The 3 oesophageal constrictions are:

• At the level of the cricopharyngeal sphincter (C6 vertebra).
• At the level of the aortic arch.
• At the level of the lower oesophageal sphincter.

On the frontal chest x-ray, the button battery is seen as a double ring (halo), whereas on the lateral chest x-ray, it has a step off. However, it may be difficult to differentiate between a coin and button battery on x-ray.

A button battery lodged in the oesophagus should be treated as an emergency and needs prompt removal.