First of all, what is hematuria? In layman’s terms, it is the presence of blood in the urine. If every 1000 ml of urine contains more than 1 ~ 2 ml of blood, the naked eye can see the urine is red or wash water color, it is called hematuria; if the naked eye without urine color abnormality and under the microscope to see red blood cells in the urine, it is called microscopic hematuria. Then what is “painless hematuria”? That is, in addition to hematuria, often without pain and other symptoms or discomfort. Hematuria is the most common symptom of urological diseases, and the first symptom of many urological diseases is hematuria, while “painless hematuria” is usually regarded as an important warning signal of urological tumors, which should be taken seriously. The most common tumor is bladder tumor, which accounts for more than half of urinary tract tumors; secondly, renal pelvis/ureter tumor is an important cause of “painless hematuria”. Because hematuria caused by uroepithelial tumors is often intermittent, sometimes hematuria can disappear without treatment, and it is easy to be ignored, thus delaying diagnosis and treatment. Therefore, if painless hematuria occurs, even if it is only once, you should go to the hospital for further examination. There are many other causes of hematuria: prostate cancer and prostate hyperplasia patients may also experience “painless hematuria”, but it is often accompanied by obvious symptoms such as frequent urination, urinary urgency, urinary pain or difficulty in urination. In addition, various types of nephritis, pyelonephritis, polycystic kidney, urinary stones, infection, tuberculosis, blood diseases can also cause hematuria, some drugs (sulfonamides, salicylic acid drugs and anticoagulants) can also appear in the urine red. So even if hematuria occurs, do not worry too much, should consult a doctor to find out the cause.