previously published, date

Correspondence to: W. K. Loftus, c/o Benson Radiology, 229Melbourne Street, North Adelaide, South Australia 5006, Aus-tralia

© 1998 John Wiley & Sons, Inc. CCC 0091-2751/98/070349-04

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from 1988 and consist of single sonographic mea-surements of the maximum length of each kidneyin 554 children (newborn to 14 years of age) notknown to have renal disease. A total of 1,108 kid-neys were measured in 361 girls and 193 boys.The original data from the U.S. study of 203 chil-dren were not available, but mean lengths for dif-ferent age groups were included in the report byRosenbaum et al.3 To enable some comparison be-tween all 3 groups, the Hong Kong and Austra-lian data were divided into the same age groupsas those used in the U.S. study and plotted on thesame graph. The age groups were ‘‘x to y,’’ whereage is greater than x and less than or equal to y.A direct statistical comparison between the HongKong and Australian data was performed which,for simplicity, using the groupings already made.A p value below 0.05 (paired t-test) was consid-ered significant.

RESULTS

There was no statistically significant difference inrenal length between boys and girls (p 4 0.47). Asexpected, there was a progressive increase inmean renal length with age (Table 1).

Almost no differences in renal length betweenHong Kong and Australian children were seenover the age range for which the 2 groups over-lapped, ie, up to the age of 14 years. A statisticallysignificant difference (p < 0.05) was shown in only

1 age group, 8–12 months. Although lack of theoriginal U.S. data prevented statistical compari-son with the Hong Kong and Australian data, theplots of renal length versus age for all 3 groupsshow striking congruity (Figure 1).

DISCUSSION

The normal range of renal length at a given agemust be known before an abnormality in size canbe accurately diagnosed. This is particularly im-portant in childhood, when renal length is chang-ing with age and when renal tract abnormalities,such as reflux nephropathy, are common. Therehave been a number of studies documenting vari-ous sonographic measurements of the kidneys inchildhood. A major review4 summarizes thosestudies, endorsing the studies that measure renallength rather than those that estimate renal vol-ume. Of the former, 2 studies in particular wererecommended.3,5 In the first, 203 children in theUnited States were studied, and the report in-cluded a table of mean renal lengths at variousages and a graph that plotted mean length ± 2standard deviations against age and that could beused in the clinical setting.3 In the second study,only 122 children were examined, there was notable of mean renal lengths, and the graph plot-ting mean length, with 5th and 95th percentiles,against age was small and not easy to use.5 Otherstudies have included nomograms correlating re-nal length with weight and height but not age;however, they have not included tables relatingmean renal length to these variables.6,7 The clini-cal utility of the latter studies is reduced becausealthough renal length correlates well with bothage and height, age is a simpler variable to docu-ment.2

In the present study, we found an expected pro-gressive increase in mean renal length with age.Our earlier study had shown that there was nostatistically significant difference between thelengths of the left and right kidneys,1 and thisstudy showed none between males and females.These findings are in agreement with those inother studies.2

Despite expectations that smaller body size inHong Kong Chinese children might equate tosmaller kidneys than in Western subjects, ourstudy shows that this is not the case. There wasno practical difference in renal length betweenthe Hong Kong and Australian children studied.Although a statistically significant difference wasfound in the 8–12 month age group, it is unlikelyto be clinically significant. The relatively smallnumber of subjects in this age group in both setsof data is the most likely reason for the apparent

TABLE 1

Mean Renal Length versus Age in Hong Kong Chinese and

Australian Children

AgeGroup

Hong Kong Australia

No. ofKidneys

Mean RenalLength (cm)

No. ofKidneys

Mean RenalLength (cm)

0–4 months 21 5.0 54 5.14–8 months 22 5.7 48 5.58–12 months 11 6.3 34 5.7*1–2 years 16 6.3 114 6.22–3 years 10 6.7 124 6.83–4 years 14 7.2 114 7.24–5 years 9 7.4 134 7.45–6 years 13 8.0 110 7.86–7 years 8 7.7 68 8.07–8 years 16 8.0 60 8.38–9 years 11 8.4 62 8.69–10 years 17 8.8 48 8.7

10–11 years 10 9.1 48 9.011–12 years 10 9.4 44 9.512–13 years 7 9.2 38 9.513–14 years 19 9.6 8 10.114–15 years 9 10.1 — —15–16 years 8 9.4 — —16–17 years 10 9.9 — —17–18 years 5 10.6 — —18–19 years 4 9.6 — —Total 250 1,108

*Statistically significantly different from Hong Kong data (p < 0.05).

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FIGURE 1. Mean renal lengths by age in children from Hong Kong, Australia, and the United States.

FIGURE 2. Mean renal lengths ± 2 standard deviations by age in 554 children (1,108 kidneys) at the Women’s and Children’s Hospital, Adelaide,Australia.

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difference. Furthermore, data from the UnitedStates appear to agree closely with those fromboth Hong Kong and Australia. Thus, any of thepublished graphs should be applicable for refer-ence in any country.

From personal communications, we believethat the graph of sonographically measured nor-mal renal lengths from the Women’s and Chil-dren’s Hospital, Adelaide (Figure 2), has beenwidely used as a standard reference around theworld, although these data have never been for-mally published. We feel that the Adelaide graphmay be the best available for clinical use. Its da-tabase of 554 cases is considerably greater thanthat of other studies, and the smoothed plot ofmean length ± 2 standard deviations is ideal forreference in everyday scanning situations.

ACKNOWLEDGMENTS

We thank Wendy Tang for data collection andWillie Sung and Allan Staples for statisticalanalysis.

REFERENCES

1. Loftus WK, Metreweli C: Normal splenic size in aChinese population. J Ultrasound Med 1997;16:345.

2. Zerin M, Blane CE: Sonographic assessment of renallength in children: a reappraisal. Pediatr Radiol1994;24:101.

3. Rosenbaum DM, Korngold E, Teele RL: Sonographicassessment of renal length in normal children. AJRAm J Roentgenol 1984;142:467.

4. Edell SL, Kurtz BK, Rifkin MD: Normal renal ultra-sound measurements. In Goldberg BB, Kurtz AB,eds: Atlas of Ultrasound Measurements. Chicago,Year Book Medical Publishers, 1990, p. 146.

5. Han BK, Babcock DS: Sonographic measurementsand appearance of normal kidneys in children. AJRAm J Roentgenol 1985;145:611.

6. Dinkel E, Ertel M, Dittrich M, et al: Kidney size inchildhood: sonographical growth charts for kidneylength and volume. Pediatr Radiol 1985;15:38.

7. Blane CE, Bookstein FL, DiPietro MA, et al: Sono-graphic standards for normal infant kidney length.AJR Am J Roentgenol 1985;145:1289.

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