Bleeding after urethral insertion, according to clinical experience, may have the following causes: 1, the patient itself has urethral stricture or prostatic hypertrophy squeezing the urethra, which makes the process of catheterization more difficult. 2, the problem of catheter material, inappropriate catheter type, rough action of the operator or not applying enough lubricant during operation. 3, after catheterization in patients with urinary retention, short time emptying of the bladder can cause decompressive hematuria. 4, some patients may be accompanied by chronic cystitis, bladder tumor, bladder stone, renal pelvis tumor, or coagulation mechanism disorders, long-term use of anticoagulant drugs and other underlying diseases. . 4, Some patients may have chronic cystitis, bladder tumor, bladder stone, renal pelvis tumor, or coagulation mechanism disorder, long-term use of anticoagulant drugs and other underlying diseases.