Visualization of an Insect Bite on a Bone Scan

From the Department of Nuclear Medicine, Saint-John’s General Hospital, Brugge, Belgium.
Frank De Geeter, MD, PhD.


A 48-year-old woman underwent bone scintigraphy for the assessment of possible trochanteric bursitis on the left side. Whole-body images taken 3 hours after injection of 20 mCi (740 MBq) of Tc-99m-oxidronate are unremarkable except for a rounded area of slightly increased activity at the back of the right thigh (arrow). The gray scale has been adjusted to enhance this area.

 lateral spot view locates the increased activity superficially to the back of the right thigh. On physical examination, a large (10-cm) circular zone of redness was present in this area. The patient remembered having been bitten or stung by an insect, probably a horsefly, while sitting
in her backyard on the evening before the bone scan.
Many insect bites, including those of horseflies (also known as tabanids), are known to cause inflammatory skin lesions, not so much as a result of the physical injury of the bite, but mainly as a result of irritant substances concentrated in insect saliva such as anticoagulants, enzymes, agglutinins, and mucopolysaccharides. The inflammatory reaction often subsides within a few hours but may be followed by a delayed skin reaction. False-positive F-18 fluorodeoxyglucose positron emission tomography resulting from a bee sting has been described.