Mesenteric lymph nodes in children: what is normal?

Background: Enlarged mesenteric lymph nodes (MLN) are frequently seen in children with abdominal pain and, in the absence of other disorders, have been attributed to primary mesenteric lymphadenitis. Objective: To evaluate the prevalence of enlarged MLN (short axis >= 5 mm) as detected by abdominal CT in children with a low likelihood for mesenteric lymphadenopathy. Materials and methods: During a 14-month period, we identified all non-contrast abdominal CT examinations performed at a tertiary care pediatric hospital for evaluation of suspected or known renal stones. Two radiologists reviewed the examinations and recognized all enlarged MLN, measured the short-axis diameter, and noted the quadrant location. Results: Sixty-one children were identified who met entry criteria; mean age was 10.7 years (range 1.1-17.3 years). Enlarged MLN were found in 33 (54%) of the 61 children; the largest enlarged MLN was most frequently in the right lower quadrant (RLQ) (29 of 33, 88%). Seventeen of the 61 children (28%) had three or more enlarged MLN; all were in the RLQ. The largest short-axis diameter measured was 10 mm. Summary: MLN with a short-axis diameter of > 5-10 mm are commonly found on abdominal CT examination of children with a low likelihood for mesenteric lymphadenopathy and should be considered a non-specific finding. A short-axis diameter of 8 mm might better define the upper limit of normal mesenteric lymph node size in children.