When oxalates enter the bloodstream and filter through the kidney to enter the bladder, they can form crystals. These oxalate crystals are thought to resemble broken glass structures, which irritate the bladder lining and potentially attach to glycoproteins and form bladder calculi. Following a low oxalate diet can help to reduce exposure to certain foods that are high in oxalates which in turn will decrease irritation to the bladder, bladder pain, urgency, or frequency.

https://icwellness.org/blog-post/are-oxalates-to-blame-for-your-ic-pain/