What are the causes of splenic abscesses?

Causes of Splenic Abscess

Splenic abscesses arise primarily from hematogenous spread of infection (most common), contiguous spread from adjacent infections, or secondary infection of splenic infarcts, with infective endocarditis being the leading identifiable source. 1, 2

Primary Mechanisms of Abscess Formation

Hematogenous Spread (Most Common Route)

• Infective endocarditis is the most frequently identified source, with splenic involvement occurring in 40% of left-sided endocarditis cases, though only 5% progress to abscess formation 3
• Viridans streptococci and Staphylococcus aureus each account for 40% of splenic abscess cases in endocarditis, with enterococci responsible for 15% 1
• Distant sites of infection can seed the spleen through bacteremia, particularly in immunocompromised hosts 2

Secondary Infection of Splenic Infarcts

• Bland splenic infarcts can become secondarily infected, progressing to abscess formation 2
• This progression is indicated by persistent fever, recurrent bacteremia, or enlargement of splenic defects on serial imaging 4, 3

Contiguous Spread

• Direct extension from adjacent abdominal infections can cause splenic abscess 2, 5

Trauma-Related

• Splenic trauma with subsequent infection represents another mechanism, though less common 2, 5

Major Predisposing Conditions

Immunocompromised States (Most Important Risk Factor)

• Immunosuppression is present in 72% of splenic abscess cases, making it the most significant risk factor 6
• Leukemia is the most common associated condition in reported series 6
• HIV/AIDS and other immunodeficiency states substantially increase risk 5

Underlying Hematologic Malignancies

• Hematologic cancers, particularly leukemia, are strongly associated with splenic abscess development 6

Infective Endocarditis

• As noted above, this is the leading identifiable infectious source for hematogenous seeding 1, 3

Causative Organisms

Bacterial Pathogens (Most Common)

• Enterobacteriaceae, gram-positive cocci, and anaerobes are the most frequently isolated organisms 7
• Specific organisms identified include E. coli, Citrobacter freundii, Streptococcus viridans, and anaerobes 5
• Blood cultures are positive in only 24-80% of cases, while abscess cultures after drainage yield organisms in 50-80% 7

Fungal Pathogens

• Candida albicans is documented in immunocompromised patients 5

Unusual Organisms in Immunocompetent Hosts

• Tuberculosis, Salmonella, and even Plasmodium vivax have been reported as rare causes in immunocompetent adults 8

Clinical Pitfalls to Recognize

• Current understanding of splenic abscess etiology remains limited, and additional risk factors beyond those traditionally recognized may exist 2
• The nonspecific clinical picture makes diagnosis challenging, requiring high clinical suspicion in febrile patients with appropriate risk factors 6
• Clinical splenomegaly is present in only 30% of cases and should not be relied upon as a diagnostic indicator 3