Unexpected FDG-PET uptake in the gastrointestinal tract: Endoscopic and histopathological correlations

Abstract

Unexpected FDG uptake in the GIT is commonly encountered and may contain significant findings. Endoscopy evaluation is justified in order to detect these additional findings.

Clinical significance of incidental 18FDG PET uptake in the gastrointestinal tract: a retrospective cohort study

“…Published cases of unexpected upper gastrointestinal PET uptake have been associated with endoscopic findings of Barrett's oesophagus, Helicobacter pylori ‐associated gastritis, Candida oesophagitis and gastric adenocarcinoma 13–17 . Previous retrospective studies evaluating incidental PET uptake in the upper GIT have found new malignancies in up to 25% of cases; however, these have been over a small time period of 2 years 18,19 . One of these studies only had data from endoscopic assessment available in 70% of the eligible patients 19…”

“…It permits visualisation and quantification of neoplastic disease, with information about molecular features, particularly metabolic activity and receptor expression. 1,2 The most commonly used tracer is 18 F (fluorine)-labelled glucose analogue fluorodeoxyglucose (FDG), which is taken up by cells with high metabolic activity via the cell membrane glucose transporters. This allows three-dimensional measurements of the distribution of positron-emitting labelled radiotracer and non-invasive quantitative assessment of the biochemical and functional process.…”

“…This allows three-dimensional measurements of the distribution of positron-emitting labelled radiotracer and non-invasive quantitative assessment of the biochemical and functional process. 3 Incidental 18 FDG uptake across a wide range of different organs is not uncommon when evaluating a whole-body PET scan. The gastrointestinal tract (GIT) and thyroid are the most frequent sites of focal incidental uptake.…”

“…4 Early endoscopic evaluation of incidental positive PET scan findings is essential to exclude any concurrent neoplastic pathology, which may require urgent treatment. 18 FDG-PET has been shown to be highly sensitive for colorectal neoplastic disease; however, its specificity is lowered due to wide variation in physiologic 18 FDG avidity of the GIT. This has been commonly attributed to localised mucosal, muscular, bacterial or lymphocytic uptake.…”

“…7 Past research found that incidental uptake with a focal or diffuse pattern can be observed in the colorectum in 2.4% of all whole-body PET scans. 6,9 It has been suggested that the presence of focal 18 FDG uptake on PET-CT is more likely to correlate with pathological findings such as inflammatory lesions or polyps, while a diffuse pattern of 18 FDG uptake correlates with the physiological activity of bowel wall smooth muscles. 10,11 Several small cohort studies have reported that 10-25% of patients undergoing colonoscopic evaluation for incidental focal 18 FDG uptake have a malignant lesion.…”