Normal mesenteric lymph nodes

In the pre-multidetector CT era, mesenteric lymph nodes were only really appreciated when enlarged. Following the advent of routine volume acquisition CT (and especially coronal reformats) they are commonly seen in normal individuals, which has raised the obvious question of what counts as mesenteric nodal enlargement.

As with all such questions (e.g size of common bile duct, size of pancreatic duct etc.), it is really a statistical question determined by:

  • size distribution of normal nodes
  • size distribution of pathological nodes
  • desired sensitivity and specificity

As there is clearly a degree of overlap between the size of normal and abnormal nodes the literature is replete with various figures. Various upper limits of normal for short axis diameter include 1:  

  • 3 mm: too conservative, with 39% of normal individuals having nodes larger than this
  • 4-5 mm: probably a reasonable compromise 1,2
  • 9-11 mm: may miss many abnormal nodes

The other factor to consider is the number of nodes, which may be elevated in patients with some hematological disorders without clearly being abnormal in size ref

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rID: 13639
Section: Approach
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