Lymph node enlargement (rarely lymphadenomegaly) is often used synonymously with lymphadenopathy, which is not strictly correct.
Lymphadenopathy (or adenopathy) is, if anything, a broader term, referring to any pathology of lymph nodes, not necessarily resulting in increased size; this includes abnormal number of nodes, or derangement of internal architecture (e.g. cystic or necrotic nodes). In addition, increase in size is not always pathologic; some nodes are bigger than others normally (e.g compare jugulodigastric nodes to mesenteric nodes), and reactive nodes are a healthy response and do not imply pathology of the node itself.
There are approximately 600 lymph nodes, of which only some are available to direct palpation. Only some nodes (including neck, axilla and groin) should ever be palpable and these should be soft and non-tender.
There are many (many) causes of lymph node enlargement which include:
- infective (acute suppurative)
- follicular hyperplasia
- paracortical hyperplasia
- sinus histiocytosis
- drug-induced, e.g. cyclosporin, phenytoin, methotrexate
- lipid storage diseases
- IgG4-related sclerosing disease 7
The upper limit in size of a normal node varies with location, and of course the size cut-off used depends on the desired sensitivity and specificity.
Cervical lymph nodes
See the separate article: cervical lymph node metastasis (radiologic criteria).
Mediastinal lymph nodes
In general 10 mm is considered the upper limit for normal nodes (short axis diameter) 3-5. This does not, of course, take into consideration the fact that all nodal metastases must start at microscopic size, and thus using only size criteria will miss micrometastases. In the setting of lung cancer staging a sensitivity of 0.83 and a specificity of 0.82 are quoted for CT 5.
See the separate article: mediastinal lymph node enlargement.
Mesenteric lymph nodes
Mesenteric nodes are increasingly visualized as a result of multidetector volume acquisition and are most easily seen on coronal reformats.
Although 3 mm has previously been used as the upper limit for the short axis diameter of mesenteric lymph nodes, up to 39% of healthy normal patients have larger nodes than this. As such a figure of 5 mm is considered normal 6.
See the separate article: normal mesenteric lymph nodes.
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- 5. Kramer Henk and Harry J.M. Groen. “Current Concepts in the Mediastinal Lymph Node Staging of Nonsmall Cell Lung Cancer.” Annals of Surgery 238, no. 2 (August 2003): 180–188. doi:10.1097/01.SLA.0000081086.37779.1a.
- 6. Lucey BC, Stuhlfaut JW, Soto JA. Mesenteric lymph nodes: detection and significance on MDCT. AJR Am J Roentgenol. 2005;184 (1): 41-4. AJR Am J Roentgenol (full text) - Pubmed citation
- 7. Horger M, Lamprecht HG, Bares R et-al. Systemic IgG4-related sclerosing disease: spectrum of imaging findings and differential diagnosis. AJR Am J Roentgenol. 2012;199 (3): W276-82. doi:10.2214/AJR.11.8321 - Pubmed citation