What is the workup for a 12-year-old girl with abdominal pain and multiple mesenteric lymph nodes around the periumbilical region?

Workup for Multiple Mesenteric Lymph Nodes in a 12-Year-Old Girl with Abdominal Pain

Initial Clinical Assessment

In a 12-year-old girl with periumbilical abdominal pain and multiple mesenteric lymph nodes, the most likely diagnosis is benign reactive lymphadenopathy from a self-limited viral or bacterial infection, but a systematic workup is essential to exclude serious pathology including tuberculosis, inflammatory bowel disease, and lymphoma.

The clinical presentation should focus on:

• Duration and character of pain (acute versus chronic, colicky versus constant) 1
• Associated symptoms: fever, weight loss (>10% in 6 months), night sweats, vomiting, diarrhea, or constipation 2
• Recent infections: respiratory tract infections or gastroenteritis are common triggers 2
• Travel history and TB exposure, particularly in endemic areas 1
• Medication history, especially immunosuppressive agents 3

Imaging Interpretation

Ultrasound findings should be carefully characterized:

• Normal variant: Mesenteric lymph nodes with short-axis diameter ≤8 mm are commonly found in 54% of healthy children and should be considered non-specific 4
• Pathological threshold: Three or more lymph nodes with short-axis diameter ≥10 mm warrant further investigation 2, 4
• Location: Right lower quadrant is the most common site for both benign and pathological nodes 4
• Concerning features: Conglomerates of nodes, nodes >20 mm, or peripheral enhancement with central hypodensity suggest tuberculosis 1

Laboratory Workup

Essential initial laboratory tests include:

• Complete blood count with differential to assess for leukocytosis, leukopenia, anemia, or thrombocytopenia 1, 2
• Inflammatory markers: ESR and CRP to quantify inflammatory burden 2
• Lactate dehydrogenase (LDH) as an early marker of occult lymphoma 3
• Liver and renal function tests 1

Infectious disease screening:

• Tuberculosis testing: PPD or interferon-gamma release assay, particularly if fever, weight loss, or endemic exposure 1
• Stool studies: bacterial culture, ova and parasites (including Giardia lamblia) if diarrhea present 2
• Viral serologies: EBV, CMV, and toxoplasmosis if systemic symptoms or generalized lymphadenopathy 2
• HIV serology in appropriate clinical contexts 1

Advanced Imaging

CT abdomen and pelvis with contrast is indicated when:

• Lymph nodes persist beyond 4-6 weeks despite conservative management 1
• Constitutional symptoms (fever, weight loss, night sweats) are present 1
• Laboratory abnormalities suggest systemic disease (elevated LDH, cytopenias) 3
• Ultrasound shows concerning features (conglomerates, nodes >20 mm) 1, 2

CT findings that require tissue diagnosis:

• Multiple nodes with peripheral enhancement and central hypodensity (tuberculosis pattern) 1
• Nodes >15 mm in short axis 5
• Associated mesenteric masses or soft tissue infiltration 6

Tissue Sampling Indications

Biopsy should be pursued when:

• Persistent unexplained lymphadenopathy beyond 6-8 weeks 5
• Progressive enlargement on serial imaging 6
• Constitutional symptoms with elevated LDH suggesting lymphoma 3
• CT features suggestive of tuberculosis or malignancy 1, 5

Biopsy approach:

• Laparoscopic biopsy is preferred for mesenteric nodes, providing adequate tissue with minimal morbidity (median 2-day hospital stay) 5
• Image-guided percutaneous biopsy may be attempted for larger, accessible nodes 5
• Tissue should be sent for: histopathology, immunohistochemistry (CD20, CD10, CD5, cyclin D1), mycobacterial culture, and molecular studies if lymphoma suspected 1

Management Algorithm

For children with mild symptoms and nodes <10 mm:

• Observation with clinical reassessment in 2-4 weeks 2
• Repeat ultrasound at 4-6 weeks if symptoms persist 2

For children with moderate symptoms or nodes 10-15 mm:

• Complete laboratory workup as outlined above 2
• Consider empiric treatment if specific infection identified (e.g., Giardia) 2
• CT imaging if no improvement after 4-6 weeks 1

For children with severe symptoms, nodes >15 mm, or concerning features:

• Immediate CT imaging 1
• Expedited infectious disease and oncology consultation 3
• Proceed to tissue diagnosis if imaging suggests tuberculosis or malignancy 1, 5

Critical Pitfalls to Avoid

• Do not dismiss persistent lymphadenopathy as "reactive" without adequate follow-up; tuberculosis and lymphoma can present insidiously 1, 6
• Do not rely solely on PPD testing for tuberculosis in immunocompromised patients, as it may be falsely negative 1
• Do not delay biopsy when constitutional symptoms and elevated LDH are present, as this combination suggests lymphoma requiring prompt diagnosis 3
• Do not assume irritable bowel syndrome in children with chronic abdominal pain and mesenteric lymphadenopathy without excluding organic pathology 6