Rifaximin suppresses background intestinal 18F-FDG uptake on PET/CT scans

Nucl Med Commun. 2014 Oct;35(10):1026-31. doi: 10.1097/MNM.0000000000000170.


Background: Identification of cancer or inflammatory bowel disease in the intestinal tract by PET/computed tomography (CT) imaging can be hampered by physiological uptake of F-fluorodeoxyglucose (F-FDG) in the normal colon. Previous work has localized this F-FDG uptake to the intestinal lumen, predominantly occupied by bacteria. We sought to determine whether pretreatment with an antibiotic could reduce F-FDG uptake in the healthy colon.

Patients and methods: Thirty patients undergoing restaging PET/CT for nongastrointestinal lymphoma were randomly selected to receive rifaximin 550 mg twice daily for 2 days before their scan (post-rifaximin). Their PET/CT images were compared with those from their prior study (pre-rifaximin). Cecal maximum standard uptake value (SUVmax) and overall colonic F-FDG uptake were compared between scans. All PET/CT images were blindly scored by a radiologist. The same comparison of sequential scans was also undertaken in 30 patients who did not receive antibiotics.

Results: Thirty post-rifaximin scans were compared with 30 pre-rifaximin scans in the same patients. SUVmax in the cecum was significantly lower in the patient's post-rifaximin scans than in their pre-rifaximin scans (P=0.002). The percentage of scans with greater than grade 1 colonic F-FDG uptake was significantly lower in the post-rifaximin scans than in the pre-rifaximin scans (P<0.05). In contrast, there was no significant difference in the paired sequential scans from control patients, nor a reduction in the percentage of scans with greater than grade 1 colonic F-FDG uptake.

Conclusion: This pilot study shows that treatment with rifaximin for 2 days before PET/CT scanning can significantly reduce physiological F-FDG uptake in the normal colonic lumen.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Anti-Bacterial Agents / pharmacology*
  • Cecum / diagnostic imaging
  • Cecum / metabolism
  • Cohort Studies
  • Colon / diagnostic imaging
  • Colon / metabolism
  • Drug Interactions
  • Female
  • Fluorodeoxyglucose F18 / pharmacokinetics*
  • Humans
  • Image Processing, Computer-Assisted
  • Intestinal Mucosa / metabolism*
  • Intestines / diagnostic imaging*
  • Male
  • Middle Aged
  • Positron-Emission Tomography
  • Prospective Studies
  • Radiopharmaceuticals / pharmacokinetics*
  • Rifamycins / pharmacology*
  • Rifaximin


  • Anti-Bacterial Agents
  • Radiopharmaceuticals
  • Rifamycins
  • Fluorodeoxyglucose F18
  • Rifaximin