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Pediatr Radiol (2009) 39:616621 DOI 10.1007/s00247-009-1202-0
ORIGINAL ARTICLE
What happens to the thymus in children who have undergone a median sternotomy?
Kelly MacDonald & Stephanie Mackenzie
Received: 27 July 2008 /Revised: 31 December 2008 /Accepted: 14 January 2009 /Published online: 11 March 2009 # Springer-Verlag 2009
AbstractBackground The thymus grows rapidly during fetal life and continues to grow during childhood. When a child undergoes a median sternotomy during cardiac surgery, most of the thymus is removed to gain access to the mediastinum. What happens to the residual thymic tissue in the long term? Objective To test the hypothesis that residual thymic tissue left after sternotomy regenerates into an identifiable thymus and is visible on MRI.
Materials and methods We retrospectively reviewed the cardiac MR images obtained over a 14-month period in all children under the age of 17 years who had undergone a median sternotomy (n=62) to establish the presence/ absence of a thymus. We also reviewed the cardiac MR images obtained over the same time period in children who had never undergone open cardiac surgery (n=37). Results In the sternotomy group, 18 patients (29%) had an identifiable thymus on MR images, compared to 92% (n=34) in the nonsternotomy group. This difference was statistically significant.
Conclusions The majority of children in the study group did not have a visible thymus on MR images, which suggests that in these children any residual thymic tissue left postoperatively does not regenerate.
Keywords Thymus . Sternotomy. MRI . Children
Introduction
The thymus is located in the anterior superior mediastinum. It is the site of T-lymphocyte maturation for the immune system [1]. The thymus grows rapidly throughout fetal life, weighing between 10 g and 15 g at birth [2]. It continues to grow during childhood, reaching its maximum weight and size at puberty (3040 g) [2]. During adulthood, the thymus involutes and, with advancing age, is replaced by adipose tissue. However, although there is a trend for rapid thymic growth prior to adulthood, it is recognized that there is considerable variation between individuals in the size and morphology of the thymus gland in childhood [3, 4], and thus paediatric radiologists learn very early on in their training the importance of considering the thymus gland in the differential diagnosis of anterior...