In patients with urinary retention who require indwelling catheterization, intermittent urine release is required, and the urine should not be emptied at once and cause bleeding from the bladder mucosa, resulting in carnal hematuria. For patients with urinary retention, the volume of urine should not exceed 600ml the first time after indwelling catheterization; thereafter, the volume of urine should be released every hour at intervals of about 400-500ml until the urine in the bladder is completely emptied. If the urine is emptied at once after indwelling catheterization, the pressure in the bladder drops abruptly, which can cause the small blood vessels on the bladder mucosa to rupture and bleed. At this time, the patient may show a full course of flesh-eye hematuria, and patients with more serious bleeding may even cause a hematoma to form in the bladder, blocking the urinary catheter and causing an undrainable situation. Therefore, for patients with indwelling catheterization, if a large amount of urine is stored in the bladder, it is recommended to release urine intermittently, with the volume of each release being about 400-500 ml and the interval being about 1 hour.