I have 3 cats and have some litter box issues. I used to have the covered boxes, but noticed that one of the cats was peeing outside the box. So I removed all of the lids. The problem seemed to stop, but then started again on occasion. I bought larger boxes, (I have three of them) and the issue still occurs. I finally discovered it was my cat with colitis. She does pee in the box, but gets so close to the edge or stands instead of squats that it goes outside the box. Is she doing this because of the colitis or a behavior issue? perhaps higher sided boxes would help? I keep the areas lined with pee pads, but they are no match for cat urine. Suggestions?