Splenomegaly on Ultrasound: Longitudinal and Splenic Index Thresholds
Threshold Values for Longitudinal Length
The normal size of the spleen significantly depends on the patient's age, sex, and body habitus; however, traditionally, a numerical threshold of 12 cm is used (ExpertDDx: Abdomen and Pelvis, 3rd Edition). According to the Textbook of Diagnostic Sonography (9th Edition), splenomegaly in an adult is diagnosed with a spleen length of more than 13 cm, and in a child, when exceeding the norm for the respective age. In Diagnostic Ultrasound: Abdomen & Pelvis (2nd Edition), splenomegaly is also considered at a length >13 cm.
Normally, the spleen length usually exceeds the kidney length; when enlarged, the distal pole (tip) of the spleen overlaps the lower pole of the kidney.
Age-Related Norms for Longitudinal Length
The upper limit of normal spleen length varies from 6.0 cm in children under 3 months to 12 cm in children over 12 years (Textbook of Diagnostic Sonography, 9th Edition).
| Age Group | Upper Length Limit |
|---|---|
| Infants <3 months | 6.0 cm |
| Children over 12 years | 12 cm |
| Adults | >13 cm — splenomegaly |
Additional Measurements and Splenic Index
In addition to longitudinal length, additional measurements are used: thickness >5 cm and width >8 cm (Diagnostic Ultrasound: Abdomen & Pelvis, 2nd Edition). The splenic index is calculated as the product of length, thickness, and width (in cm). According to ExpertDDx, an index >480 suggests splenomegaly; according to Diagnostic Ultrasound, normal index values are 120–480 cm³, and splenomegaly is considered at an index >500 cm³.
Examination Technique
The left upper quadrant is visualized by carefully moving the transducer between the intercostal spaces to obtain images of the left kidney, spleen, and diaphragm. A sector transducer may fit better between the ribs than a larger convex transducer. The left dome of the diaphragm and pleural cavity should be assessed.
Common Causes of Splenomegaly
One of the most common causes in everyday practice is cirrhosis with portal hypertension: the morphology of the cirrhotic liver (nodularity of the capsule, groove widening, caudate lobe hypertrophy) with stigmata of portal hypertension (varices, ascites, mesenteric edema). Other causes include portal or splenic vein thrombosis, hematological disorders (polycythemia, leukemia, myelofibrosis, hemoglobinopathies), infectious-inflammatory processes (mononucleosis, hepatitis, HIV, malaria, sarcoidosis), mass lesions (cysts, lymphoma, metastases), and infiltrative diseases (Gaucher's disease, amyloidosis, hemosiderosis).
Frequently asked questions
What longitudinal length is considered the threshold for splenomegaly in adults?
The traditional cut-off is 12 cm (ExpertDDx); the Textbook of Diagnostic Sonography and Diagnostic Ultrasound indicate splenomegaly at a length of more than 13 cm in adults.
How is the splenic index calculated and what is its threshold?
Index = length × thickness × width (cm). Normal is 120–480 cm³; splenomegaly at an index >480 (ExpertDDx) or >500 cm³ (Diagnostic Ultrasound).
What additional measurements are used besides length?
Thickness greater than 5 cm and width greater than 8 cm (Diagnostic Ultrasound: Abdomen & Pelvis, 2nd Edition).
What are the norms for longitudinal length in children?
From 6.0 cm in infants under 3 months to 12 cm in children over 12 years (Textbook of Diagnostic Sonography, 9th Edition).
What most commonly causes splenomegaly in practice?
One of the most common causes is cirrhosis with portal hypertension; also hematological, infectious-inflammatory, infiltrative diseases, and mass lesions.