Cara- Some signs that your piggie may have a stone is peeing frequently, but only a small amount comes out at a time, crying or whining when peeing and/or pooing, or blood in his urine. There are probably other signs too, I'm sure other people can give you more info. You don't mention what makes you think your piggie has a stone, but the best thing to do if you think your piggie may have a stone is take him to the vet & get an x-ray to see if there is one actually in there. Hope this helps some. ***JAIME*** & Albert forever & always in my heart. http://www.piggiepages1.blinkz.com/