As a pediatric nephrologist I see a lot of cute kids with kidney problems. My favorite and cutest patient is our family cat, Denver. Late in 2007 he was diagnosed with chronic kidney disease, a common cause of death in elderly cats (he just turned 17 years old). He was not overly fond of the kidney diet, and sneaking potassium supplements into his food was impossible.
This spring we began the "interesting" task of administering subcutaneous fluid every 2-3 days. Since starting this course, his weight has stabilized and he has periods of feisty playfullness again. While his days are numbered (I don't know what 17 is in cat-years), he is still enjoying life. Of course, he is crotchety enough that he has decided to only eat Fancy Feast in turkey flavors, but I hope someone will humor my preferences when I reach an advanced age!
For more information on chronic kidney disease in cats, go to http://www.felinecrf.com/