arse like the top of a sauce bottle

Similar to the following: * Arse like a blood orange * Arse like a fresh bullet wound * Arse like the Japanese flag can be used to describe untold pain - often a burning sensation - when taking a dump. Spicy foods such as curry can impart such feelings and so too a bad stomach where it feels like you have taken to pissing out of your arsehole ( and the repeated wiping only serves to make it worse) It is a reference to the visual appearance of the top of a bottle of Heinz Tomato Ketchup. More specifically a large glass and well-used bottle as found in truckers cafes where the lid is often left off and the red ketchup congeals in to something somewhat unsightly.