Laboratory Studies
The following laboratory studies may aid in the evaluation of patients with suspected mesenteric lymphadenitis:
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Complete blood cell (CBC) count: Leucocytosis is present, with white blood cells (WBCs) exceeding 10,000/µL occurs in at least 50% of cases.
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Chemistry panel: Findings are generally within reference ranges, except in patients with severe nausea and vomiting who may present with metabolic alkalosis and azotemia.
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Serology can be supportive in diagnosis of etiologic agents such as Y enterocolitica. Serologic tests tend to be delayed, and several antigens may have to be tested.
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Urinalysis may be useful to perform when the diagnosis is unclear and to exclude urinary tract infection.
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In patients who present with diarrheal symptoms, stool cultures should be performed.
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Blood culture: This is performed prior to prescribing antibiotics and in patients who have features of septicemia. Isolation of the organism from blood, lymph nodes, or other body fluids will help define appropriate therapy and guide further evaluation.
Specific cytokine levels in conjunction with WBC counts may help to differentiate between pediatric acute mesenteric lymphadenitis and acute appendicitis. In a prospective study (2010-2013) of 31 children with acute appendicitis, 26 with acute mesenteric lymphadenitis, and 17 with elective noninflammatory surgical disease (control group), Zviedre et al found that a 1-hour preoperative interleukin (IL)-6 cut-off value of 4.3 pg/mL (67.7% sensitivity; 76.9% specificity) combined with a WBC count cut-off value of 10.7 × 103/μL (71.0% sensitivity; 46.2% specificity) was more sensitive for acute appendicitis. [8]
Other laboratory studies
In patients subjected to laparotomy, lymph node specimens may show evidence of inflammation or suppuration, and culture may yield a causative organism.
In the presence of mesenteric lymphadenitis with obvious terminal ileal thickening (eg, Crohn disease, infectious ileitis) (ie, secondary mesenteric lymphadenitis), obtain/perform endoscopic biopsies, stool cultures, or small-bowel barium studies to determine the underlying cause of the adenitis, particularly in cases refractory to conservative therapy. [1]
Imaging Studies
Computed tomography scanning
Contrast computed tomography (CT) scanning demonstrates enlarged mesenteric lymph nodes, with or without associated ileal or ileocecal wall thickening, and a normal appearing appendix. In mesenteric adenitis, lymph nodes tend to be larger, greater in number, and more widely distributed than in appendicitis. Rao et al specified the criterion of three or more nodes with a short-axis diameter of at least five clustered in the right lower quadrant. CT scanning is also important to exclude other differential diagnoses, especially acute appendicitis.
Magnetic resonance imaging
Contrast-enhanced magnetic resonance imaging (MRI) can differentiate between acute appendicitis and other causes of pediatric abdominal pain, with good visualization of the appendix. [9] More information is needed whether contrast enhancement with MRI has an advantage over non-enhanced MRI in this setting.
Ultrasonography
Abdominal ultrasonographic scanning with Doppler scanning is a useful adjunct for excluding other differential diagnoses. [2, 4, 10] For instance, ultrasonographic demonstration of mural thickening of the terminal ileum plus mesenteric thickening is indicative of regional enteritis. Focal abdominal tenderness in response to transducer pressure is common. Ultrasonography is often the preferred initial diagnostic procedure, especially in children with uncomplicated abdominal pain.
A study by Ja Lim et al supported the use of ultrasonography in the diagnosis of mesenteric lymphadenitis. The retrospective study involved 100 children with clinically suspected intussusception, with abdominal ultrasonography instead demonstrating the presence of mesenteric lymphadenitis in 13 of these patients. Other conditions identified in the study included ileocolitis, terminal ileitis, choledochal cyst, accessory spleen torsion, small bowel ileus, midgut volvulus with bowel ischemia, and hydronephrosis, as well as intussusception (in 37 patients). [11]
Sheridan et al demonstrated the potential utility of ultrasonography to stratify patients with acute appendix into different treatment strategies. [12] They found that (1) a fluid-filled appendix always correlated with a suppurative or mixed pathologic appearance that likely warranted operative intervention, and (2) a lymphoid-predominant pathologic appearance occurred only in cases where appendiceal wall thickening alone was seen on ultrasonography. [12]
A study by Zu et al evaluated superb microvascular imaging (SMI) in the diagnosis of mesenteric lymphadenitis and concluded that SMI was superior to color Doppler flow imaging in evaluating the microvasculature in lymphadenopathy in mesenteric lymphadenitis. The retrospective study compared lymph node size determined using grayscale ultrasonography and lymph node vascularity using color Doppler flow imaging (CDFI) and SMI in 27 children with mesenteric lymphadenitis and 30 healthy children. SMI identified 92.6% of abnormal mesenteric lymph nodes while CDFI detected 85.2%. Ultrasonography combined with SMI had the highest sensitivity (81.5%), and specificity (78.9%) compared with ultrasonography alone (sensitivity, 63.0%; specificity, 64.9%). [13]
