What are the diagnostic and treatment approaches for lymphadenitis?

Diagnostic and Treatment Approaches for Lymphadenitis

The definitive diagnosis of lymphadenitis requires histopathologic examination showing caseating granulomata with or without acid-fast bacilli, and culture of the causative organism from lymph node tissue, typically obtained through excisional biopsy. 1

Clinical Presentation and Evaluation

Cervical Lymphadenitis

• Cervical lymphadenitis typically presents as an insidious, unilateral (95% of cases) and often non-tender mass in the neck region 1
• In children, it most commonly affects those between 1-5 years of age, while in adults, it's important to consider malignancy as a potential cause 1, 2
• Nodes may enlarge rapidly and even rupture, forming sinus tracts with prolonged local drainage 1
• Contrast-enhanced CT typically shows asymmetric adenopathy with ring-enhancing masses that may involve fat and skin but with minimal inflammatory stranding of subcutaneous fat 1

Mesenteric Lymphadenitis

• Often associated with preceding upper respiratory tract infections (22-53% of cases) 3
• Common viral causes include Epstein-Barr virus, Cytomegalovirus, Coxsackievirus, and Rubella 3
• Bacterial causes include Campylobacter jejuni, particularly in Asia 3
• Non-infectious causes include inflammatory bowel disease, adult-onset Still's disease, and malignancies such as lymphoma and leukemia 3

Diagnostic Approach

Initial Evaluation

• All patients with suspected mycobacterial lymphadenitis should undergo tuberculin skin testing 1, 2
• In children with NTM lymphadenitis, tuberculin reactions range from negative to positive, with up to one-third showing reactions of ≥10 mm induration 1
• Complete blood count typically reveals normal or elevated white blood cell count with neutrophil predominance during acute phase 1
• Elevated acute phase reactants such as C-reactive protein and erythrocyte sedimentation rate are common 1

Imaging Studies

• Ultrasonography can help differentiate bacterial lymphadenitis from mycobacterial lymphadenitis 2
• CT scan with contrast is useful for characterizing lymphadenopathy, especially when ultrasonography is inconclusive 3, 2
• In bacterial lymphadenitis, a single node with a hypoechoic core is most common, while in mycobacterial disease, multiple lymph nodes are typically enlarged 1

Definitive Diagnosis

• Fine-needle aspiration (FNA) can provide diagnostic material, though results are variable (50-82% yield) 1
• Excisional biopsy provides the most definitive diagnosis but carries risks, particularly for preauricular nodes where facial nerve injury is possible 1
• PCR has revolutionized the diagnostic approach, enabling identification of previously unrecognized pathogens such as Bartonella henselae and Mycobacterium avium subsp. hominisuis 4
• Histopathology typically shows caseating granulomata with or without acid-fast bacilli 1

Treatment Approaches

Cervical Lymphadenitis

• For mycobacterial non-tuberculous lymphadenitis in children, complete surgical excision without chemotherapy is recommended, with approximately 95% success rate 2
• Incisional biopsy alone or drainage procedures without complete excision should be avoided due to risk of fistula formation and chronic drainage 1, 2
• For tuberculous lymphadenitis, systemic antituberculous medication is the mainstay of treatment 5, 6

Special Considerations

• In HIV-positive patients, lymphadenopathy may represent immune reconstitution inflammatory syndrome after initiating antiretroviral therapy 1, 2
• In adults with persistent lymphadenopathy, particularly those over 40 years, malignancy should be strongly considered 2, 7
• Corticosteroids should be avoided in the evaluation of unexplained lymphadenopathy as they can mask histologic diagnosis of lymphoma or other malignancies 8, 7
• Distinguishing tuberculous from non-tuberculous mycobacterial lymphadenitis is critical, as treatment protocols differ significantly 1, 6

Common Pitfalls and Caveats

• Avoid incisional biopsy or drainage without complete excision in suspected NTM lymphadenitis, as this may lead to fistula formation and chronic drainage 1
• Be cautious when performing excisional biopsy of preauricular lymph nodes due to significant risk of facial nerve injury 1
• Don't administer corticosteroids before establishing a definitive diagnosis, as they can mask signs of lymphoma or other malignancies 8, 7
• Remember that in adults, more than 90% of culture-proven mycobacterial lymphadenitis is due to M. tuberculosis, while in children, approximately 80% is due to non-tuberculous mycobacteria (primarily MAC) 1