title: Clinical significance of incidental [18 F]FDG uptake in the gastrointestinal tract on PET/CT imaging: a retrospective cohort study.
abstract: BACKGROUND
  The frequency and clinically important characteristics of incidental (18)F-fluorodeoxyglucose ([18 F]FDG) positron emission tomography (PET) uptake in the gastrointestinal tract (GIT) on PET/CT imaging in adults remain elusive.
  
  
  METHODS
  All PET/CT reports from 1/1/2000 to 12/31/2009 at a single tertiary referral center were reviewed; clinical information was obtained from cases with incidental (18)F-FDG uptake in the GIT, with follow-up through October, 2012.
  
  
  RESULTS
  Of the 41,538 PET/CT scans performed during the study period, 303 (0.7 %) had incidental GIT uptake. The most common indication for the PET/CT order was cancer staging (226 cases, 75 %), with 74 % for solid and 26 % for hematologic malignancies. Of those with solid malignancy, only 51 (17 %) had known metastatic disease. The most common site of GIT uptake was the colon, and of the 240 cases with colonic uptake, the most common areas of uptake were cecum (n = 65), sigmoid (n = 60), and ascending colon (n = 50). Investigations were pursued for the GIT uptake in 147 cases (49 %), whereas 51 % did not undergo additional studies, largely due to advanced disease. There were 73 premalignant colonic lesions diagnosed in 56 cases (tubular adenoma, n = 36; tubulovillous adenoma with low grade dysplasia, n = 27; sessile serrated adenoma, n = 4; tubulovillous adenoma with high grade dysplasia, n = 3; villous adenoma, n = 3), and 20 cases with newly diagnosed primary colon cancer. All 20 (100 %) patients with malignant colonic lesions had a focal pattern of [18 F]FDG uptake. Among cases with a known pattern of [18 F]FDG uptake, 98 % of those with premalignant lesions had focal [18 F]FDG uptake. Eighteen (90 %) of the cases with newly diagnosed colon cancer were not known to have metastatic disease of their primary tumor. Areas of incidental uptake in the ascending colon had the greatest chance (42 %) of being malignant and premalignant lesions than in any other area.
  
  
  CONCLUSIONS
  Focality of uptake is highly sensitive for malignant and premalignant lesions of the GIT. In patients without metastatic disease, incidental focal [18]FDG uptake in the GIT on PET/CT imaging warrants further evaluation.
authors.affiliation: Division of Gastroenterology, Department of Internal Medicine, Mount Sinai Medical Center, New York, NY, USA.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Shmidt
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: Vandana
authors.initials: V
authors.lastname: Nehra
authors.affiliation: Division of Nuclear Medicine, Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA.
authors.forename: Val
authors.initials: V
authors.lastname: Lowe
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA. oxentenko.amy@mayo.edu.
authors.forename: Amy S
authors.initials: AS
authors.lastname: Oxentenko
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003106:Colon / Q000000981:diagnostic imaging / Q000378:metabolism; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D005767:Gastrointestinal Diseases / Q000000981:diagnostic imaging / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000000981:diagnostic imaging* / Q000378:metabolism; D006801:Humans; D033162:Incidental Findings; D008297:Male; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography / Q000379:methods / Q000706:statistics & numerical data*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics*; D012189:Retrospective Studies
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: 18 F-fluorodeoxyglucose ([18 F]FDG); Incidental colorectal lesions; Positron emission tomography/computed; Tomography (PET-CT)