We have a replica of a bladder-shaped votive offering in our History of Medicine Collection. It is a copy of an original in the Science Museum's Wellcome Collection which dates to 200 AD.
These sorts of objects were left at healing sanctuaries and other religious sites as offerings to gods such as Asklepios, the Greco-Roman god of medicine. It was intended either to indicate the part of the body that needed help or to thank the god for a cure. They were made from bronze or terracotta. A large range of different votive body parts were made and offered up. Thousands have been found at archaeological sites.
You can listen to Professor Helen King, Professor Emerita of Ancient Medicine, Open University, talking about votive offerings here: