AJR 2005; 184:45-49
© American Roentgen Ray Society
Sonographic Evaluation of Spleen Size in Tall Healthy Athletes
Audrey L. Spielmann1,
David M. DeLong2 and
Mark A. Kliewer3
1 Vancouver General Hospital, Department of Radiology, Vancouver Coastal Health,
899 W 12th Ave., Vancouver, BC V5Z 1M9, Canada.
2 Department of Radiology, Duke University Medical Center, Box 3808, Durham, NC
27710.
3 Department of Radiology, University of Wisconsin Hospital & Clinics, 600
Highland Ave., Madison, WI 53792-3252.
Received March 24, 2004;
accepted after revision June 1, 2004.
Address correspondence to A. L. Spielmann.
Abstract
OBJECTIVE. The purpose of this study was to establish the range of
spleen sizes in tall healthy athletes.
SUBJECTS AND METHODS. Sonographic measurements of spleen size and
left renal length were performed on 129 college athletes (82 men, 47 women).
Length, width, and thickness of the spleen and left renal length were
obtained. In addition, the height, weight, and age of each athlete were
recorded. Pearson's product moment correlation coefficients were calculated,
and linear regression analysis was used to create a model for calculating
normative values.
RESULTS. The mean body height for men was 74.3 (189 cm) ±
(SD) 3.7 inches (9 cm) and for women was 69.3 (176 cm) ± 3.7 inches (9
cm). Spleen length was greater than 12 cm in 31.7% of the men (mean spleen
length, 11.4 ± 1.7 cm) and in 12.8% of the women (mean spleen length,
10.3 ± 1.3 cm). In women, height correlated with spleen length
(r = 0.3, p = 0.05), width (r = 0.4, p =
0.01), and volume (r = 0.3, p = 0.02) but not with thickness
(r = 0.08, p = 0.6). Spleen length did correlate with left
renal length (r = 0.5, p = 0.0005). In men, height
correlated with spleen length (r = 0.4, p = 0.0003), width
(r = 0.5, p = 0.0001), and volume (r = 0.4,
p = 0.0002) and less with thickness (r = 0.3, p =
0.01). Spleen length and left renal length were poorly correlated (r
= 0.2, p = 0.04). Regression analysis showed that in women taller
than 5 ft 6 inches (168 cm), the mean splenic length of 10 cm increased by 0.1
cm for each 1-inch incremental increase in height. In men taller than 6 ft
(180 cm), the mean splenic length of 11 cm increased by 0.2 cm for each 1-inch
incremental increase in height.
CONCLUSION. Spleen size correlates with height in tall healthy
athletes. Nomograms from this data can be used to gauge the risk of returning
to play after episodes of acute splenomegaly, as with infectious
mononucleosis.
Introduction
The accurate diagnosis of splenic enlargement is a matter of considerable
importance for athletes of unusual size and height. Although splenic
enlargement can be the result of a number of disorders (including infectious,
infiltrative, immunologic, and malignant conditions), viral illnesses are by
far the most common cause in the young population of college athletes. Splenic
enlargement is particularly marked with infectious mononucleosis, a condition
endemic on college campuses and one that places the patient at risk for
splenic rupture. Although spontaneous rupture of the spleen is both uncommon
and rarely fatal, most athletic team physicians will exclude athletes with
mononucleosis from vigorous activity and contact sports until their spleen
size returns to normal and the athletes feel well.
Determining when it is safe for the young athletes to return to play is not
straightforward. In the intensely competitive arena of modern collegiate
sports, there is often pressure on physicians by coaches and the players
themselves to sanction the resumption of play at the earliest possible time.
The physical examination is unreliable to assess for splenic enlargement and
therefore has been largely supplanted by imaging studies, particularly
sonography. For the sonographic diagnosis and monitoring of splenomegaly,
standards of normal spleen sizes have been developed for the general
population, but not for those patients whose body habitus and size are at the
extremes of the normal range. The extrapolation of data from the general
population to those of unusual height is a dubious strategy. To our knowledge,
this is the first study that has evaluated spleen size in the very tall
population. The purpose of this study then was to determine normative spleen
data for taller athletes to diagnose more accurately splenomegaly in this
population and to better guide decisions regarding the safety of returning to
contact sports.
