Spleen on ultrasound: normal size and echocardiogram

The spleen is a parenchymatous organ located in the left upper quadrant with a thin capsule and a homogeneous, fine-grained echostructure. Ultrasound allows for rapid and safe assessment of its size, contours, echogenicity, hilum vessels, and structural variations. This method is recommended as the standard for initial imaging when organ size is in doubt, portal hypertension, systemic blood diseases are suspected, and for follow-up. [1]

The normal spleen in adults is wedge-shaped, has smooth contours, and a moderately homogeneous parenchyma. Echogenicity is usually comparable to or slightly higher than that of the liver, and is equal to or slightly hyperechoic relative to the renal cortex when assessed at the same depth. Maintaining these landmarks is important because relative comparisons help detect early diffuse changes. [2]

The spleen length in most adults is approximately 12-13 cm, but the upper limit varies with height and gender. In tall and athletic individuals, a normal length can reach 14 cm without signs of pathology, so interpretation should take into account somatometric characteristics rather than relying on a single, rigid threshold. [3]

Current guidelines emphasize standardization of measurements, documentation of key sections, and, when necessary, the use of splenic hilum Doppler ultrasonography. This improves reproducibility and reduces the incidence of false positives in routine practice. [4]

How to scan correctly and what to record

Optimal acoustic windows are intercostal approaches along the posterior and midaxillary lines in the supine or right lateral position, with inspiration to lower the diaphragm. The protocol includes longitudinal and transverse sections through the splenic hilum, measuring the length along the maximum craniocaudal axis and the thickness at the widest point. All measurements are performed on sections where the capsule is clearly visualized. [5]

The report documents the shape and contour, capsule, parenchymal homogeneity, focal lesions, the number and diameter of accessory spleens, the condition of the hilum, the caliber of the splenic vein, and the nature of blood flow according to Doppler. In the presence of gas shielding, it is recommended to vary the intercostal windows and focal depth to avoid underestimation of size. [6]

In children, spleen length is measured as the maximum distance between the largest superomedial and inferolateral poles on a coronal longitudinal section, preferably through the hilum. This is crucial for comparability with age tables and for dynamics. [7]

To quantify volume, an ellipsoid formula is used: length is multiplied by width and thickness, then by a coefficient of 0.523. This approach is convenient for monitoring hematological and portal conditions, when volume dynamics are more informative than single length. [8]

Normal echocardiogram: what to look for

The spleen parenchyma is normally homogeneous, moderately echogenic, with a thin hyperechoic capsule line. Compared to the liver, the spleen often appears equal to or slightly more echogenic, and when compared to the kidney, its echogenicity is equal to or slightly higher than that of the cortex at the same depth. Significant deviations require comparison with clinical and biochemical findings. [9]

The vascular pattern of the hilum is clearly visible on color Doppler ultrasound, which helps distinguish vascular anomalies and lesions. The presence of uniform blood flow through the splenic artery and vein without signs of turbulence and with normal vessel caliber is a sign of normal organ hemodynamics. [10]

Anatomical variations within the normal range are common. The most common is an accessory spleen: a rounded nodule typically up to 1-3 cm, isoechoic to the parenchyma, and associated with the hilum. Correct recognition of this normal variant prevents unnecessary examinations. [11]

Sizes: How to interpret them in adults

In most adults, the normal spleen length does not exceed 12-13 cm, and its thickness is approximately 3-4 cm. Height and gender play a significant role, so tall individuals may have a higher upper limit. Interpretation based on a single threshold without taking somatometry into account increases the risk of false overdiagnosis. [12]

The splenic vein at the hilum typically has a diameter of less than 10 mm at rest and exhibits moderate respiratory dilation. Significant dilation or loss of variability requires exclusion of portal hypertension and thrombosis with evaluation of the portal vein and splenoportal system.[13]

For clinical monitoring, calculating volume using the ellipsoid formula is convenient, especially for systemic blood diseases and portal conditions. Volume correlates with anthropometry and provides a more stable reference point than a single length, at variable scanning angles. [14]

Norms in children: what is considered typical

In newborns and children, spleen length increases with age and growth. Age-specific tables and percentile curves are used, where the assessment is based on the maximum longitudinal length through the hilum. This approach allows one to distinguish true enlargement from the normal range in tall and rapidly growing children. [15]

In early infancy, the liver is often more echogenic than the spleen, and the renal cortex in newborns may appear more echogenic. These age-related characteristics are taken into account when comparing organs to avoid overdiagnosis of diffuse changes. [16]

If in doubt, a repeat examination by the same specialist using the same measurement technique is preferable. Consistent use of the same reference points minimizes interobserver variability and improves dynamic assessment. [17]

Dopplerography: What is considered normal?

