Role of F-18 FDG PET/CT in evaluation of gall bladder lesions suspicious of malignancy

Objectives This study was carried out to evaluate the role of F-18 FDG PET/CT in evaluation of gall bladder lesions suspicious of malignancy.

Methods 24 patients with a suspicion of gall bladder carcinoma on the basis of symptomatology or on conventional imaging modalities were included in the study. Interpretation criteria included SUV greater than SUV of mediastinal blood pool was considered suggestive of malignancy. Correlation with inflammatory markers(CRP) whenever required and available.

Results Out of 24, 21 patients had increased FDG uptake in the gall bladder. SUV values ranged from 5 -14.9 with a mean of 8.2.3 patients did not have increased FDG uptake in the gall bladder. Final diagnosis of gall bladder carcinoma was made in 20. Other 4 had a diagnosis of cholecystitis. FDG PET/CT was true positive in 18/20 patients and false negative in two patients. 4 false positive cases included one case of xanthogranulomatous cholecystitis and 3 as acute or acute on chronic cholecystitis. Out of 3 patients without increased FDG uptake one was true negative which was later diagnosed as chronic cholecystitis and two patients were false negative on FDG PET/CT were confirmed as mucinous adenocarcinoma. So FDG PET/CT had a sensitivity of 90%, PPV of 81% and a specificity of 25% and NPV of 33% in predicting the malignant nature of gall bladder lesions. Of the four false positive cases on FDG PET/CT three patients had elevated CRP when taken into consideration specificity increased to 50%.

Conclusions FDG PET /CT is a very sensitive investigation in predicting the malignant nature of gall bladder lesions. Correlation with inflammatory markers would be useful to further increase the specificity