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Mesenteric Lymphadenitis (Adenitis) Imaging

Practice Essentials

Mesenteric lymphadenitis (mesenteric adenitis) is a self-limited inflammatory process that affects the mesenteric lymph nodes in the right lower quadrant. Its clinical presentation mimics that of acute appendicitis.
 Cross-sectional imaging is routinely applied in the examination of patients and may help avoid unnecessary surgery in cases of mesenteric lymphadenitis. Previously, the diagnosis was most frequently made when laparotomy performed to assess presumed appendicitis yielded negative findings.

(See images of mesenteric adenitis below.)

Sonogram of normal mesenteric lymph nodes shows th

Sonogram of normal mesenteric lymph nodes shows that they are ovoid, with a prominent fatty hilum and a short-axis diameter less than 5 mm.

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A thickened ileum and cecum and a normal appendix

A thickened ileum and cecum and a normal appendix are depicted adjacent to an enlarged lymph node in this patient with mesenteric adenitis and terminal ileocolitis.

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Ultrasonography (see the images below) of the right lower quadrant with graded compression has been the mainstay of diagnosis in children.
The American College of Radiology (ACR) recommends this procedure as the most appropriate for pregnant women with fever and leukocytosis and for patients under the age of 14 years with fever, leukocytosis, and possible appendicitis but an atypical presentation.
 

Lymph node clustering in the right lower quadrant.

Lymph node clustering in the right lower quadrant.

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Color sonogram demonstrates nodal hyperemia.

Color sonogram demonstrates nodal hyperemia.

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The ACR notes that abdominal CT (see the images below) with intravenous contrast may be useful in children with negative ultrasound studies and recommends this technique as the most appropriate for adolescents and adults with both the classic and atypical presentation for appendicitis.
 CT is especially useful for evaluation of possible appendicitis in men and in patients in whom visualization of the appendix may be compromised by their body habitus.

MRI without IV contrast may be useful for diagnosis in pregnant women with negative or equivocal ultrasound results.

Although the findings are frequently nonspecific, abdominal radiographs occasionally reveal findings and permit alternative diagnoses (eg, appendicoliths).
 The ACR finds this procedure useful for excluding free air or obstruction.

Abdominal CT scan shows a cluster of enlarged node

Abdominal CT scan shows a cluster of enlarged nodes in the right lower quadrant.

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Mesenteric thickening associated with right lower

Mesenteric thickening associated with right lower quadrant adenopathy.

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In some centers, CT is performed for the evaluation of appendicitis without intravenous and/or oral contrast enhancement. This approach reduces the sensitivity of CT for bowel wall thickening and mesenteric adenopathy, especially in small children with a paucity of intraperitoneal fat.

The normal appendix is sonographically occult in a significant subset of patients. When lymph node enlargement is detected on sonographic examination in these patients, excluding appendicitis as a cause of reactive adenopathy is difficult.

With any imaging modality, the finding of lymph node enlargement as an isolated finding is nonspecific; it can be observed in association with several inflammatory processes. Occasionally, nodes exceeding the normal-size threshold are observed in children who have no demonstrable disease.

In the context of concerns about the radiation dose associated with pediatric CT, tailoring the examination protocol to the patient is prudent to minimize exposure during studies for benign and self-limited conditions such mesenteric lymphadenitis. In this respect, sonography is favored as the initial diagnostic test.

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