abdominal radiographs and ultrasonograms from miniature schnauzer dogs and other dog 
 breeds , which presented to the department of radiology at the seoul national university 
 veterinary medical teaching hospital from february 2012 to april 2014 and from february 2014 
 to april 2014 , respectively , were retrospectively evaluated . dogs with no evidence of 
 clinical and subclinical renal disease by physical examination , clinical sign , serum 
 chemistry ( blood urea nitrogen , creatinine , calcium , phosphorus , glucose , total protein and 
 albumin ) and electrolytes , no ultrasonographic abnormalities of kidneys ( normal cortical and 
 medullary echogenicity , smooth contour , no focal lesion or pyelectasia ) and with normal 
 lumbar vertebral column were included . a normal lumbar vertebral column was defined as one 
 with 7 segments , no transitional vertebra and no evidence of disease that could affect 
 vertebral length . in addition , at least one kidney had to be measureable on either 
 ventrodorsal or right lateral view . dogs with systemic hypertension , immune - mediated 
 disease , diabetic mellitus , urine specific gravity < 1.015 , proteinuria ( confirmed by the 
 urine protein : creatinine ratio or significant protein detection on a dip stick ) or age under 
 1 year old were excluded from the study . taking the effect of body weight on kidney size 
 into account , radiographs were obtained using a direct digital radiography system with a focal film 
 distance of 100 cm . ultrasound scans 
 were performed using 49 or 410 mhz microconvex and 512 or 513 mhz linear probes 
 ( sa-9900 , medison , seoul , korea ; and aloka prosound 7 , hitachi aloka medical ltd . , tokyo , 
 japan ) . ventrodorsal and right lateral radiographs and ultrasonograms were retrieved and 
 reviewed in all dogs . radiographic measurements : the radiographs were evaluated in random order 
 with a dicom workstation ( infinitt pacs , infinitt healthcare co. , ltd . , on ventrodorsal radiographs , kidney length and the length and width of 
 l2 were measured . on right lateral radiographs , kidney length and the length and height of 
 l2 kidney length was measured as the maximum distance between the cranial and 
 caudal poles of the kidney [ 13 , 19 , 20 ] . l2 length was measured at 
 the level of midpoint parallel to the long axis of the vertebral body on ventrodorsal 
 radiographs and at the level of the origin of the transverse processes parallel to the long 
 axis of the vertebral body on right lateral radiographs . the width and height of l2 were measured at the level where the caudal 
 borders of the transverse processes meet the vertebral body on ventrodorsal and right 
 lateral radiographs , respectively . all 
 measurements were made three times by one observer ( j.s . ) , and mean values were 
 obtained . radiographic kidney size : in each dog , both the left and right kidney 
 sizes were calculated by dividing the kidney length by the l2 length on both ventrodorsal 
 and right lateral radiographs [ 6 , 9 , 11 , 13 , 19 , 20 , 27 ] . radiographic l2 length : in each dog , the radiographic l2 length was 
 calculated as the ratios of l2 length to width ( l2l / l2w ) on ventrodorsal radiographs and l2 
 length to height ( l2l / l2h ) on right lateral radiographs . ultrasonographic kidney size : in each dog , the ultrasonographic kidney 
 size was calculated by dividing the kidney length by the aortic luminal diameter using 
 recorded values from preserved images in which both the left and right kidney lengths on the 
 dorsal plane and aortic luminal diameter on the longitudinal plane had been measured by 
 original examiners . group : measurements and calculated ratios were compared between miniature 
 schnauzer dogs and other dog breeds . the group of other dog breeds was further divided into 
 either the brachycephalic or nonbrachycephalic group and either the chondrodystrophoid or 
 nonchondrodystrophoid group . intra- and interobserver repeatability and reproducibility of radiographic 
 measurements : abdominal radiographs from 20 randomly selected dogs were evaluated 
 by three observers ( j.s . kidney length and the length , width and height of 
 l2 were measured three times by each observer independently . each of three measurements was 
 compared to evaluate the intraobserver repeatability in each observer , and the mean values 
 of three measurements in each observer were compared to evaluate interobserver 
 reproducibility . statistical analysis : descriptive statistics were calculated for all 
 measurements of the left and right kidneys and l2 . left and right kidney sizes on either the ventrodorsal or right lateral radiograph and mean 
 kidney sizes on the ventrodorsal and right lateral radiographs in each group were compared 
 using an independent samples t - test . left and right kidney sizes on 
 ultrasonograms were compared using a paired samples t - test . radiographic 
 kidney size , radiographic l2 length and ultrasonographic kidney size in the miniature 
 schnauzer group and the group of other dog breeds , as well as the effect of sex on 
 radiographic kidney size , were compared using an independent samples 
 t - test . radiographic kidney size and l2 length in brachycephalic , 
 nonbrachycephalic , chondrodystrophoid and nonchondrodystrophoid groups were compared with 
 those in the miniature schnauzer group and each other using one - way anova . correlations of 
 radiographic kidney size with age , body weight and radiographic l2 length were assessed 
 using the pearson s correlation coefficient . correlations of body weight with l2 length , 
 width and height and radiographic l2 length were also assessed using the pearson s 
 correlation coefficient . intra- and interobserver repeatability and reproducibility were 
 evaluated using the intraclass correlation coefficient ( icc ) . all statistical tests were performed by 
 one of the authors ( j.s . ) using spss ( ibm spss statistics for windows , version 21.0 , ibm 
 corp . , forty - nine miniature schnauzer dogs and 54 other dog breeds without clinical evidence of 
 renal disease and lumbar vertebral abnormality were included . other dog breeds consisted of 
 maltese ( n=12 ) , shih tzu ( n=8 ) , poodle ( n=5 ) , dachshund ( n=4 ) , bichon fris ( n=3 ) , cocker 
 spaniel ( n=3 ) , pekingese ( n=3 ) , pug ( n=3 ) , yorkshire terrier ( n=3 ) , chihuahua ( n=2 ) , 
 miniature pinscher ( n=2 ) , pomeranian ( n=2 ) , beagle ( n=1 ) , bulldog ( n=1 ) , papillon ( n=1 ) and 
 spitz ( n=1 ) . shih tzu , pekingese , pug , chihuahua and bulldog were included in the brachycephalic group 
 ( n=17 ) , and the others were included in the nonbrachycephalic group ( n=37 ) . the 
 chondrodystrophoid group ( n=31 ) included shih tzu , poodle , dachshund , bichon fris , cocker 
 spaniel , pekingese , pug , beagle and bulldog , and the others were included in the 
 nonchondrodystrophoid group ( n=23 ) . mean ages and body weights were 10.08  3.05 ( range 117 ) years and 8.21  1.78 ( range 
 4.914.7 ) kg in the miniature schnauzer group , and 8.80  3.32 ( range 117 ) years and 5.90  
 3.26 ( range 1.915 ) kg in other dog breeds . there were 5 intact males , 23 castrated males , 7 
 intact females and 14 spayed females in the miniature schnauzer group and 4 intact males , 26 
 castrated males , 15 intact females and 9 spayed females in other dog breeds . radiographic measurements : in the miniature schnauzer group , 46 left 
 kidneys ( 93.9% ) and 41 right kidneys ( 83.7% ) were measureable on ventrodorsal radiographs , 
 and 45 left kidneys ( 91.8% ) and 28 right kidneys ( 57.1% ) were measureable on right lateral 
 radiographs . in other dog breeds , 52 left kidneys ( 96.3% ) and 36 right kidneys ( 66.7% ) were 
 measureable on ventrodorsal radiographs , and 46 left kidneys ( 85.2% ) and 35 right kidneys 
 ( 64.8% ) were measureable on right lateral radiographs . l2 length , width and height were 
 measurable on both ventrodorsal and right lateral radiographs from all of dogs . radiographic kidney size : radiographic kidney sizes calculated from the 
 measurements in the miniature schnauzer group and other dog breeds are summarized in table 1table 1.radiographic kidney size in the miniature schnauzer and other dog breedsmedianmean  sdrangeminiature schnauzerk / l2vd ( n=48)3.343.36  0.262.833.95k / l2rlat ( n=48)3.283.27  0.272.653.93k / l2mean ( n=49)3.293.31  0.262.743.94other dog breedsk / l2vd ( n=53)2.962.97  0.282.513.63k / l2rlat ( n=49)2.932.91  0.272.483.60k / l2mean ( n=54)2.942.94  0.272.493.62sd : standard deviation , k : kidney length , l2 : second lumbar vertebra length , vd : 
 ventrodorsal radiograph , rlat : right lateral radiograph , mean : mean ratio of 
 k / l2vd and k / l2rlat , a ) significant difference vs. other dog 
 breeds ( p<0.001 ) .. in each group , the ratios of left kidney length to l2 length were not 
 significantly different from those of right kidney length to l2 length on both ventrodorsal 
 and right lateral radiographs . in addition , the mean ratios of left and right kidneys on 
 ventrodorsal views ( k / l2vd ) were not significantly different from those on right 
 lateral views ( k / l2rlat ) . consequently , further statistical evaluation was 
 performed using the mean ratios of k / l2vd and k / l2rlat 
 ( k / l2mean ) . sd : standard deviation , k : kidney length , l2 : second lumbar vertebra length , vd : 
 ventrodorsal radiograph , rlat : right lateral radiograph , mean : mean ratio of 
 k / l2vd and k / l2rlat , a ) significant difference vs. other dog 
 breeds ( p<0.001 ) . the k / l2mean ratios in the miniature schnauzer group ( 3.31  0.26 ) were 
 significantly higher than those in other dog breeds ( 2.94  0.27 ) 
 ( p<0.001 ) . interestingly , the k / l2mean ratios in 12 of 49 
 ( 24.5% ) miniature schnauzer dogs were above 3.5 , whereas those in only 2 of 54 ( 3.7% ) dogs 
 in other dog breeds were above 3.5 ( one of maltese dogs and a chihuahua ) . among other dog breeds , the k / l2mean ratios were 2.86  0.28 in the 
 brachycephalic group , 2.98  0.27 in the nonbrachycephalic group , 2.94  0.24 in the 
 chondrodystrophoid group and 2.95  0.33 in the nonchondrodystrophoid group . the 
 k / l2mean ratios in the miniature schnauzer group were significantly higher than 
 the other 4 groups ( p<0.001 ) . 1.boxplot of the mean kidney length to second lumbar vertebra length ratio ( k / l2mean ) 
 in different breed groups . sch , miniature schnauzer ; bc , brachycephalic breed ; nbc , 
 nonbrachycephalic breed ; cd , chondrodystrophoid breed ; and ncd , 
 nonchondrodystrophoid breed . ) . boxplot of the mean kidney length to second lumbar vertebra length ratio ( k / l2mean ) 
 in different breed groups . sch , miniature schnauzer ; bc , brachycephalic breed ; nbc , 
 nonbrachycephalic breed ; cd , chondrodystrophoid breed ; and ncd , 
 nonchondrodystrophoid breed . the k / l2mean ratios in the miniature schnauzer group significantly differed 
 between male and female dogs regardless of whether the dogs were neutered or not 
 ( p=0.015 ) , whereas no such difference was found in other dog breeds 
 ( p=0.094 ) . however , mean differences were relatively small in both 
 groups : 0.18 in the miniature schnauzer group and 0.13 in other dog breeds . there was no 
 significant difference between intact ( intact male and female ) and neutered ( neutered male 
 and female ) dogs both in the miniature schnauzer group ( p=0.216 ) and other 
 dog breeds ( p=0.394 ) . there were no significant relationships between the 
 k / l2mean ratios and ages and between the k / l2mean ratios and body 
 weights both in the miniature schnauzer group ( r=0.150 , p=0.304 ; and 
 r=0.136 , p=0.362 , respectively ) and other dog breeds ( r=0.052 , 
