Each year, about 3,500 button battery swallowing cases are reported to the U.S. poison control centers. Serious injuries and deaths are on the rise. The most serious cases involve nickel-sized 20 mm diameter batteries. These can get stuck in a child's throat and burn through the esophagus in as little as two hours. Repair can require feeding and breathing tubes and multiple surgeries. Kids under age 4 are at greatest risk.