The resistive index in the splenic artery branches in healthy individuals is typically below 0.7, with no signs of high peripheral resistance and a stable spectrum. Significant deviations are considered in the context of overall portal hemodynamics and systemic factors. [18]

The splenic vein is characterized by laminar hepatopetal blood flow with respiratory variability in diameter. The absence of variability, marked dilation, or signs of thrombosis warrant further examination of the portal system and a coagulogram. [19]

Normal variations and common pitfalls

Accessory spleens occur in a significant proportion of the population and are visualized as isoechoic rounded nodules, most often in the hilum. Misinterpretation can lead to unnecessary biopsies or surgical interventions, so the relationship with the splenic vessels and typical vascularization are always assessed. [20]

Measurement error is possible with an oblique cut, when the length is overestimated due to a projection outside the true long axis. To avoid this, simultaneous visualization of both poles and a smooth capsule is achieved, and the result is confirmed with an alternative intercostal window. [21]

Costal shadows and flatulence can obscure the capsule and create the appearance of an irregular contour. In such cases, changing the angle, applying compression with the transducer through the intercostal spaces, and adjusting the gain without excessive enhancement, which creates a pseudogranular appearance, can help. [22]

When to recommend further imaging

If clinical and ultrasound findings are inconsistent, or if lesions are ambiguous or vascular complications are suspected, supplementation with contrast-enhanced ultrasound, computed tomography, or magnetic resonance imaging is warranted. The choice of method is determined by the objective, availability, and need for staging. [23]

In children and pregnant women, ultrasound techniques are preferred when vascular characteristics need to be clarified. If splenoportal thrombosis is suspected, Doppler criteria and comparison with laboratory data are crucial. [24]

Tables

Table 1. Standard for measuring the spleen using ultrasound

Protocol element	What to do
Plane	Longitudinal and transverse sections through the splenic hilum
Length	Maximum craniocaudal axis with clear visualization of the capsule
Thickness and width	At the widest points on the orthogonal section
Documentation	Save key cuts with caliper and signature
Source: European guidelines for ultrasound of the spleen. [25]

Table 2. Normal ultrasound echocardiogram of the spleen

Sign	Expected norm
Circuit and capsule	Smooth, capsule thin hyperechoic line
Echostructure	Homogeneous, fine-grained
Comparison with the liver	Equal or slightly hyperechoic
Comparison with the renal cortex	Equal or slightly hyperechoic at the same depth
Source: reviews of normal echostructure. [26]

Table 3. Spleen sizes in adults: how to interpret

Indicator	Typical range in healthy individuals	Comment
Length	Up to 12-13 cm, for tall ones up to 14 cm	Assess based on height and gender
Thickness	About 3-4 cm	Varies with scanning angle
Splenic vein	Up to 10 mm at the gate, with respiratory variability	The absence of variability requires further examination.
Source: reference books on ultrasound and vascular norms. [27]

Table 4. Spleen volume

What to count	How to count	Where applicable
Volume index	Length x width x thickness x 0.523	Dynamic monitoring in hematological patients
Advantages	Less dependence on angle, convenient for comparison	When repeating studies in one laboratory
Restrictions	Errors due to imprecise orthogonality, strong deformation	Requires a reproducible protocol
Source: studies on volumetric assessment of the spleen. [28]

Table 5. Children: spleen length estimation

Age group	Approach to measurement	Interpretation
Newborns and infants	Maximum longitudinal length through the gate	Comparison with age tables and percentiles
Preschoolers and schoolchildren	The same technique, in dynamics with one operator	Growth-dependent norms, avoid hard thresholds
Teenagers	Taking into account height and gender	Check the boundary values again
Source: Reference pages on norms in children. [29]

Table 6. Dopplerography of the splenic vessels

Parameter	Norm	Comment
Resistive index in artery branches	Typically < 0.7	It is estimated on the section of the straight vessel behind the gates
Blood flow in a vein	Laminar, with respiratory variability of diameter	Significant expansion or lack of variability is a reason to look for portal changes
Source: Portal hemodynamics guidelines and educational materials. [30]

Table 7. Normal variants and how to distinguish them from pathology

Option	Signs	Tips
Accessory spleen	A rounded node 1-3 cm, isoechoic to the parenchyma, often at the hilum	Typical vascularization and connection with the splenic vessels are observed.
Lobular margin	Small contour notches, stable over time	Not accompanied by changes in the parenchyma
Source: Clinical reviews and atlases on the spleen. [31]

Common Interpretation Errors and How to Avoid Them

Overestimation of the length with an oblique view leads to false overdiagnosis. Measurements should be confirmed with an alternative intercostal window, and a true long axis with even visualization of both poles should be achieved. [32]

Incorrect comparison of organ echogenicity at different depths can create the illusion of diffuse changes. Comparison of the liver, spleen, and renal cortex is only valid at the same depth and settings. [33]

Mistaking an accessory spleen for a pathological node leads to a cascade of unnecessary examinations. The node is isoechoic to the parenchyma and has a blood supply similar to that of splenic tissue; if in doubt, additional signs and dynamics are used. [34]