I was negative for UTI. But have white tissue in urine everytime I got. Once I had like a very small black rock and twice I had red tissue in urine. What is this stuff. I'm have a cat scan in 4 days. I have protien and leukoctye in my urine. My intestine area feels like knifes when the doctor presses on it. My right side of abdomen is very sore. What could all this mean?