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Abstract

Introduction: Although post-splenectomy is a well-known risk factor for the development of overwhelming sepsis especially by encapsulated bacterial organisms such as Streptococcus pneuoniae, the relationship between the size of the spleen and severity of pneumococcal sepsis has not been fully clarified. Only a few case reports have indicated an association between anatomical hyposplenia and overwhelming pneumococcal sepsis. Hypothesis: The small-sized spleen observed in a computed tomography (CT) scan is an independent predictor of increasing severity in adult pneumococcal sepsis. Methods: Adult patients with blood-culture-positive pneumococcal sepsis admitted to our hospital from May 1, 2005 to July 31, 2011 were retrospectively analized. The volume of the spleen was estimated by CT using ‘triangular pyramid model’. We defined life-threatening pneumococcal sepsis as having either hypotension (systolic blood pressure less than 90mmHg) or fulminant purpura on arrival, and also defined hyposplenia as having the estimated spleen size less than 10 cm3. Results: Forty-one patients were enrolled in the study. Six patients were excluded because CT examination was not perfomed and 1 patient was excluded because she was splenectomized. The estimated spleen volume by CT was not significantly different between the life-threatening group (n=10) and the non-life-threatening group (n=24) (9.7 vs. 31.4 cm3, p=0.1 by Mann-whitney U-test). Five hyposplenic patients among which 4 died during hospitalization were found in the life-threatening-group, while only 1 patient in the non-life-threatening group was found hyposplenic and discharged alive (p=0.005 by Fisher’s test). Multiple logistic regression analysis demonstrated that hyposplenia was an independent predictor of developing life-threatening pneumococcal sepsis (OR, 23.0; 95%CI, 2.2-242.3; p=0.009). Conclusions: Anatomically hyposplenic patients assessed by CT may have an increased risk of developing overwhelming sepsis and mortality in pneumococcal sepsis in adults.