Thymic Shadow
    The chest X ray shows a right thymic lobe masquerading as right upper lobe
    opacity.
    The straight inferior border, the sharp and smooth borders, the rim of peripheral
    lucency, and the well condition of the child are all in favor of thymic shadow.

    This child had his thymic shadow confirmed by a lateral film and ultrasonography.
    CXR characteristics of the normal thymus:
    1- No mass effects, no tracheal displacement
    2- Sharp, smooth borders which are slightly convex
    3- Straight inferior border (Sail Sign) usually right sided
    4- Soft and moulds to the ribs, producing scalloped border (Wave Sign)
    5- Notches at its junction with the heart
    6- Homogeneous, soft tissue density
    7- Varies in size- particularly with different phases of respiration and in relation
    to general health
    8- Most often seen in children less than three years of age


    Helen Williams. The normal thymus and how to recognize it. Arch Dis Child
    Educ Pract Ed 2006; 91:ep25-ep28. Read Extract
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