Red urine, also known as carnal hematuria, is usually considered for the following reasons: 1. Neovascularization of the external urethra, such as the urethral meatus visible in women. 2. Acute inflammation of the urinary tract, such as acute cystitis and acute pyelonephritis, patients can usually have frequent, urgent and painful urination. Patients with acute pyelonephritis may have symptoms such as chills, fever, and back pain, etc. When performing routine urine and blood tests, it is usually found that the white blood cell count is significantly elevated. 3. Painless carnal hematuria may be a typical symptom of urological tumors, and it is important to apply ultrasound or CT for screening to clarify whether it is a urological tumor. 4. Hematuria accompanied by severe pain, especially in the lumbar abdomen. Consider urinary system stones, especially ureteral stones. In addition, there are also urethral stones, and patients may have urinary disorders, dyspareunia, and painful involvement of the perineum and urethra during urination.5. Some systemic diseases, such as hematologic diseases, can also lead to hematuria, which is relatively complicated and requires detailed examination at the hospital.