Normal lymph node size in the mediastinum: a retrospective study in two patient groups.

The size and number of normal mediastinal lymph nodes seen on computed tomography were studied retrospectively in 110 patients from the Royal Marsden Hospital, Sutton, and St Bartholomew's Hospital, London. The mediastinum was divided into four areas. Lymph nodes were seen in 81% of patients. The number of patients with nodes in a specific area varied from 28% in the right superior mediastinum to 46% in the pretracheal retrocaval space. Seventeen per cent of the areas studied contained one node, 11% contained two or three nodes and 4% had three nodes. Fewer nodes were seen in patients with sparse mediastinal fat. Sixty-seven per cent of patients had nodes measuring 5 mm or less in maximum transverse diameter and 21% of patients had one or more nodes of 6-10 mm. Only a single calcified node measured more than 10 mm. We conclude that the majority of nodes are 5 mm or less in diameter and that almost all normal nodes measure 10 mm or less.