Milk effective as gastrointestinal contrast agent
Michael J. Lander
Patients who have undergone CT imaging of their abdominal tract may have swallowed a barium-based solution before the procedure. The mixture -- usually a suspension of radio-opaque barium sulfate -- attenuates the x-ray signal from the machine and helps illuminate details of adjacent tissue in the images.
At the November meeting of the Radiological Society of North America, however, Dr. Lisa Shah-Patel from St. Luke’s-Roosevelt Hospital in New York presented results from an ongoing study that could help make cow’s milk an accepted radiological contrast agent for some patients.
Shah-Patel and her colleagues are studying the effectiveness of pasteurized, homogenized whole milk as compared with VoLumen -- a commercially available, diluted barium-sulfate-based formulation -- when taken orally prior to digestive tract imaging. They began the study about a year and a half ago as a logical extension of previous outside research that compared milk with barium-based agents, corn oil solutions and polyethylene glycol.
Researchers scanned patients who had consumed diluted barium-sulfate solution (left) and milk (right) as an oral contrast agent. Both patients also were administered an intravenous contrast agent. Arrows point to the small bowel. Bones and other regions that highly attenuate the x-ray signal appear white.
For the investigation, the researchers assigned adult patients to either of two groups. Sixty-two participants each drank approximately 1200 ml of the commercial agent, and 106 patients each received 600 to 1000 ml of milk.
Because both VoLumen and milk act as negative attenuation contrast agents --which cause the tract to appear gray rather than white -- radiologists administered an intravenous contrast agent during the imaging process to brighten blood vessels and the luminal lining. The team used a Toshiba CT detector or a single-slice CT scanner from Picker International (now Philips).
Two independent radiologists rated bowel distension on a scale of 0 (no distension) to 3 (excellent distension) for each individual, and bowel wall conspicuity on a yes or no basis.
Milk, they found, resulted in slightly less distension in some parts of the small bowel; the conspicuity of the images did not vary significantly between the media. Twenty-five percent of the patients who swallowed milk experienced discomfort after the procedure, compared with 42 percent for the barium-based solution. Clearly different was the cost of each agent -- $1.39 per patient for milk (purchased by the quart) and $18 for the barium-sulfate suspension.
The researchers are still enrolling patients to reach their target of 130 participants in each group, and final results are pending. “Right now, our study is only focusing on outpatients,” Shah-Patel explained. She noted that a greater diversity of cases would make the investigation more conclusive. Even after they finish their investigation, other institutions will have to conduct similar studies before milk can be approved for broader use.
Nonetheless, the team maintains that milk’s economy and tolerability could make up for its slightly poorer performance. “We’re finding that the future of milk in gastrointestinal imaging is very promising,” Shah-Patel said, stressing that the familiar beverage could play an important role for patients, especially children, who refuse to consume currently supplied formulations.
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