My rabbit died during the night

Question
My rabbit had not been eating properly the day before he died, he was sitting in the corner of his hutch and had urinated twice when we brought him into the house, this time it was very large amounts and was orangey in colour, two days prior to this he looked fine with no real change in behaviours, can you tell me what you think he died of?

Answer
Orange urine is actually completely normal in rabbits, and is not a sign of disease. Some rabbits have it often, some only have it once in a while.

It is very difficult to determine the exact cause of death without more information, and even then, only a necropsy (post-death look at the rabbit) could give you a sure answer unless one of the signs was obviously pointing toward one problem or another. However, since you mentioned that he was not eating, my first guess would be problems with his digestive system. Rabbits have a very delicate digestive system. If a rabbit goes into gastrointestinal stasis, AKA G.I. stasis, (where the gut stops working properly), death can follow pretty quickly. G.I. stasis can be caused by the gut being empty or less full than it should be, so if he ate poorly the night before, that could have caused it. Now, why he wasn't eating properly is hard to determine without much more information.

Were his feces looking normal, or were they runny or smaller than normal? Or had he stopped producing feces altogether? Did they have strings of hair in them?

Were his eyes and nose clear of mucus and looking healthy?