Sonographic Measurement of Splenic Length:Correlation with Measurement at Autopsy

William K. Loftus, FRACR,1 Louis T. C. Chow, FRCPath, FRCPA,2

Constantine Metreweli, FRCR, FRCP1

1 Department of Diagnostic Radiology and Organ Imaging, Prince of Wales Hospital, Chinese University of HongKong, Shatin, New Territories, Hong Kong2 Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, Chinese University of Hong Kong,Shatin, New Territories, Hong Kong

Received 1 May 1997; accepted 19 August 1998

ABSTRACT: Purpose. The purpose of this study was todetermine the correlations between the sonographicmeasurement of splenic length and the actual spleniclength, volume, and weight.

Methods. Before autopsy, sonographic measure-ments of splenic length were obtained in 30 cadavers,and these values were compared with the actuallength, volume, and weight of the spleen at autopsy.

Results. There were clear linear correlations be-tween maximum sonographic length and actuallength (r = 0.831), volume (r = 0.817), and weight (r =0.810).

Conclusion. This study shows that a single, simplesonographic measurement gives a clinically useful in-dication of true splenic size. © 1999 John Wiley &Sons, Inc. J Clin Ultrasound 27:71–74, 1999.

Keywords: ultrasonography; spleen; autopsy; mea-surement

Splenomegaly is important because it may bethe only indication of a serious underlying

disease process such as lymphoma. The diagnosisof gross splenomegaly should be straightforward;however, mild splenomegaly may not be palpableclinically, and sonography may be the first meansby which it is detected. There are a number ofsources of potential error in sonographic mea-surement. These include physical limitations inresolution, technical limitations, errors in scan-ning technique, and errors in interpretation.1 Al-lowing for these, however, it is assumed that a

linear correlation exists between the sonographicmeasurements and the actual dimensions of theparts being measured.

Two articles have shown a linear correlationbetween the sonographic measurement of thesplenic area and the actual splenic volume orweight following removal of the organ at surgeryor autopsy. Koga2 used a previously describedcomplex sonographic method3 to calculate thesplenic area in 10 patients before the spleen wasremoved at surgery (8 patients) or autopsy (2 pa-tients) and the splenic volume was determined bya water displacement method. Ishibashi et al4 re-ported findings of splenic weight at autopsy com-pared with the calculation of splenic area made bysonography performed within the previous 30days in 22 patients. Both studies showed a verygood correlation between splenic area as deter-mined by sonography and actual splenic volume(r 4 0.956) and weight (r 4 0.924), respectively.Ishibashi et al4 also found that the ‘‘spleen index’’(transverse diameter × vertical diameter on theimage on which the cross-sectional area of thespleen was greatest) correlates well with splenicweight (r 4 0.901).

The methods for calculating the splenic areaand the spleen index are quite unwieldy and notsuitable for routine clinical practice. Given thecomplexity of calculating these figures, it is likelythat splenic area and spleen index are only rarelyestimated and that, in the usual clinical situation,only a single measurement of splenic length isobtained. However, a direct correlation betweensonographically measured splenic length and ac-tual splenic length or volume has not been dem-

Correspondence to: W. K. Loftus, Benson Radiology, 229 Mel-bourne Street, North Adelaide, South Australia 5006, Austra-lia

© 1999 John Wiley & Sons, Inc. CCC 0091-2751/99/020071-04

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onstrated. Such a demonstration was the aim ofthis study.

MATERIALS AND METHODS

Forty-seven cadavers were examined before au-topsy. Excluded from the study were cases withmassive splenomegaly that precluded an accuratesonographic measurement of length on a singleimage, cases with evidence of splenic trauma, andcases in which it was difficult to identify thesplenic margins or, indeed, to image the spleen atall. Thirty cases were included in the study. Themean age of subjects at death was 65 years [stan-dard deviation (SD), 16.5 years; range, 30–86years]. There were 17 men and 13 women. A por-table Aloka SSD-500 ultrasound scanner (Aloka,Tokyo, Japan) with a 3.5-MHz curved-arraytransducer was used, and in each case, the great-est splenic length was measured on 3 separateimages, typically in an oblique sagittal plane andthrough the hilum (Figure 1). Both the maximumand mean lengths were recorded.

At autopsy, the spleen was removed, and themaximum splenic length was measured with aruler. The spleen was weighed, and the splenicvolume was determined by a water displacementdevice constructed at our institution. Patientheight was recorded but not body weight.

Data were analyzed to determine the degree ofcorrelation between the sonographic measure-ments and the actual lengths, weights, and vol-umes of the spleens. Linear correlation of best fitand 2-tailed significance tests were used; p valuesbelow 0.05 were considered significant. Becauseour study focused solely on the correlation of mea-surements, splenic pathology was not recorded.Our data on normal splenic size in this populationwere previously published.5

RESULTS

The mean value for the mean sonographic spleniclengths was 8.84 cm (SD, 2.00 cm; range, 5.5–13.4cm), and the mean for the maximum sonographiclengths was 9.3 cm (SD, 2.1 cm; range, 5.6–14.5cm). The means for the actual splenic dimensionswere 10.5 cm (SD, 3.0 cm; range, 3.0–15.1 cm) forlength, 110 cm3 (SD, 70 cm3; range, 26–250 cm3)for volume, and 123 g (SD, 70 g; range, 27–279 g)for weight. The majority of subjects had maxi-mum sonographic splenic lengths within the nor-mal range established for this population.5 Foursubjects had enlarged spleens, presumably re-lated to an underlying disease process. In all but4 subjects, the actual splenic length was greaterthan the maximum sonographic length. The meanvalue for the absolute difference between actualand maximum sonographic length was 1.4 cm.

