Damage is from sodium hydroxide generated by electric current, not from leakage!
Should be recognised as a medical emergency, deaths have occurred.
Haematemesis, haemoptysis and respiratory difficulties can manifest up to 28 days after ingestion of the battery, so easy to miss or ignore. Given the age of the children involved, they are unlikely to tell you! Catastrophic aortooesophageal fistula possible, as in the case of Hugh McMahon in Lanarkshire. Earliest perforation has been at 12 hours – median is 5 days. [Am J Emerg Medicine 2019]
Removal of the battery alone may be insufficient action to prevent further damage, with further symptoms manifesting later; patients need expert input, and careful monitoring and follow-up. One further incident described the death of a child from late complications after they had been treated and sent home.
US Poisons centre recommends use of honey or sucralfate if ingestion within the last 12 hours.