Materials and Methods
Student athletes participating in basketball, football, volleyball, and
soccer programs at a single large university were recruited for the study and
prospectively evaluated during their preseason annual physical examinations.
One hundred twenty-nine healthy students were assessed (82 men and 47 women).
Predetermined exclusion criteria for this study included a history of
splenectomy, a recent history of infectious mononucleosis (within the past 6
months), age younger than 18 years, a history of malignancy, hematologic
disorders, prolonged febrile illness, or chronic fatigue syndrome. Our
institutional review board approved the study, and informed consent was
obtained in all subjects.
All sonographic studies were performed on an HDI 5000 or 3500 sonographic
unit (ATL-Philips) with a curvilinear 2-5-MHz transducer (C5-2 probe,
ATL-Philips). The subjects were placed in a supine or right posterior oblique
position and scanned during suspended respiration. The spleen size was
measured in the sagittal plane in the standard oblique coronal orientation to
record the maximal length (in centimeters) of the spleen. The transverse
plane, perpendicular to the oblique coronal plane, was then measured to record
the transverse width and anteroposterior thickness (in centimeters) and width
or thickness (in centimeters) of the spleen (Figs.
1A and
1B). The transverse dimension
of the spleen was measured as the greatest dimension in the transverse plane,
and the width was measured as the shortest distance from the hilum to the
outer convexity of the spleen. The sonographic program calculated volume in
cubic centimeters (using the formula for a prolated ellipse). The length of
the left kidney was also documented. The same experienced sonographic
technologist performed all of the scanning with a radiologist in attendance.
In addition, the height and weight of the subjects were recorded.
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Fig. 1A. —19-year-old man standing 6 ft 2.5 inches (189 cm).
Longitudinal sonogram shows craniocaudal length of spleen to be 16.05 cm.
Electronically enhanced measurement cursors show measurement technique.
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Pearson's product moment correlation coefficients were calculated for each
of the variables, and linear regression analysis was used to create a
predictive model for normative values of spleen size dimensions in this
population.
Results
The average age of the participants was 19 ± 1 year. For the men,
the mean height was 74.3 (189 cm) ± (SD) 3.7 inches (9 cm) (range,
65-83 inches [165-211 cm]) and the mean weight was 220 (100 kg) ± 40.5
lb (18 kg) (range, 153-332 lb [69-150 kg]). The mean splenic dimensions were
11.4 ± 1.7 cm sagittal (range, 8.2-16.1 cm), 10.8 ± 1.4 cm
transverse (range, 8-14 cm), 5.0 ± 0.8 cm in width, and 333.6 ±
116.1 cm2 in volume. The mean left kidney length was 11.1 ±
0.9 cm; 31.7% of the men had a spleen length of greater than 12 cm and 13.4%
had a spleen length of greater than 13 cm. In men, height correlated with
spleen length (r = 0.4, p = 0.0003)
(Fig. 2), transverse dimension
(r = 0.5, p = 0.0001)
(Fig. 3), and volume
(r = 0.4, p = 0.0002) but less with width (r = 0.3,
p = 0.01). The left kidney length correlated with the transverse
measurement of the spleen (r = 0.4, p = 0.001) and weakly
with the splenic length (r = 0.2, p = 0.03). All splenic
measurements correlated better with height than weight. Subject height
correlated poorly with left kidney length (r = 0.2, p =
0.04). Regression analysis showed that in men taller than 72 inches (183 cm),
the mean splenic length of 11 cm increased by 0.2 cm for each inch of increase
in height. The representative 95% confidence intervals were calculated at
4-inch intervals (Table 1).
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TABLE 1 Men: Mean and Upper Limit of the Normal Range of Spleen Length for
Increments of Body Height by Linear Regression Method
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For the women, the mean body height was 69.3 (176 cm) ± 3.7 inches
(9 cm) (range, 61-78 inches [155-198 cm]) and the mean weight was 152 lb (69
kg) (range, 125-185 lb [57-84 kg]). The mean splenic dimensions were 10.3
± 1.3 cm sagittal (range, 7.9-13.9 cm), 9.5 ± 1.2 cm transverse
(range, 7-13.1 cm), 4.2 ± 0.7 cm in width, and 220.3 ± 67.4
cm2 in volume. The mean kidney length was 10.3 ± 1.1 cm;
12.8% of the women had a spleen length of greater than 12 cm. In women, body
height correlated with spleen length (r = 0.3, p = 0.05)
(Fig. 4), width (r =
0.4, p = 0.01) (Fig.
