Tampon

A tampon is readily identified on CT images by its well-defined tubular appearance, its anatomic location in the pelvis, and its air-equivalent density.

Tampons are nearly always non-avid on PET images. 

Occasionally, tampons can be intensely FDG-avid.  This activity has been presumed inflammatory, related to menses. More recently, however, it has been demonstrated that this tampon uptake is more likely related to urinary contamination.

While such activity is normal, it is worth mentioning in the body of the report, so that clinicians do not call you about this rather impressive looking finding.