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The Influence of Medical Comorbidity On the Development and Severity of Biliary Infections: a Multivariate Analysis Utilizing the Charlson Comorbidity Index
Lygia Stewart*1,2, J. Mcleod Griffiss3, Gary a. Jarvis3, Lawrence W. Way1
1Surgery, UCSF, San Francisco, CA; 2Surgery, SF VAMC, San Francisco, CA; 3Microbiology, Lab Medicine, SF VAMC, San Francisco, CA

Objective: Clinical factors associated with biliary infections include advanced age, male sex, pigment stones, and choledocholithiasis. These factors, and the presence of bacterial-laden gallstones, determine the severity of biliary infections. The influence of comorbidity on the development and severity of biliary infections, however, is not known. We examined this using clnical parameters.
Methods: 337 patients with gallstone disease were studied. Gallstones, bile, and blood (as applicable) were cultured. Gallstones were grouped by appearance (predominently cholesterol stones, pigment stones). Medical comorbidity was quantified using the Charlson Comorbidity Index (CCI). Severity of the acute illness was classified as: none (no infectious manifestations), SIRS (fever, leukocytosis), severe (abscess, cholangitis, empyema), or MODS (bacteremia, hypotension, organ failure). The association between CCI and biliary infections was studied using univariate analysis; and multivatiate analysis utilizing clinical factors associated with bacterial infections (age, male sex, choledocholithiasis, pigment stones).
Results: Bacteria were present in gallstones in 46%, bile in 38%, and blood in 8% of cases. CCI>3 independently correlated with pigment stone formation(table). Cases with CCI>3 more often harbored bacteria in gallstones, bile, and blood; but only bacteremia correlated with CCI>3 on multivatiate analysis(table). With exclusion of stone type, CCI>3 also correlated with gallstone bacteria and bactibilia on multivariate analysis. CCI>3 correlated with the development of MODS(table). Subgroup analysis showed no association between CCI and illness severity in cases with gallstones confined to the gallbladder. But, among cases with bacterial-laden CBD stones, CCI>3 correlated with MODS manifestations(table).
Conclusions: This is the first study to show the importance of comorbidity to the development of biliary infections, as well as bacterial access to the systemic circulation. It also correlated with pigment stone formation (which usually harbor bacteria), a finding not predicted by other studies on comorbidity. But most importantly it was an independent factor for the development of the most serious biliary infections.
Asssociation Between CCI and Biliary Infections

CCI<3 CCI>3 Univariate P Value Multivariate P Value
Pigment Stones 46% 67% < 0.0001 0.008
Gallstone Bacteria 39% 58% 0.001 0.159
Bactibilia 26% 53% < 0.0001 0.059
Bacteremia 5% 15% 0.001 0.024
Illness Severity (All) 18% Sev/MODS 31% Sev/MODS 0.002 0.316
MODS (All) 9% 22% 0.001 0.039
MODS (w/CBD stones) 18% 46% 0.003 0.026

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