Incidental 99mTc MDP uptake in the intestines and intravenous CT contrast

We evaluated the association between intestinal visualization on bone scintigraphy and IV CT contrast in patients with breast cancer.

452 patients with breast cancer underwent a 99mTc methylene diphosphonate (MDP) bone scan for surveillance of bone metastasis. Presence, site and intensity of intestinal uptake were visually assessed. For patients with intestinal visualization, medical records were reviewed to identify the alleged potential causes. When IV CT contrast was administrated on the same day as bone scan, the time between IV CT contrast injection, 99mTc MDP administration and bone scan was assessed.

Intestinal 99mTc MDP uptake was observed in 44 of the 452 patients (9.7%). Bone scans showed no thyroid or gastric uptake that suggested free pertechnetate. There were no patients with documented causes of intestinal uptake except for one patient with vesicoenteric fistula. Of the 452 patients, 149 (33.0%) underwent IV contrast-enhanced CT on the same day as bone scan. Forty of the 44 patients (90.9%) with intestinal uptake on bone scan underwent IV contrast-enhanced CT on the same day, whereas 109 of 408 (26.7%) patients without intestinal uptake on bone scintigraphy underwent IV contrast-enhanced CT on the same day (p < 0.001). The patients who underwent IV contrast injection between Tc-99m MDP administration and acquisition of bone scans had significantly more frequent intestinal uptake than patients who underwent IV contrast injection either before 99mTc MDP administration or after bone scanning (42.4% vs. 1.8%, p < 0.001).

IV CT contrast injection administered on the same day as bone scintigraphy is significantly associated with 99mTc MDP uptake in the intestines among patients with breast cancer.