What is Battery Ingestion?

In recent years, our electronic toys and gadgets have become increasingly miniaturized. Their power requirements are being met by a new generation of compact, high-performance batteries. These disk batteries are small, pill- or coin-shaped devices that contain heavy metals such as zinc, mercury, silver, nickel, cadmium, and lithium. They also contain concentrated solutions of caustic electrolytes, usually potassium or sodium hydroxide. Their compact size and harmless appearance hide their true danger. The danger comes when children (and sometimes adults) knowingly or mistakenly put these tiny batteries in their mouths and swallow them. Most swallowed batteries cause no problem.
  • Batteries lodged in the esophagus (the food pipe between mouth and stomach) must be removed immediately. They cause damage by their pressure against the wall of the esophagus, from leakage of caustic alkali, and the electrical current they generate. Injury can occur in as short a time as one hour. Full-thickness burns can occur in four hours. Batteries passing through the esophagus usually pass uneventfully through the entire digestive tract.

    Source: http://www.emedicinehealth.com