 p=0.709 ; and r=0.068 , p=0.630 , respectively ) ( figs . 2.scatterplot of the mean kidney length to second lumbar vertebra length ratio 
 ( k / l2mean ) in miniature schnauzer dogs in relation to age ( a ) and body weight ( bw ) 
 ( b ) . and 3fig . 3.scatterplot of the mean kidney length to second lumbar vertebra length ratio 
 ( k / l2mean ) in other dog breeds in relation to age ( a ) and body weight ( bw ) ( b ) . ) . scatterplot of the mean kidney length to second lumbar vertebra length ratio 
 ( k / l2mean ) in miniature schnauzer dogs in relation to age ( a ) and body weight ( bw ) 
 ( b ) . scatterplot of the mean kidney length to second lumbar vertebra length ratio 
 ( k / l2mean ) in other dog breeds in relation to age ( a ) and body weight ( bw ) ( b ) . radiographic l2 length : l2 length , width and height were significantly 
 correlated with body weight in the miniature schnauzer group ( r=0.643 , 
 p<0.001 ; r=0.556 , p<0.001 ; and r=0.503 , 
 p<0.001 , respectively ) and other dog breeds ( r=0.873 , 
 p<0.001 ; r=0.817 , p<0.001 ; and r=0.815 , 
 p<0.001 , respectively ) . taking the effect of body weight on l2 length 
 into account , l2 length was divided by either l2 width ( l2l / l2w ) or height ( l2l / l2h ) , and 
 both l2l / l2w and l2l / l2h values were constant regardless of body weight in the miniature 
 schnauzer group ( r=0.055 , p=0.712 ; and r=0.019 , p=0.897 , 
 respectively ) and other dog breeds ( r=0.080 , p=0.574 ; and r=0.224 , 
 p=0.111 , respectively ) . l2l / l2w and l2l / l2h ratios were 1.11  0.06 and 
 2.50  0.18 in the miniature schnauzer group , and 1.21  0.09 and 2.66  0.32 in other dog 
 breeds . although both values were significantly correlated with radiographic kidney size 
 ( r=0.563 , p<0.001 ; and r=0.250 , p=0.011 ) , correlations 
 were relatively low . as l2l / l2w values were better correlated with radiographic kidney size , 
 l2l / l2w values were selected for further statistical analysis . the ratios of l2l / l2w were significantly lower in the miniature schnauzer group than other 
 dog breeds ( p<0.001 ) . among other dog breeds , the l2l / l2w ratios were 
 1.20  0.10 in the brachycephalic group , 1.21  0.08 in the nonbrachycephalic group , 1.20  
 0.10 in the chondrodystrophoid group and 1.22  0.06 in the nonchondrodystrophoid group . only the miniature schnauzer 
 group had significantly lower values compared to each group ( p<0.001 , 
 respectively ) ( fig . 4.boxplot of the second lumbar vertebra length to width ratio ( l2l / l2w ) in different 
 breed groups . sch , miniature schnauzer ; bc , brachycephalic breed ; nbc , 
 nonbrachycephalic breed ; cd , chondrodystrophoid breed ; and ncd , nonchondrodystrophoid 
 breed . ) . boxplot of the second lumbar vertebra length to width ratio ( l2l / l2w ) in different 
 breed groups . sch , miniature schnauzer ; bc , brachycephalic breed ; nbc , 
 nonbrachycephalic breed ; cd , chondrodystrophoid breed ; and ncd , nonchondrodystrophoid 
 breed . ultrasonographic kidney size : the left and right kidney lengths were 
 significantly different in both the miniature schnauzer group ( p<0.001 ) 
 and other dog breeds ( p=0.004 ) , and right kidneys were larger in both 
 groups . however , mean differences were just 1.88 mm in the miniature schnauzer group and 
 1.13 mm in other dog breeds ; therefore , the left and right kidney lengths were considered 
 similar in practical terms . k / ao 
 ratios were 6.75  0.67 in the miniature schnauzer group and 7.16  1.01 in other dog 
 breeds . even though there was a significant difference between those groups 
 ( p=0.015 ) , k / ao ratios in all the dogs in both groups were within or very 
 close to normal range : those in 2 miniature schnauzer dogs ( 5.48 and 5.49 ) and 2 other dog 
 breeds ( 5.48 and 9.15 ) were out of , but very close to , normal range . intra- and interobserver repeatability and reproducibility of radiographic 
 measurements : for all the measurements from 20 randomly selected dogs , intra- and 
