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Sonography of the thymus in healthy children: frequency of visualization, size, and appearance
1Department of Radiology, St. George's Hospital, London, United Kingdom.
Insights
The normal thymus is easily visualized on ultrasound in most children aged 2-8 years. This study details its typical size, shape, and echogenicity for accurate pediatric imaging.
Area of Science:
- Pediatric Radiology
- Diagnostic Ultrasound
- Anatomy
Background:
- The thymus is a crucial primary lymphoid organ.
- Accurate sonographic assessment of the thymus is important for pediatric health evaluations.
- Previous studies suggested limited visualization of the thymus in older children.
Purpose of the Study:
- To determine the frequency of thymus visualization on sonograms.
- To measure the size and describe the sonographic appearance of the normal thymus.
- To evaluate thymus characteristics in children aged 2-8 years.
Main Methods:
- Fifty asymptomatic children aged 2-8 years underwent ultrasound.
- Scans were performed using a 7.5-MHz probe via suprasternal and parasternal windows.
- Thymus dimensions and echogenicity were measured and compared to liver and thyroid echogenicity.
Main Results:
- The thymus was completely visualized in 94% of children.
- Mean dimensions were approximately 1.4 cm (anteroposterior) and 2.5-2.9 cm (longitudinal).
- The thymus echogenicity closely matched the liver, with characteristic shapes observed.
Conclusions:
- The normal thymus is readily visualized on ultrasound in most children up to 8 years old.
- This finding extends the age range for easy thymus sonographic detection.
- Sonography is a reliable method for assessing the normal thymus in pediatric patients.
Objective:
The purpose of this study was to determine the frequency of visualization, the size, and the sonographic appearance of the normal thymus on sonograms of children 2-8 years old.
Subjects And Methods:
Fifty children without symptoms referable to the thymus were scanned through the suprasternal notch and parasternal windows with a Diasonics DRF 100 scanner and a 7.5-MHz probe. The anteroposterior and longitudinal dimensions of the thymus were measured and the echogenicity of the thymus was subjectively assessed and compared with the liver and thyroid gland. No change was made in the time-gain compensation or overall gain settings.
Results:
The thymus was completely visualized and measured in 47 (94%) of the 50 patients. The mean anteroposterior and longitudinal measurements were 1.4 and 2.5 cm, respectively, for the right lobe and 1.4 and 2.9 cm, respectively, for the left lobe. On longitudinal sonograms, the right lobe tended to have an inverted teardrop shape whereas the left lobe was either triangular or sickle shaped. The mean absolute dimensions of the thymus changed little with age, although the number of children in each age group was small. The internal echogenicity of the thymus most closely resembled that of the liver.
Conclusion:
The thymus is clearly and easily visualized on sonograms in the majority of children 2-8 years old, a much later age than reported previously.