An x-ray provided the problem and solution easily, but the path to it was not so easy, and could have had tragic results had it not been for the persistence 2-year-old Katie Smith's parents:

"We thought she was choking on a cracker at first, but my husband checked her airways and she was breathing fine," [Christina] Smith told ABC News today. "But she was gagging, drooling and holding her saliva, and she was crying and screaming, so we took her to a nearby hospital."

A doctor suggested Smith's 2-year-old had a flu or cold and sent her home, Smith said. She added that Katie's symptoms persisted, so she took her daughter to additional doctors, for other opinions.

According to Smith, the first four doctors said Katie likely had a flu or cold, but a fifth doctor at Toronto's Hospital for Sick Children ordered X-rays and discovered what was actually wrong: A small, circular, foreign object was lodged in Katie's esophagus, the tube that connects the mouth to the stomach.

"At first there were mentions of a plastic bottle cap, and then a coin, but then we got on the phone with an ear, nose, and throat specialist who said it could be a button battery," Smith said.

Doctors confirmed on Friday morning that Katie did swallow a lithim button cell battery when they removed it from her throat.  Her parents' persistence and following their intuition got the doctors to catch it in time for a good outcome:

"We learned the battery had corroded and burned through the first layer of her esophagus, which doctors said has three layer," Smith said. "There was some pus and swelling, but doctors cleared that up as well."

The mother added that her 2-year-old was "very lucky" and is now "doing great." Katie is now able to eat chocolate Popsicles and could start eating soft foods, like mashed potatoes, as early as tonight, she said.

Swallowing lithium batteries is more prevalent than you might think, Dr. Blake Papsin, the chief of otolaryngology, head and neck surgery at The Hospital for Sick Children explains to ABC News:

"Lithium batteries make up about 18 percent of the reported foreign bodies that kids swallow," Papsin told ABC News today. "They're everywhere. They're in hearing aids, phones, toys and in so much of the new technology."

...

"For some, they might not even know they swallowed it because it went right through the stomach and out the other end," Papsin said. "But when it does get stuck, it can cause corrosion. The electric current the batteries give off can produce toxic chemical reactions that damage and burn the tissue."

Papsin said that if a battery remained in an esophagus long enough, it could have the potential to perforate right through into the aorta and cause death.

Smith hopes her daughter's story helps encourage other parents to always "stick to your parental instinct" because "only you know your kids better than anyone else."

(via "X-Ray Reveals Lithium Battery Stuck in Toddler's Esophagus")