First, acute urinary tract infections, such as hemorrhagic cystitis or acute urethritis, can cause acute congestion and edema of the urinary tract mucosa, accompanied by bleeding. Secondly, the presence of urinary tumor, especially in elderly patients, can cause the whole process of carnal hematuria, which may not have any conscious symptoms in the early stage, but only the color of urine is red, and the further increase of tumor volume can lead to frequent urination or pain in the small abdomen, or pain in the area where the tumor is located. Cystoscopy and CT examination of the urinary system are needed to further confirm the diagnosis; thirdly, stones in the urinary tract, such as kidney stones and ureteral stones, can cause bleeding due to excessive friction of the mucous membrane of the stones, which can lead to acute blood in urine, usually accompanied by pain in the area where the stones are located, such as back pain or abdominal pain.