Splenomegaly refers to enlargement of the spleen. The upper limit of the normal adult splenic length is traditionally cited at 12 cm, but lengths upwards of 14 cm can be seen in normal, taller males 7.
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Terminology
Massive splenomegaly is variably defined, including when the spleen is 5 standard deviations above the mean normal volume (~943 cm3) 4, heavier than 1.0 kg 5 or 1.5 kg 8, >14.5 cm true craniocaudal measurement on coronal CT 4, >15 cm on clinical exam 8, or at/below the umbilicus, extending into the pelvis and/or across the midline 4,8.
Pathology
Etiology
The causes of splenomegaly are protean, and can be thought of under several headings 3,8:
hematological disease
hemodynamic
infectious
storage diseases/metabolic/infiltrative disorders
neoplastic (non-hematologic)
traumatic
Hematological disease
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thalassemia (including beta-thalassemia major)
sickle cell disease with splenic sequestration (in young patients before developing autosplenectomy)
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neoplastic/proliferative/redistribution of hematopoiesis
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myeloproliferative neoplasms
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lymphoma or chronic lymphoid neoplasms
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Hemodynamic
cirrhosis: portal hypertension (common)
congestive splenomegaly (Banti syndrome)
Infection
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viral
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bacterial
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fungal
histoplasmosis (common)
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parasitic disease
malaria* (hyperreactive malarial splenomegaly syndrome or tropical splenomegaly syndrome)
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rickettsial
typhus
Storage diseases/metabolic/infiltrative disorders
Neoplastic (non-hematologic)
Trauma
Connective tissue disorders
Massive splenomegaly
It is sometimes helpful to consider those etiologies that may cause the spleen to grow especially large as a separate group 3,8:
thalassemia (including beta-thalassemia major)
myeloproliferative neoplasms
lymphomas/chronic lymphoid neoplasms
cirrhosis with portal hypertension 4
Radiographic features
The shape and orientation of a spleen make accurate linear measurement difficult. Since single length measurements are relatively inaccurate many volume-based approaches have been proposed. True volumetry is the most accurate but is rarely feasible in routine clinical practice.
Ultrasound
On sonographic assessment, a length of 12 cm is generally considered the upper limit of normal 15.
On ultrasound the prolate ellipsoid formula is used most commonly 13:
spleen volume (cm3) = 0.52 × length × anteroposterior dimension × width (cm)
A modified formula has been proposed to improve accuracy 14:
spleen volume (cm3) = 0.524 × width × thickness × (maximum length + craniocaudal length) / 2
CT
Single splenic measurements can be used to identify splenomegaly:
width (largest AP axial measurement) >10.6 cm 15
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craniocaudal length
>9.5-10.5 cm for splenomegaly 4,15
>14.5 cm for massive splenomegaly 4
coronal oblique length >12 cm
The splenic index was first proposed to express splenic volume 10:
splenic index = length × width × thickness (cm)
The normal range of the index is 120-480 and this is considered the most reliable measurement for splenomegaly 15. Since the index does not have a unit, other formulas have been proposed for estimating splenic volume on cross-sectional imaging 5:
spleen volume (cm3) = 30 + 0.58 × craniocaudal length × diameter × thickness (cm)
Where:
length is defined as the craniocaudal distance between the first and last slices in the axial plane where the spleen is depicted
diameter is the largest measurable long axis distance in the axial plane
thickness is the largest perpendicular dimension to the diameter in the axial plane
The normal range of the estimated volume in healthy individuals with this formula is 107.2-314.5 cm3 (mean: 214.6 cm3) 5.
Practical points
The normal spleen size for any individual is substantially influenced by demographic factors, sex, and body habitus, e.g. a study using volumetry found a 236.89 ± 77.58 cm3 average normal spleen size, whilst thresholds of 314.47 and 430.84 cm3 were determined for mild and massive splenomegaly respectively 11. In contrast, a study done by Japanese researchers has found much lower values in a different patient population for average spleen volume (112 cm3) and normal range (32-209 cm3) 12. Furthermore, it has been also shown that normal spleen size is influenced by sex and body habitus, with men, and taller or heavier individuals having longer and larger spleens 13.
External links
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splenic index and volume calculator for CT, US, and MRI measurements - Rad at Hand
with expected upper limits of normal for splenic length and volume in adults
If any of these links are broken or for other problems and questions, please contact editors@radiopaedia.org.
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