What are the presentation, diagnostic findings, and treatment options for splenic amoebiasis?

Splenic Amoebiasis: Features and Management

Clinical Presentation

Splenic amoebiasis is an extremely rare complication of Entamoeba histolytica infection that typically presents with fever, abdominal pain, and signs of septic shock, often following amoebic dysentery. 1

Key clinical features include:

• Fever and signs of systemic inflammatory response or septic shock are the predominant presenting symptoms 1
• Clinical splenomegaly is present in only 30% of cases and is not a reliable diagnostic sign 2
• Only 20% of patients give a history of prior dysentery, and only 10% have concurrent diarrhea at presentation 3
• Persistent or recurrent fever despite initial treatment should raise suspicion for splenic involvement 3

Diagnostic Approach

CT scan with intravenous contrast is the gold standard for diagnosis, demonstrating 90-95% sensitivity and specificity for identifying splenic abscesses as contrast-enhancing cystic lesions. 4, 2

Diagnostic workup should include:

• Amoebic serology (indirect haemagglutination) has >90% sensitivity for amoebic abscess 3
• Neutrophil leucocytosis >10×10⁹/L, raised inflammatory markers, and elevated alkaline phosphatase are common laboratory findings 3
• MRI offers equivalent diagnostic accuracy (90-95% sensitivity/specificity) and can differentiate abscesses from bland infarcts 2
• Ultrasound may be used but is less sensitive; abscesses appear as sonolucent lesions 4
• Faecal microscopy is usually negative in patients with amoebic liver abscess and would be similarly unreliable for splenic disease 3

The main differential diagnosis is pyogenic abscess, which is more likely to be multiple and occurs in older patients. 3

Medical Management

Empirical therapy with metronidazole 500 mg three times daily orally for 7-10 days should be initiated immediately upon suspicion, achieving >90% cure rates in amoebic abscesses. 3

Treatment algorithm:

• Tinidazole 2 g daily for 3 days is an alternative that causes less nausea 3, 5
• Broad-spectrum antibiotics (e.g., ceftriaxone plus metronidazole) must be added if pyogenic abscess cannot be excluded until diagnosis is confirmed 3
• Most patients respond within 72-96 hours of initiating therapy 3
• Once treatment with tinidazole or metronidazole is complete, all patients must receive a luminal amoebicide (diloxanide furoate 500 mg three times daily or paromomycin 30 mg/kg/day) to reduce relapse risk, even with negative stool microscopy 3

Important Caveat

Metronidazole neurotoxicity (reversible deafness, tinnitus, ataxia) can occur with high cumulative doses (>21 g), and splenic relapse may occur months after initial treatment 6. Monitor for neurological symptoms and consider tinidazole as first-line to minimize side effects. 5

Interventional Management

Unlike hepatic amoebic abscesses that respond extremely well to antibiotics alone regardless of size, splenic abscesses have higher failure rates with medical therapy alone and more frequently require intervention. 3, 6

Indications for intervention:

• Percutaneous aspiration should be performed if diagnostic uncertainty exists between amoebic and pyogenic abscess 3
• Needle aspiration may be required if symptoms persist after 4 days of medical treatment 3
• Splenectomy is the preferred definitive treatment for splenic abscesses, as percutaneous drainage demonstrates high failure rates (14.3-75%) in this setting 2
• Surgical drainage is indicated for failed medical management or risk of imminent rupture 3

The case literature demonstrates that splenic amoebic abscesses may require two courses of tinidazole, with the second course combined with percutaneous aspiration, to achieve cure. 6 This contrasts sharply with hepatic amoebic abscesses, which rarely require drainage. 3

Post-Splenectomy Considerations

If splenectomy is performed, lifelong vaccination and antibiotic prophylaxis are required to prevent overwhelming post-splenectomy infection (OPSI). 2

• Pneumococcal, meningococcal, and Haemophilus influenzae type B vaccines must be administered 2
• Prophylactic antibiotics should be prescribed indefinitely 2

Key Clinical Pitfalls

• Do not rely on clinical splenomegaly as an indicator of disease severity or presence 2
• Do not assume splenic involvement will behave like hepatic amoebic abscess—splenic disease is more resistant to medical therapy alone 6
• Do not omit luminal amoebicide therapy after completing metronidazole/tinidazole, as this significantly increases relapse risk 3
• Monitor for metronidazole neurotoxicity with prolonged or high-dose therapy 6