Application of Roentgen Ray in Diagnosis of Conditions of the Thymus Gland in Children

Abstract

FOR practical purposes, the conditions of the thymus gland in children which require consideration are: (1) Enlargement or hyperplasia. It has been felt for many years that the thymus, resting in close apposition to the trachea and great vessels and nerves at the point where they come through the rigid bony superior thoracic inlet, may, by its enlargement, so compress these important structures as to produce obstructive symptoms such as dyspnea, stridor, coughing or choking, and cyanosis, at times to the point where asphyxiation and death may result. (2) The condition of status thymico-lymphaticus, described as a combination of constitutional hereditary anomalies which includes preservation or hyperplasia of the thymus, hyperplasia of the lymphoid tissue of the intestines, spleen and elsewhere, with hypoplasia of the aorta and cardiovascular system and of the adrenals. Such individuals may suddenly die from the most trivial causes, and it has been thought that the finding of a large thymus may be a direct indication that this diathesis exists. Others believe that this condition may exist without obvious enlargement of the thymus. Roentgen Diagnosis The application of the roentgen ray may be of diagnostic aid in these conditions in the following ways: (1) in showing enlargement of the gland; in detecting pressure phenomena, particularly of the trachea; the possible diagnostic value of a therapeutic test with roentgen rays. Normal Roentgen Appearance.—The normal infant's chest, so well described by Wasson (1) in his observations on the anatomy of the thymus gland, shows in the anteroposterior views (Fig. 1) two auricles and the great vessels forming the base of the heart shadow, the superior vena cava at the right and the pulmonary artery on the left. The aorta lies in the midline; only in later life does it project to form the aortic arch. These structures form a triangular shadow which narrows as it passes upward toward the first rib. At its narrowest point it is less than the diameter of the spinal column. The trachea is in the midline behind the aorta, bifurcating at about the third thoracic vertebra; the esophagus lies behind the trachea and is not seen. The thymus is included in the superior mediastinal shadow, its base overlapping the base of the heart. It is usually widest at the third interspace. In the recumbent postero-anterior position at full inspiration, the normal mediastinal shadow at the second interspace is about one and one-half times the width of the body of a dorsal vertebra. The lateral view should show the pharynx, posterior border of the tongue, epiglottis, vestibule of the larynx, retropharyngeal space, and the trachea. There may be slight buckling or narrowing of the trachea, but no definite constriction or collapse.