Incidental 18F-FDG uptake in the colon: value of contrast-enhanced CT correlation with colonoscopic findings

ObjectivesTo evaluate the impact of morphological information derived from contrast-enhanced CT in the characterization of incidental focal colonic uptake in F-18-FDG PET/CT examinations.MethodsA total of 125 patients (female: n = 53, male: n = 72) that underwent colonoscopy secondary to contrast-enhanced, full-dose PET/CT without special bowel preparation were included in this retrospective study. PET/CT examinations were assessed for focal colonic tracer uptake in comparison with the background. Focal tracer uptake was correlated with morphological changes of the colonic wall in the contrast-enhanced CT images. Colonoscopy reports were evaluated for benign, inflammatory, polypoid, precancerous, and cancerous lesions verified by histopathology, serving as a reference standard. Sensitivity, specificity, PPV, NPV, and accuracy for detection of therapeutic relevant findings were calculated for (a) sole focal tracer uptake and (b) focal tracer uptake with correlating CT findings in contrast-enhanced CT.ResultsIn 38.4% (48/125) of the patients, a focal F-18-FDG uptake was observed within 67 lesions. Malignant lesions were endoscopically and histopathologically diagnosed in eleven patients, and nine of these were detected by focal F-18-FDG uptake. A total of 34 lesions with impact on short- or long-term patient management (either being pre- or malignant) were detected. Sensitivity, Specificity, PPV, NPV, and accuracy for sole F-18-FDG uptake for this combined group were 54%, 69%, 29%, 85%, and 65%. Corresponding results for focal F-18-FDG uptake with correlating CT findings were 38%, 90%, 50%, 86%, and 80%. This resulted in a statistically significant difference for diagnostic accuracy (p = 0.0001)ConclusionBy analyzing additional morphological changes in contrast-enhanced CT imaging, the specificity of focal colonic F-18-FDG uptake for precancerous and cancerous lesions can be increased but leads to a considerate loss of sensitivity. Therefore, every focal colonic uptake should be followed up by colonoscopy.