 interobserver repeatability and reproducibility showed excellent correlation ( iccs of all 
 measurements > 0.9 ) . in this study , the radiographic kidney size in miniature schnauzer dogs was significantly 
 larger than that of other dog breeds . the standard normal radiographic kidney size in adult 
 dogs may not be valid for miniature schnauzer dogs , as radiographic kidney sizes in 24.5% of 
 miniature schnauzer dogs were greater than 3.5 . on the other hand , the radiographic kidney 
 size in other dog breeds was consistent with previous reports [ 6 , 9 , 13 , 19 , 20 ] . a recent study compared the radiographic kidney sizes in dogs with different skull types 
 ( brachycephalic , mesaticephalic and dolichocephalic ) and different body weights ( 010 kg , 
 > 1030 kg and > 30 kg ) . the study showed 
 significant differences between skull types and body weights , especially between 
 brachycephalic and dolichocephalic dogs and between small breed ( 10 kg ) and large breed 
 dogs ( > 30 kg ) . however , the effect of breed on kidney size irrespective of body weight or 
 the effect of body weight on kidney size irrespective of breed was not fully explained in 
 spite of the fact that breed and weight are interrelated . in this study , only small- to 
 medium - sized dogs ( 15 kg ) were included to prevent differences resulting from body weight , 
 and no differences between breeds except for miniature schnauzers as well as between body 
 weights were identified . thus , the radiographic kidney size was considered to be influenced 
 by body weight rather than breed . one previous study reported a negative correlation between 
 body weight and kidney volume per kilogram body weight . there was a small but significant difference between dogs with different sexes in the 
 miniature schnauzer group regardless of their neutering state , as males had larger kidneys . previous studies also reported 
 inconsistent results : one study reported that kidney size was slightly larger in male dogs , 
 another feline study reported that intact cats had larger kidneys , and another canine 
 studies reported that there were no differences between sexes [ 4 , 19 , 20 , 22 , 28 ] . the results of this study and previous studies may indicate that sex 
 has a minor effect on kidney size . there was no correlation between age and kidney size , 
 which was consistent with previous reports [ 9 , 19 , 20 ] . whereas l2 vertebral length , width and height were related to body weight , l2l however , like kidney size , l2 lengths 
 were variable between individuals , so that the correlation between radiographic l2 length 
 and radiographic kidney size was significant but relatively low . in spite of that , l2l / l2w 
 ratios were significantly lower in miniature schnauzer dogs than in other dog breeds . in 
 addition , there were no significant differences between other dog breeds , and even 
 chondrodystrophoid breeds have a similar l2 length to other dog breeds , which indicates that 
 miniature schnauzer dogs have breed - specific short vertebra . furthermore , ultrasonographic kidney sizes ( k / ao ratios ) , which were not affected by l2 
 length , in all the dogs in the miniature schnauzer and other dog breeds were within or very 
 close to normal range , supporting the notion that the large radiographic kidney size in 
 miniature schnauzer dogs was attributed to their short l2 length , not their long kidney 
 length . thus , care should be taken when using vertebral length to assess organ size in 
 miniature schnauzer dogs , such as heart size and colon diameter on radiographs and kidney 
 size on ultrasonograms , as well as radiographic kidney size [ 2 , 16 , 26 ] . the radiographic evaluation of organ size has inherent 
 disadvantages of variable degrees of magnification and distortion . one study reported that a 
 considerable degree of magnification may result depending on the distances between an object 
