I'm so sad to hear that Bjorn. Pets are part of our families and are so special. And each one has a special personality that you simply can't replace just buying another cat or dog.
My brother's dog, pushing eleven years old decided recently to eat a tennis ball that was as large as his head. (He's a maltese terrior). He had played with his tennis ball for years and never hinted he would eat it. Once in his stomach in bits and pieces, it got stuck. Surgery to remove it cost several thousand, but for the whole family it was money well spent.
Once a pet's quality of life deteriorates, one really has to have the animal put down, because otherwise it's just cruel. We've had to make this choice ourselves and it's always a difficult and emotional time.