A recent Google search on snails found a medical case report* about a 74-year old Spanish woman who had a snail shell stuck in her ileum, the terminal portion of the small intestine. The woman had swallowed the shell accidentally while apparently eating a Spanish dish called paella that contains snails. The woman was suffering from abdominal pain and vomitting when she was admitted to a hospital. Various scans revealed a foreign object in her abdomen, which was removed surgically and turned out to be a snail shell.
Here is a radiograph showing the shell in situ and a photo of it after removal.
Fig. 3 from Lerma et al., 2002.
I am not familiar with edible snail species of Spain, but this one may be an Otala sp. or perhaps, Eobania vermiculata. It's amazing that the woman swallowed the more than 3-cm long shell intact. She was lucky it didn't get stuck in her windpipe.
*Lerma, Marcos Agramunt; Mariscal, José María Errando; Cordón, Fructuoso Delgado; Abril, Segundo Gómez; Orón, Eva Montalvá; Pérez, María Jesús Martínez. 2002. Small Bowel Obstruction Caused by Snail's Shell: Radiographic and CT Findings. Journal of Computer Assisted Tomography 26:529-531. Abstract