Infected versus sterile abdominal fluid collections in postoperative CT: a scoring system based on clinical and imaging findings

Abstract

Purpose Characterization of intraabdominal fluid collections as postoperative complication is a challenging task. The aim was to develop and validate a new score to differentiate infected from sterile postoperative abdominal fluid collections and to compare it with a published score. Materials and methods From May to November 2015, all patients with postoperative CT and C-reactive protein (CRP) 24 hours before CT-guided drainage were retrospectively included (Group A). HU, gas entrapment and wall enhancement of fluid collections were evaluated in the CT. All parameters were correlated with microbiology. To validate the score and to compare it with a published score, a second patient cohort was retrospectively recruited (Group B; January 2013-April 2015; December 2015-September 2016). Results In Group A (50 patients), univariate analysis confirmed that the four parameters were significantly associated with infected fluid collections. Based on binary logistic regression analysis, a score from 0 to 11 was developed (CRP </≥ 150 mg/l: 0/4 points; HU </≥ 20: 0/2 points; wall enhancement no/yes: 0/2 points; gas entrapment no/yes: 0/3 points). The best cutoff to diagnose infected fluid collections was ≥ 5 points (sensitivity 85%, specificity 79%, PPV 82%, NPV 79%). In Group B (425 patients), this score yielded sensitivity, specificity, PPV and NPV of 93%, 80%, 90% and 86%, respectively. For the published score, values were in the same range (93%, 44%, 77%, 77%). Conclusion The score provides good discrimination between infected and sterile postoperative abdominal fluid collections. It yields comparable accuracy as the published score.

CT Texture analysis and CT scores for characterization of fluid collections

“…Fluid collections are common and can represent ascites, seroma, hematoma, biloma, lymphocele, or abscess depending on the localization and underlying cause [ 1 – 4 ]. The mortality rates associated with infected fluid collections range from 4% in treated cases to more than 80% in untreated cases [ 4 ]. Hence, early and correct diagnosis and treatment are crucial to determine the clinical outcome [ 4 , 5 ].…”

“…The mortality rates associated with infected fluid collections range from 4% in treated cases to more than 80% in untreated cases [ 4 ]. Hence, early and correct diagnosis and treatment are crucial to determine the clinical outcome [ 4 , 5 ]. Many of these patients are suitable for Computed tomography (CT)-guided percutaneous drainage due to advances in CT-guided treatment, whereas surgery is only performed in few selected cases [ 5 ].…”

“…Some imaging features were reported indicative of an infection of a fluid collection, including air entrapment, rim contrast media enhancement and Hounsfield unit (HU) attenuation. However, these imaging features by itself cannot reliably exclude infection due to lack of a sufficient accuracy for correct diagnosis [ 3 , 4 ].…”

“…To this date, only one other study performed a validation analysis for this score and proposed a more accessible combination of imaging findings with only one clinical parameter, namely CRP to correctly diagnose infected fluid collections [ 4 ].…”

How to Handle CT-Guided Abscess Drainages in Microbiological Analyses? Sterile Vials vs. Blood Culture Bottles for Transport and Processing

“…In these studies, positivity rates ranged between 24 and 26% [ 20 , 21 , 32 ]. Studies on microbiologic diagnostics of CT-guided drainage material from abdominal abscesses led to a comparable positive detection rate ranging from 60–78%, without specifying their culture methods [ 10 , 33 , 34 ]. To our best knowledge, only one study has evaluated the blood culture method for microbiological diagnostics of brain abscesses, but not in comparison with conventional culture methods [ 35 ].…”