Thymus Laterality in Children
The provided evidence does not contain specific data on the percentage of children with left-sided thymus positioning.
Normal Thymic Anatomy in Pediatric Populations
The thymus in healthy children exhibits predictable anatomical characteristics, but the evidence does not address laterality percentages:
Morphological Features by Age
In children younger than 5 years:
- The thymus demonstrates a quadrilateral shape with biconvex lateral contours 1
- The gland is readily visualized on imaging in 94% of children aged 2-8 years 2
In older children and adolescents:
- The thymus assumes a triangular configuration with straight lateral margins 1
Bilateral Thymic Lobes
The thymus consists of two lobes with distinct characteristics 2:
Right lobe:
- Mean anteroposterior dimension: 1.4 cm
- Mean longitudinal dimension: 2.5 cm
- Typically displays an inverted teardrop shape on longitudinal imaging 2
Left lobe:
- Mean anteroposterior dimension: 1.4 cm
- Mean longitudinal dimension: 2.9 cm (slightly larger than right)
- Demonstrates either triangular or sickle-shaped morphology 2
Clinical Implications
The thymus is a bilateral organ that normally extends across the midline in the anterior mediastinum. The question of "left-sided" thymus may refer to ectopic thymic tissue, which occurs in various cervical locations in rare cases 3. Among 115 ectopic thymic lesions identified, locations included thyroid involvement (44%), central neck (29%), mediastinal extension (18%), and submandibular region (8%) 3.
The concept of a purely "left-sided" thymus as a normal variant is not supported by the available evidence, as the thymus is inherently a bilobed midline structure with both right and left components.