 and film : a 10-cm distance led to 19% magnification . however , a number of previous studies reported relatively consistent 
 radiographic kidney size in various breeds of dogs , which may indicate that variable degrees 
 of magnification of kidney and l2 lengths may not lead to significant deviations from the 
 standard normal ranges of radiographic kidney size [ 6 , 
 9 , 11 , 13 , 19 , 20 ] . in addition , one human study reported that renal 
 inclination did not lead to significant error in the radiographic measurement of kidney 
 length in most cases . second , actual kidney size 
 was not measured by necropsy , and more accurate methods to measure kidney size using ct and 
 mri were not used . in this study , ultrasonographic kidney size using the k / ao ratio was used 
 as a reference . however , the k / ao ratio was not a gold standard used to evaluate kidney 
 size . moreover , to assume actual kidney size , whether the k / ao ratio on ultrasonograms is 
 superior to the k / l2 ratio on radiographs has not been studied . however , previous studies 
 reported that radiographic and ultrasonographic kidney lengths were closely correlated with 
 actual kidney size , and in this study , using the k / ao ratio was sufficient to prove that 
 absolute kidney length was not the factor leading to significant differences in radiographic 
 kidney size by comparing kidney length with different anatomic structures , l2 and the aorta . third , this study included dogs without clinical evidence of renal disease , and thus , dogs 
 with subclinical renal disease may be included in this study . finally , changes in 
 radiographic kidney size in miniature schnauzer dogs with renal disease and comparison with 
 each breed were not studied , and further study research is needed . in conclusion , miniature schnauzer dogs have breed - specific short vertebrae and 
 consequently a larger radiographic kidney size . in this study , the normal radiographic 
 kidney size of miniature schnauzer dogs was 3.31  0.26 , which was greater than the standard 
 reference in normal adult dogs . thus , care should be taken when evaluating radiographic 
 kidney size in miniature schnauzer dogs to prevent falsely diagnosed renomegaly .
kidney size may be altered in renal diseases , and the detection of kidney size alteration 
 has diagnostic and prognostic values . we hypothesized that radiographic kidney size , the 
 kidney length to the second lumbar vertebra ( l2 ) length ratio , in normal miniature 
 schnauzer dogs may be overestimated due to their shorter vertebral length . 
 this study was 
 conducted to evaluate radiographic and ultrasonographic kidney size and l2 length in 
 clinically normal miniature schnauzers and other dog breeds to evaluate the effect of 
 vertebral length on radiographic kidney size and to reestablish radiographic kidney size 
 in normal miniature schnauzers . 
 abdominal radiographs and ultrasonograms from 49 miniature 
 schnauzers and 54 other breeds without clinical evidence of renal disease and lumbar 
 vertebral abnormality were retrospectively evaluated . 
 radiographic kidney size , in the 
 miniature schnauzer ( 3.31  0.26 ) was significantly larger than that in other breeds ( 2.94 
  0.27 ) . 
 relative l2 length , the l2 length to width ratio , in the miniature schnauzer 
 ( 1.11  0.06 ) was significantly shorter than that in other breeds ( 1.21  0.09 ) . however , 
 ultrasonographic kidney sizes , kidney length to aorta diameter ratios , were within or very 
 close to normal range both in the miniature schnauzer ( 6.75  0.67 ) and other breeds ( 7.16 
  1.01 ) . 
 thus , miniature schnauzer dogs have breed - specific short vertebrae and 
 consequently a larger radiographic kidney size , which was greater than standard reference 
 in normal adult dogs . 
 care should be taken when evaluating radiographic kidney size in 
 miniature schnauzers to prevent falsely diagnosed renomegaly .