Splenic Index
The splenic index is a calculated measurement used to quantify splenic size by multiplying three orthogonal dimensions of the spleen: craniocaudal length × width × thickness (measured in centimeters), with a normal upper limit of ≤480 cm³ 1, 2.
Definition and Calculation
The splenic index provides a volumetric assessment of the spleen using the formula:
Splenic Index = Craniocaudal Length (cm) × Width (cm) × Thickness (cm)
This multidimensional measurement correlates significantly better with actual splenic volume (r = 0.95) compared to single-dimension measurements 3.
Normal Range
For reference, individual dimension upper limits in normal spleens are:
Clinical Applications
Portal Hypertension Assessment
The splenic index has particular clinical utility when combined with other parameters to assess clinically significant portal hypertension (CSPH) in patients with compensated advanced chronic liver disease:
Liver Stiffness-Spleen Diameter to Platelet Ratio Score (LSPS) is calculated as:
- LSPS = Liver Stiffness (kPa) × [Spleen Size (mm) / Platelet Count (G/L)]
- LSPS >2.06 diagnoses CSPH with 92% sensitivity and 90% specificity 1
- LSPS >3.21 rules in/out varices with 81% sensitivity and 86% specificity 1
This combined approach is endorsed by the 2021 EASL guidelines as superior to using spleen size alone, which is "sensitive but nonspecific" for portal hypertension 1, 4.
Measurement Technique
CT imaging is the preferred modality for accurate splenic index calculation, as it allows precise measurement of all three dimensions 2, 3. The splenic index calculated from CT measurements shows excellent correlation with actual splenic volume and is more reliable than single-dimension measurements or ultrasound-based assessments 2.
Important Caveats
- Splenomegaly alone (index >480) is a sensitive but nonspecific sign of portal hypertension and cannot diagnose CSPH independently 4
- Always combine splenic measurements with platelet count and liver stiffness when evaluating for portal hypertension to improve diagnostic accuracy 1, 4
- Single coronal oblique length >12 cm has 97.8% sensitivity but only 34.1% specificity for splenomegaly, making it useful for screening but requiring confirmation with full splenic index calculation 2
The splenic index should be routinely reported in imaging studies, particularly in patients with suspected liver disease, as it provides quantitative data that, when integrated with laboratory parameters, significantly improves risk stratification for portal hypertension and variceal bleeding 1, 4.