Ultrasound of the thymus gland is a non-invasive examination of the thymus using ultrasound waves. Allows you to get information about the size, shape, location and structure of the thymus gland. It is usually performed in childhood to detect thymomegaly. In older children, indications for scanning are frequent severe colds, unexplained subfebrility and allergic reactions. Adult patients are prescribed a study if they suspect thymoma, T-cell lymphoma, other types of thymus neoplasia and some rare syndromes (for example, Di Georg syndrome).
Ultrasound of the thymus belongs to the category of screening studies. It can be carried out both as a preventive examination, and when special indications appear indicating a violation of the work of the organ. Prophylactically, ultrasound can be prescribed to children under the age of 1 year. Older children are recommended to conduct a planned study during the period of registration in a preschool institution. As indications for an unscheduled ultrasound of the thymus gland in children, more than 10 colds are considered during the year and a large number of complications (bronchitis, sinusitis, pneumonia) that have arisen against the background of acute infections.
The study is also carried out in the presence of pronounced diathesis, dysbiosis, pollinosis, urticaria, bronchial asthma and predisposition to allergic reactions. Indications are a prolonged or repeated increase in temperature to subfebrile digits and an increase in lymph nodes. Significant thymomegaly can cause compression of the vagus nerve, vascular bundle and neighboring organs, so children are referred for ultrasound of the thymus with copious regurgitation, heavy noisy breathing, whooping cough, cardiac arrhythmias and the appearance of a vascular mesh on the skin of the chest. Adults are prescribed the procedure when clinical or radiological signs of thymus pathology appear. There are no contraindications.
Special preparation for the study is not required. Before ultrasound, it is necessary to determine the weight of the child for the subsequent calculation of the normal mass of the thymus gland, taking into account the parameters of the patient’s body. Parents are advised to choose easily removable clothes for the child and prepare napkins or a small towel to remove gel residues from the skin. The quality of diagnostic data directly depends on the behavior of the child during the procedure, so experts advise parents to calm the baby in advance and try to create a favorable emotional atmosphere. You can take a distraction toy with you.
Methodology of conducting
For newborns, ultrasound examination is performed in a position on the back, placing a small roller under the neck. When signs of anxiety appear in young children, the scan is performed in a lying position or sitting on the parent’s lap. Patients older than two years are examined in a standing position. During the procedure, a water-based gel is applied to the baby’s chest, ensuring that there is no air gap between the sensor and the patient’s skin. Information is sent from the sensor to the monitor.
Ultrasound diagnostics scans in the transverse and longitudinal planes, determines the localization, size and shape of the organ, evaluates the contours, echogenicity and uniformity of the thymus structure, and also identifies additional inclusions (if any). The duration of the procedure is 10-15 minutes. After its completion, the gel is removed from the baby’s chest. Then the specialist performs special calculations to evaluate the results of the study.
Interpretation of results
The normal thymus is an organ with an average echogenicity, smooth contours and a homogeneous structure. The gland is clearly delimited from other anatomical formations and soft tissues of the anterior mediastinum. The posterior border of the organ is smooth. In the presence of tumors of the thymus gland, ultrasound reveals areas with altered echogenicity, heterogeneity of structure, changes in the size and shape of the gland. With Di Giorgi syndrome, thymus aplasia is determined, with myasthenia gravis, thymoma is detected in some patients.
For a more accurate assessment, calculations are carried out using data on the patient’s weight, length, width and thickness of the organ lobes obtained during echography. On their basis, the volume and mass of each lobe are calculated, as well as the total volume and mass of the gland. At the final stage, the thymic index is determined – the mass of the thymus is divided by the body weight of the child, then the resulting figure is multiplied by 100%. The thymic index is compared with the indicators in a special table. Normally, the mass of the thymus gland should be 0.3% of the child’s body weight. With an increase in this indicator, they talk about thymomegaly, with a decrease – about the discrepancy between the size of the gland and the age of the child. With the results of ultrasound of the thymus, you should contact a pediatrician, therapist or immunologist.
A significant increase in the thymic index is a reason for further examination. The child is sent for chest radiography, according to the results, the cardiothymicotoral index and vasocardial index are calculated to determine the degree of thymomegaly. The data of ultrasound and X-ray examination are supplemented with the results of laboratory tests conducted to assess the state of the immune and endocrine system. With thymomegaly of the I degree, special therapeutic measures are not required, with an increase in the organ of the II and III degrees, drug therapy is prescribed.