Once in the stomach, most ingested foreign bodies will pass spontaneously. However, there are notable exceptions which should be removed. What are they?

• sharp and pointed objects (associated with perforation rates 15 - 35%)
• objects longer than 5 cm 
• objects wider than 2 cm
• magnetS (pleural) or magnet with metal object 

Source

Felman: Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 9th ed.