Colon visualization of bone scan: a special and interesting case

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

AIM

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

PATIENTS, METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

A report on the incidence of intestinal 99mTc-methylene diphosphonate uptake of bone scans and a review of the literature

BACKGROUND

In addition to well-known specific conditions for soft-tissue uptake of bone-seeking radiotracers, there is a limited number of reports on intestinal uptake of (99m)Tc-methylene diphosphonate ((99m)Tc-MDP) on bone scans.

AIM

To describe the incidence of intestinal accumulation of (99m)Tc-MDP on bone scans in adult patients, define the patterns of this unusual finding and review the literature on its causes.

METHODS

Two thousand, one hundred and forty-four consecutive patients have been evaluated for intestinal (99m)Tc-MDP uptake on bone scans. Intestinal uptake was observed visually 3-4 h after the administration of the radiopharmaceutical. A whole-body bone scan and various spot views of the abdomino-pelvic region were obtained with a dual-headed gamma camera to evaluate the intestinal uptake. Delayed scans were also obtained as well as co-relative imaging and/or colonoscopic studies in some of intestinal uptake patients. Six patients had delayed scans of the abdomino-pelvic region. Fourteen patients had comparable scans either a year before or a year later. The positive intestinal uptake scans were further grouped according to the localization and intensity (mild uptake: lower than iliac bone; moderate uptake: equal to iliac bone; significant uptake: higher than iliac bone).

RESULTS

Twenty-two (17 female, five male) patients out of 2144 with a mean age of 57 years showed intestinal (99m)Tc-MDP uptake. The localization was mainly (20/22) in the right abdomino-pelvic region projecting on and in the configuration of ascending colon while one patient showed intestinal uptake all over the abdomen and one displayed diffuse intestinal radioactivity in his right hemithorax. The majority of the cases showed moderate to intense intestinal uptake (18/22). Six patients showed a decrease, disappearance or alteration in the intestinal uptake on the delayed images. Re-evaluation bone scans in five patients 1 year later showed no intestinal uptake this time. Among nine patients with prior bone scans 1 year before, intestinal uptake was negative in seven at that time. No significant pathology was obtained on the correlative images.

CONCLUSION

(99m)Tc-MDP uptake can be observed in the intestines in 1% of bone scans with a prominent localization in the ascending colon and rarely all over the intestines or in thorax due to Chilaiditi's syndrome, as well. The mechanism of intestinal uptake is still unclear in some of the patients. Delayed imaging, additional spot views and SPECT studies help in the differentiation of this finding from possible misinterpretation. Intestinal (99m)Tc-MDP uptake on bone scan could be an intermittent process and should be included among other well-known reasons of soft-tissue uptake.