5), and volume (r = 0.3, p = 0.02), but not
thickness (r = 0.08, p = 0.6). The left kidney length
correlated with spleen length (r = 0.5, p = 0.0005),
transverse dimension (r = 0.4, p = 0.006), and volume
(r = 0.4, p = 0.002). The spleen size and renal length
correlations were stronger in women than in men. Splenic measurements did not
correlate with subject weight. In women, subject height did correlate with
left kidney length (r = 0.5, p = 0.0002). Regression
analysis showed that in women taller than 66 inches (168 cm), the mean splenic
length of 10 cm increased by 0.1 cm for each inch increase in height.
Representative 95% confidence intervals were calculated
(Table 2).
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TABLE 2 Women: Mean and Upper Limit of the Normal Range of Spleen Length for
Increments of Body Height by Linear Regression Method
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Discussion
With infectious mononucleosis, splenomegaly may be clinically palpable as
early as the second week of illness, but the clinical examination of splenic
size is notoriously inaccurate. In one study evaluating spleen size in
patients with sarcoidosis, splenomegaly was present in 57% of the patients
(using sonographic criteria to evaluate size) but only clinically palpable in
8% [1]. The range in reported
sensitivity of assessing splenomegaly by palpation of the abdomen varies from
50% at best to the more realistic estimate of 17%
[2]. Therefore, imaging has
become essential for the accurate assessment of spleen size, the serial
monitoring of spleen size over course of the patient's illness, and
development of guidelines for return to play. In these guidelines, it is
generally recommended to withhold the athlete from vigorous sports until the
spleen has returned to normal size
[3]. The problem is that
current standards of spleen size may not be applicable to the very tall
individual.
In this study, we found that standard charts for spleen size may be
misleading in the subpopulation of very tall individuals. Although the mean
spleen size in this group falls within the normal range, the upper limit of
the normal range needs to be revised upward (Tables
1 and
2). Graphic representation of
the data shows some variability of spleen size by height but also an
unmistakable trend for the spleen length to increase in taller individuals
(Figs. 2,
3,
4,
5). By way of illustration,
Figures 1A and
1B shows the sonographic images
of a large spleen (16.05-cm length, 13.35-cm transverse) in a healthy male
subject who was 6 ft 2.5 inches (189 cm) in height.
Some investigators have sought to establish an internal reference standard
against which spleen size can be calibrated. The most common such strategy is
to compare the length of the spleen to the length of the left kidney. Loftus
and Metreweli [4] proposed a
spleen-kidney ratio of 1.25, as measured on sonography, as the upper limit of
normal in a pediatric population. In our study, spleen length was correlated
with kidney length in women, but not in men. We therefore found the
spleen-kidney ratio to be an unreliable index for spleen size. Rather we
propose the use of the look-up Tables
1 and
2 as references for daily use
in a busy practice setting.
Several prior studies have sought to develop standards for spleen size,
using a variety of imaging techniques, such as CT, scintigraphy, MRI, and
sonography One study used four measurements from two imaging planes in the
volume formula for an ellipsoid to estimate splenic volume
[5]. The spleen, however, has a
variable 3D configuration, and its shape does not easily conform to the simple
geometry of an ellipsoid. Therefore, volumetric measurement is obtained most
accurately on CT or MRI [6].
Nevertheless, routine CT for the diagnosis and serial follow-up of patients
for suspected splenic enlargement is difficult to justify in view of the
radiation exposure (especially in a pediatric or young adult population) and
the expense. As an alternative, MRI is hampered by expense and limited
availability in many areas of the world. One group estimated the normal
splenic volume using 3D sonography in 52 normal volunteers
[7]. The 3D technique was
believed to provide a more accurate measurement of the spleen volume than
conventional sonographic techniques but was cumbersome and time-consuming and
therefore not practical for a busy sonographic practice. A recent study
comparing sonography with CT for the estimation of splenic volume proposed the
following formula:
 |
as the most accurate estimation of splenic volume on sonography
[8]. Regardless, many studies
indicate that volumetric data are cumbersome, inherently flawed considering
the complex 3D shape of the spleen, and usually not required to guide the
clinical management of splenomegaly. As a practical clinical guideline, the
distance that the spleen extends below the costal margin is often used to
monitor spleen size, and of course a similar measurement could also be
obtained on sonography.
