Variation of Normal Thymic Veins With Age And Gender in a Large Series of Subjects on Enhanced Multidetector Computed...

The thymic veins are small vessels located in the anterior superior mediastinum, and thymic tissue undergoes physiological degeneration with age. Multidetector computed tomography (MDCT) with isotropic resolution allows comprehensive visualization of small mediastinal vessels. However, large-sample studies describing normal thymic veins using contrast-enhanced MDCT remain lacking. This study aimed to evaluate the morphologic features of normal thymic veins on venous-phase enhanced MDCT and to analyze their distribution patterns according to age group, gender, and laterality in a large patient cohort.

The enhanced MDCT images of the chest were retrospectively collected from 289 cases. First, the collected cases were divided into four age groups; second, the thymic veins shown in the venous phase were classified and measured by three-dimensional visualization using MPR and VR techniques; lastly, statistical analysis was performed to analyze the relationship between the occurrence rate of the different types of thymic veins and age groups, genders as well as the relationships between the inner diameter and sides. The inter-observer agreement was statistically analyzed.

The manifestations of the thymic vein could be divided into three types by enhanced MDCT. The thymic vein drained upward into the inferior thyroid vein and the left brachiocephalic vein. The occurrence rate of the continuous, the intermittent, the unrecognized types were 63.0%, 21.8%, and 15.2%, respectively. 9.3% was the incidence rate of the intermediate vein among the continuous type. The display rates of the continuous, the intermittent, and the unrecognized in the four age groups (0-20), (20-40), (40-60), and >60 years old) were 8.3%, 0.0%, 91.7%;71.1%, 5.3%, 23.7%;61.4%, 35.6%, 3.0%; and 72.7%, 26.1%, 1.1%, respectively. Statistically significant difference between the occurrence rate of different types and age groups was proved by the Chi-squared test (P<0.001). No significant difference between the occurrence rate of different types and genders by the Chi-squared test (P=0.07). The range of diameters of the continuous type of left, right thymic veins was (1.90 ± 0.52 mm,2.04 ± 0.6 mm), respectively, and the diameter of the right was larger than the left by t-test. Both the occurrence rates of the continuous and those of the intermittent increased with age in the line graph, while the occurrence rates of the unrecognized type decreased with age. High agreements were demonstrated by the intra-class correlation coefficient.

Thymic veins show characteristic morphological changes with advancing age, likely related to the physiological involution of the thymus gland. Young individuals demonstrate very low visualization rates, whereas older age groups show predominantly continuous or intermittent visualization. MDCT with three-dimensional reconstruction enables reliable depiction and classification of normal thymic veins, which may serve as an anatomical reference for mediastinal imaging interpretation.

Most thymic veins still existed despite the degeneration of the thymus in a large-sample MDCT study. A variety of drainage pathways into the inferior thyroid vein and left brachiocephalic vein were displayed, and the occurrence rate of different venous drainage patterns varied with age. Preoperative assessment of the thymic veins would help reduce intraoperative bleeding in the anterior superior mediastinum.