My bunny is 7 years old and to date I have never noticed anything strange. His urine was occasionally too dark and I consulted a vet who said it is normal and according to her, it's getting darker with age, can be tinted by various foods, and if the bunny's behavior is otherwise normal, there was no need to worry. Today, late at night, when there is no possibility to contact any vet here until morning (it's a provincial town in Northern Spain, and only human emergencies are possible), I suddenly realized that he hasn't urinated for quite a long time. I also noticed in the last couple of days that he avoids juicy greens, which is quite unusual for him. He only takes a few bites of endive and leaves it to wither, which never happened before. Yesterday I offered him a tiny bit of banana and he just ignored it - for the first time in his life - which is another strange thing. Otherwise his appetite is quite normal in the context of hays and herbs. I gave him dry dandelion flowers and a piece of dandelion root and he ate with appetite. Is there any possibility to stimulate uropoiesis? how serious this situation can be?