Conventional sonography is a well-established, widely used, and relatively
inexpensive means of assessing the spleen without ionizing radiation. A study
by Rosenberg et al. [9] found
that a simple measurement of splenic length was accurate as a guide to spleen
size. The authors proposed setting the upper normal limit of splenic length at
12 cm for girls 15 years or older and at 13 cm for boys 15 years or older.
This study [9] and another by
Dittrich et al. [5]. found that
there was an approximately linear increase in spleen size, as measured on
sonography, in the course of development in the pediatric population and that
spleen size correlated best with the body height. A third study of the
pediatric population by Konus et al.
[10] with 307 subjects also
found that height correlated best with spleen length (r = 0.88),
although their tallest individual was only 68 inches (173 cm), which is of
course much shorter than our study population. In a study of adults, Frank et
al. [11] used conventional
sonography to evaluate 793 healthy patients (17-82 years) and found that 95%
of patients had a splenic length of less than 11 cm, a width (transverse
dimension) of less than 7 cm, and a thickness of less than 5 cm. Niederau et
al. [12] studied 915 healthy
subjects using sonography and found the mean longitudinal and transverse
diameters of the spleen to be 5.8 ± 1.8 cm and 5.5 ± 1.4 cm,
respectively [12]. These
dimensions are much smaller than those of other studies because the authors
did not measure the maximal length of the spleen as authors in other studies
have, but rather the true superior-to-inferior length. This study further
found that spleen size did correlate weakly with height in the general
population.
Sonographic measurements of splenic length have also been correlated with
actual spleen dimensions at autopsy
[13]. A study by Loftus et al.
[13] on 30 cadavers found a
clear linear relationship between a sonographic measurement of splenic length
and the actual length, volume, and weight as measured at autopsy. The
Pearson's product moment correlation coefficient for maximal sonographic
length and the actual length was 0.831 (p < 0.001). They suggested
that a simple single sonographic measurement of length could be used for
routine work, reserving the more complex volumetric measurement (splenic area
or index) for problematic cases. This position is further bolstered by another
study that showed good correlation between CT volume and splenic length
measured on sonography (r = 0.86, p < 0.001)
[14]. The preponderance of
evidence, then, indicates that a simple measurement of spleen length is a
practical and reasonably accurate estimate of spleen size.
What is the true risk of splenic injury and bleeding for a young athlete
recovering from infectious mononucleosis? With splenomegaly from
mononucleosis, splenic rupture is reported to occur in one to two patients per
1,000 affected individuals
[15] and usually takes place
between days 4 and 21 after the onset of illness, when the splenic capsule is
heavily infiltrated with lymphocytes
[3,
16,
17]. In a 40-year Mayo clinic
review of 8,116 patients with infectious mononucleosis, only nine had splenic
rupture. Although the most vulnerable period is during weeks 2-4 of illness,
rupture can occur as early as 3 days or as late as 2 months
[3]. These statistics are not
drawn from a population of athletes engaged in vigorous contact sports, but
the risk of splenic rupture is relatively low even when the spleen is large.
This risk is probably much less still with normal spleen sizes.
There are a few limitations to this study. Our study population included
only tall healthy athletes. It seems likely that the data from this study
would also apply to tall individuals who are not athletes, but we cannot be
certain. A larger study that includes nonathletes might improve the precision
of our estimates and also the generalizability of the data.
In conclusion, the writing of guidelines for return to play must take into
account revised standards of spleen size. Our data support adjusting the upper
limit of the normal range for spleen length to avoid the false-positive
diagnosis of splenomegaly in very tall patients. Certainly, the health and
safety of these young athletes must remain the paramount concern, but also it
would be unfortunate to bench a healthy athlete because inappropriate
standards are applied to the interpretation of sonographic measurements,
especially considering that the risk of splenic rupture is likely quite small
after recovery from the acute period of splenomegaly with infectious
mononucleosis.
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Abstract
Introduction
