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

Purpose To compare the diagnostic performance of 18F-fluorodeoxyglucose-PET/MRI and MRI in the diagnosis of pelvic recurrence of rectal cancer. Methods All PET/MRIs of patients in the follow-up of rectal cancer performed between 2011 and 2018 at our institution were retrospectively reviewed. Recurrence was confirmed/excluded either by histopathology or imaging follow-up (> 4 months). Four groups of readers (groups 1/2: one radiologist each, groups 3/4: one radiologist/one nuclear medicine physician) independently interpreted MRI and PET/MRI. The likelihood of recurrence was scored on a 5-point-scale. Inter-reader agreement, sensitivity, specificity, PPV/NPV and accuracy were assessed. ROC curve analyses were performed. Results Fourty-one PET/MRIs of 40 patients (mean 61 years ± 10.9; 11 women, 29 men) were included. Sensitivity of PET/MRI in detecting recurrence was 94%, specificity 88%, PPV/NPV 97% and 78%, accuracy 93%. Sensitivity of MRI was 88%, specificity 75%, PPV/NPV 94% and 60%, accuracy 85%. ROC curve analyses showed an AUC of 0.97 for PET/MRI and 0.92 for MRI, but the difference was not statistically significant (p = 0.116). On MRI more cases were scored as equivocal (12% versus 5%). Inter-reader agreement was substantial for PET/MRI and MRI (0.723 and 0.656, respectively). Conclusion 18F-FDG-PET/MRI and MRI are accurate in the diagnosis of locally recurrent rectal cancer. Sensitivity, specificity, PPV, NPV and accuracy are comparable for both modalities, but PET/MRI increases readers’ confidence levels and reduces the number of equivocal cases. Graphic abstract