The common causes of residual urine include benign prostatic hyperplasia (BPH), urethral calculi, weak bladder muscle contraction, and prostate cancer. 1. benign prostatic hyperplasia: benign prostatic hyperplasia patients can be due to the hyperplasia of the prostate gland pressure urethra, resulting in urine outflow obstruction, causing part of the urine residual in the bladder, resulting in the phenomenon of increased residual urine in the bladder. 2. Urethral calculi: The obstruction of calculi may cause the urine to be unable to be discharged smoothly, resulting in an increase in the amount of residual urine in the bladder. 3. Weakness of bladder muscle contraction: for example, cerebral hemorrhage, cerebral infarction, diabetes mellitus, etc. can cause weak bladder muscle contraction, which will lead to the phenomenon of increased residual urine volume in the bladder. 4. Prostate cancer: prostate cancer can also cause frequent urination, urinary urgency and difficulty in urination, which leads to the obstruction of urination and thus the phenomenon of increased residual urine volume in the bladder. There are many other reasons that can lead to the phenomenon of residual urine, it is recommended to go to the regular hospital, cooperate with the doctor to improve the examination, clarify the cause, and actively deal with it.