Blood in the urine of the cat is also a clear warning sign of cystitis. However, this symptom is very important because if the cat does not have cystitis. Blood in the urine indicates that something is wrong, you may have some other illness. In male cats, cystitis can cause complete blockage of the urethra, so that urination can stop completely. If you notice that your cat tries to urinate but can not, you may also suffer from cystitis.