title: PET/CT detection of unexpected gastrointestinal foci of 18F-FDG uptake: incidence, localization patterns, and clinical significance.
abstract: Precise PET/CT localization of focal (18)F-FDG uptake in the gastrointestinal tract (GIT) may exclude malignancy in sites of physiologic activity but may also induce false-negative reports for malignant or premalignant lesions. The purpose of the present study was to retrospectively evaluate the nature and significance of unexpected focal (18)F-FDG uptake localized by PET/CT within the GIT.
  
  
  METHODS
  The files of 4,390 patients referred for (18)F-FDG PET/CT were retrospectively reviewed. The incidence of studies showing unexpected focal uptake of (18)F-FDG localized by PET/CT to the GIT was determined. The position of these foci along the GIT and their intensity were recorded. The etiology of the findings was confirmed histologically or by long-term follow-up.
  
  
  RESULTS
  Unexpected focal (18)F-FDG uptake in the GIT was found in 58 patients (1.3%). Follow-up data were available for 34 of these patients, including 4 with sites in the stomach, 2 in the small bowel, and 28 in the colon. GIT-related disease was confirmed in 24 patients (71%). There were 11 malignant tumors, 9 premalignant lesions, and 4 benign processes including 2 benign polyps, 1 case of active gastritis, and 1 abscess of the sigmoid. Ten patients (29%) had no further evidence of GIT abnormality, and the suggestive sites were considered to be physiologic uptake. Maximal standardized uptake value was 17.3 +/- 10.2 in malignant lesions, 14.0 +/- 10.5 in premalignant lesions, 18.0 +/- 12.1 in benign lesions, and 11.1 +/- 7.4 in foci of physiologic (18)F-FDG uptake in the GIT, with no statistically significant difference among the 4 subgroups.
  
  
  CONCLUSIONS
  Incidental focal (18)F-FDG uptake localized by PET/CT within the GIT is of clinical significance in most patients. These findings should be followed up with appropriate invasive procedures guided by hybrid imaging results.
authors.affiliation: Department of Nuclear Medicine, Rambam Medical Center, Haifa 35254, Israel. o_israel@rambam.health.gov.il
authors.forename: Ora
authors.initials: O
authors.lastname: Israel
authors.forename: Nikolay
authors.initials: N
authors.lastname: Yefremov
authors.forename: Rachel
authors.initials: R
authors.lastname: Bar-Shalom
authors.forename: Olga
authors.initials: O
authors.lastname: Kagana
authors.forename: Alex
authors.initials: A
authors.lastname: Frenkel
authors.forename: Zohar
authors.initials: Z
authors.lastname: Keidar
authors.forename: Doron
authors.initials: D
authors.lastname: Fischer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D005770:Gastrointestinal Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism*; D006801:Humans; D015994:Incidence; D033162:Incidental Findings; D007557:Israel / Q000453:epidemiology; D008875:Middle Aged; D049268:Positron-Emission Tomography / Q000706:statistics & numerical data*; D011230:Precancerous Conditions / Q000175:diagnosis / Q000453:epidemiology / Q000378:metabolism; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013382:Subtraction Technique / Q000706:statistics & numerical data*; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18