Table 1.

Differences between amoebic and pyogenic abscess

	Amoebic abscess	Pyogenic abscess
Pathogen	Entamoeba histolytica	Klebsiella pneumoniae, Streptococcus milleri, Escheria coli, Burkholderia pseudomallei, Staphylococcus aureus, Polymicrobial including anaerobes
Distribution	Globally, higher rates in LMICs, typically males 30–50 years	Globally, older patients
Acquisition	Poor sanitation, contaminated drinking water	Biliary source, e.g. impacted gall stone Systemic infection
Pathogenesis	Inflammation—abundant neutrophils	Necrosis—absence of neutrophils
Imaging	Usually single (can be multiple) Typically in right lobe (can be in left lobe) Cold appearance on sulfur colloid scan	Either single or multiple Any lobe can be involved Hot appearance on sulfur colloid scan
Fine needle aspirate	Macroscopic—thick, chocolate brown, odourless, ‘anchovy paste’ Microscopy for trophozoites—insensitive (25%) Antigen testing—sensitive and specific, generally not available in LMICs PCR—sensitive and specific, generally not available in LMICs	Macroscopic—purulent, may be foul smelling Culture—limited availability in LMICs
Other diagnostic modalities	Serology—useful in returned travelers, limited role in residents of high endemicity Antigen testing of serum—sensitive and specific, generally not available in LMICs	Blood cultures—sensitivity 50%, limited availability in LMICs, in LMICs patients often pre-treated with antimicrobials prior to specimen collection.
Treatment	Medical therapy with metronidazole usually sufficient. (May require drainage in co-infection or impending rupture.)	Percutaneous drainage along with antibiotics is mainstay of therapy. Antibiotic treatment in small responsive abscesses.