Spleen Ultrasound: Normal Size, Measurements, and Splenomegaly

The spleen is one of the most commonly measured organs in abdominal ultrasound, yet it's also one of the most frequently eyeballed rather than formally measured. A borderline spleen that gets called "mildly prominent" without a number is a missed opportunity — both clinically and for the interpreting physician writing the report. Here's how to measure it right and what to do with the result.

Normal Spleen Size

The spleen is measured in its longest craniocaudal dimension on a coronal or oblique coronal image, taken at the splenic hilum level. Normal values by major consensus:

Measurement	Normal Upper Limit
Length (craniocaudal)	≤12 cm
Width (AP diameter)	≤7 cm
Thickness	≤4 cm
Volume (estimated)	≤314 mL

For practical purposes, 12 cm is the threshold most radiologists and clinicians use. A spleen measuring 12.1 cm gets flagged; one measuring 11.9 cm does not. That said, splenic size correlates with patient body habitus — a 6-foot-tall man may have a physiologically larger spleen than a small woman, so clinical correlation always applies.

How to Measure

Patient Position

Use the right lateral decubitus (left side up) position whenever possible. This brings the spleen away from the ribs and uses the left kidney as an acoustic window. Many sonographers also scan from a posterior intercostal approach with the patient in right lateral decubitus — this frequently provides the best long-axis view.

Probe Selection

Start with a curved low-frequency probe (2–5 MHz). In thin patients, a linear probe may give superior resolution for surface evaluation. In obese patients or those with significant bowel gas, lower frequencies (2–3 MHz) penetrate better.

Getting the Long Axis

The key is finding the true long axis of the spleen — the image where the organ appears largest. The spleen's long axis is oblique, running roughly from the upper left to the lower right in most patients. Rock and angle the probe until you see the maximum length, confirming the tips (upper and lower poles) are both sharp and fully visualized.

Common error: Cutting through the spleen at an angle produces a shorter apparent length. If the poles look blunt or truncated, you're not at the true long axis. Adjust until both poles are sharply defined.

Measurement Technique

Place calipers at the outer edges of both poles, following the long axis of the organ — not a straight horizontal line. The measurement should trace the natural curvature if needed, or be placed along the maximum linear dimension.

Document:

1. Craniocaudal length (most important)
2. AP diameter (from the hilum image)
3. Any focal abnormalities (cysts, masses, infarcts)

Splenomegaly: Grading

When the spleen exceeds normal limits, most practices use a simple grading system:

Grade	Length
Mild splenomegaly	12–15 cm
Moderate splenomegaly	15–20 cm
Massive splenomegaly	>20 cm

A spleen measuring >20 cm is clinically significant and often symptomatic — patients may describe early satiety, left upper quadrant fullness, or pain. Massive splenomegaly can extend across the midline to the right lower quadrant and should be fully documented, even if the full extent isn't measurable in a single image.

Sonographic Appearance: Normal vs. Abnormal

Normal Spleen

• Homogeneous, medium-level echogenicity
• Slightly more echogenic than the left kidney, slightly less echogenic than the liver
• Smooth capsule
• Splenic vein visible at the hilum, flowing toward the portal vein

Abnormal Findings to Document

Focal hypoechoic lesions:

• Infarcts (often wedge-shaped, peripheral, pointing toward hilum)
• Lymphoma deposits (multiple round hypoechoic nodules)
• Abscesses (irregular walls, internal debris)
• Metastases (less common than in liver)

Diffuse changes:

• Increased echogenicity throughout → hemosiderosis, sarcoidosis
• Heterogeneous echotexture → lymphoma, infiltrative disease

Accessory spleen (splenunculus):

• Small, round, homogeneous nodule near the splenic hilum
• Same echogenicity as the spleen — important not to mistake for lymphadenopathy
• Present in up to 30% of the population, almost always incidental

Perisplenic fluid:

• Free fluid around the spleen suggests ascites, trauma, or splenic rupture (in the right clinical context)

Common Causes of Splenomegaly

Splenomegaly itself is a finding, not a diagnosis. Your role is to measure it accurately and note any associated findings that suggest a cause.

Portal Hypertension

The most common cause in clinical practice. Look for:

• Splenomegaly (often moderate)
• Dilated splenic vein (>1 cm at hilum) or portal vein (>1.3 cm)
• Varices near the splenic hilum or splenorenal ligament
• Ascites
• Altered liver echotexture (coarsened, nodular surface in cirrhosis)
• Reversed or sluggish portal vein flow on Doppler

Hematologic Conditions

• Lymphoma / leukemia: Often massive splenomegaly, may show focal hypoechoic lesions
• Myeloproliferative disorders: Homogeneous massive splenomegaly without focal lesions
• Hemolytic anemias (sickle cell, thalassemia): Sickle cell classically causes autosplenectomy — the spleen may be small and echogenic (infarcted), not enlarged

Infections

• Infectious mononucleosis: Young patients, mild-to-moderate splenomegaly, often tender
• Malaria: Endemic areas; can cause massive splenomegaly
• Endocarditis, sepsis: Mild splenomegaly common

Infiltrative Disease

• Sarcoidosis, amyloidosis, Gaucher disease — typically diffuse homogeneous enlargement

What to Include in Your Report

A complete splenic evaluation documents:

1. Size — give the craniocaudal measurement in centimeters, always
2. Echotexture — homogeneous or heterogeneous
3. Focal lesions — size, location, echogenicity
4. Splenic vein — diameter at the hilum, flow direction on Doppler if assessed
5. Incidental findings — accessory spleen, perisplenic fluid

Avoid "spleen appears normal" without a measurement. A number is always more defensible than an impression, especially for a borderline organ.

Clinical Pearls

• A ruptured spleen from trauma may not look enlarged — look for perisplenic hematoma (hyperechoic fluid acutely, becoming complex over hours), subcapsular collections, and parenchymal lacerations
• The spleen is one of the most vascular organs in the body — penetrating trauma or even blunt trauma in an enlarged spleen can cause life-threatening hemorrhage
• Spontaneous splenic rupture (from mononucleosis or hematologic disease) is rare but real — if a patient has a very large spleen and pain, document carefully and communicate urgently
• In portal hypertension, splenomegaly may precede ascites or esophageal varices — it's one of the earliest sonographic signs

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All measurements reflect current published guidelines from ACR, AIUM, and standard abdominal ultrasound references. Clinical decisions should involve the interpreting physician.