Nov. 28 (HealthDay News) -- Some obese patients who suffer complications after gastric bypass surgery are too big for CT scanners and other diagnostic imaging equipment, U.S. researchers warn.

They found that about 27 percent of patients weighing more than 450 pounds who needed imaging to diagnose a problem after surgery could not fit on the equipment.

"When patients weigh more than 450 pounds, standard diagnostic imaging often cannot be used. In these cases, physician must resort to other means of diagnosis, such as exploratory surgery or using less accurate or more invasive techniques," Dr. Raul N. Uppot, an assistant radiologist at Massachusetts General Hospital (MGH) and instructor of radiology at Harvard Medical School in Boston, said in a prepared statement.

He and his colleagues analyzed the cases of 44 patients weighing more than 450 pounds who had gastric bypass surgery at MGH between June 1999 and April 2007.

Of those 44 patients, 12 (27 percent) had post-surgical problems that required imaging but were denied because they were too heavy for the equipment. Some had to have surgery instead, while others had different kinds of tests.

The study was to be presented Tuesday at the annual meeting of the Radiological Society of North America, in Chicago.

"When obese patients cannot be diagnosed using standard-of-care imaging techniques, then other diagnostic measures have to be instituted. Patient care may be ultimately affected due to a compromised diagnosis," Uppot said.

About 140,000 gastric bypass procedures were performed in the United States in 2005, according to the American Society for Bariatric Surgery.

"When an obese person is contemplating gastric bypass surgery, he or she should consider that they will need follow-up imaging but may not be able to get the appropriate tests," Uppot said.

SOURCE: Radiological Society of North America, news release, Nov. 27, 2007