There was a good correlation between themaximum sonographic length and the actualsplenic length (r 4 0.831; p < 0.001) (Figure 2),and there was a close correlation between maxi-mum sonographic length and both splenic volume(r 4 0.817; p < 0.001) (Figure 3) and splenicweight (r 4 0.810; p < 0.001). A linear correlationmodel provided the best fit with the data in eachcase. The correlation between mean sonographiclength and all variables was not as good as thatbetween the maximum sonographic length andthese variables. Correlation values of 0.797,0.779, and 0.786 were found between mean sono-graphic length and actual length, volume, andweight, respectively (p < 0.001). Because the ac-tual length was nearly always greater than thesonographic length, the mean sonographic lengthcorrelated less well than did the maximum sono-graphic length. A strong correlation was foundbetween actual length and volume (r 4 0.831; p <0.001) and between actual length and weight (r 40.828; p < 0.001). As expected, there was a goodcorrelation between splenic volume and weight (r4 0.958; p < 0.001), but the correlation betweenpatient height and all splenic measurements waspoor (r 4 0.4073, p 4 0.025 for splenic length; r

FIGURE 1. Sonogram of cadaver spleen. Arrowheads indicate calipersmeasuring splenic length.

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4 0.5303, p 4 0.003 for splenic volume; r 40.4628, p 4 0.01 for splenic weight).

DISCUSSION

Our results show a clear linear relationship be-tween the sonographic measurement of spleniclength and the actual length, volume, and weightas measured at autopsy. Because the spleen is asoft organ, it might be expected to change shapeand elongate when removed from the body. Thiscould explain why the actual length was usuallygreater than the maximum sonographic measure-ment. Other likely causes of the differences in-clude the physical and technical limitations of thescanner used and those of sonography in general.On the other hand, blood flow in a living patientmay distend the spleen and could result ingreater sonographic length in living patients thanthat measured in cadavers.

That the sonographic measurement correlatesclosely with the actual splenic volume is impor-tant because a measurement of increased lengthat sonographic examination is interpreted as in-dicating an increase in actual splenic volume.

This close correlation means that a sonographicdiagnosis of mild splenomegaly can be made withconfidence. Interestingly, and of practical impor-tance, the single maximum sonographic measure-ment was more accurate than the mean of the 3sonographic measurements, in contrast to resultsusing a similar sonographic method for assessingkidney length.6

Several practical difficulties may prevent accu-rate sonographic measurements in cadavers. Notonly does the absence of peristalsis make thebowel less easy to differentiate from solid viscera,but static, fluid-filled hollow viscera can have anechotexture very similar to that of the spleen.This is particularly true of the stomach, whichwas often difficult to clearly separate from thespleen. The reduced amount of air in the lungs isalso problematic because it diminishes the clarityof the diaphragm and therefore the superior mar-gin of the spleen. These are some of the reasonswhy sonographic measurements in cadavers arelikely to be less accurate than those made in liv-ing subjects. Therefore, the correlation betweensonographic measurement of splenic length andactual length and volume may be different in

FIGURE 2. Scatterplot of maximum sonographic (US) measurements of splenic length versus actual length atautopsy in 30 cadavers.

SONOGRAPHIC VERSUS ACTUAL SPLENIC LENGTH

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clinical practice than found in this autopsy study.Nevertheless, the use of a simple, single sono-graphic measurement is clinically useful, and wesuggest that it be performed routinely. The morecomplicated techniques involving calculation ofsplenic area and spleen index can be reserved forproblematic cases or cases in which there is a highclinical suspicion of splenomegaly.

ACKNOWLEDGMENTS

We thank Mr. Stephen Cheung for assistancewith data collection and Ms. Willie Sung for dataanalysis.

REFERENCES

1. Burns PN, Waldroup L, Pinkney MN. Limitationsof ultrasound imaging measurement. In: Goldberg

BB, Kurtz AB, editors. Atlas of ultrasound mea-surements. Chicago: Year Book Medical Publish-ers; 1990. p 1.

2. Koga T. Correlation between sectional area of thespleen by ultrasonic tomography and actual vol-ume of the removed spleen. J Clin Ultrasound1979;7:119.

3. Koga T, Morikawa Y. Ultrasonographic determina-tion of the splenic size and its clinical usefulness invarious liver diseases. Radiology 1975;15:157.

4. Ishibashi H, Higuchi N, Shimamura R, et al. Sono-graphic assessment and grading of spleen size. JClin Ultrasound 1991;19:21.

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

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

FIGURE 3. Scatterplot of maximum sonographic (US) measurements of splenic length versus actual volumeat autopsy in 30 cadavers.

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