In US slang, there is (to be) busting and the verb bust is a variant of burst. spec. To be desperate for the toilet. Chiefly with for or to. Also to be ready to bust. - OED. Apparently, it is still used in British slang also as OED provides examples from recent British publications. Here are the last two citations: More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.