The main causes of urinary retention include urethral obstruction and decreased function of the forced urinary muscles. Urinary retention is a condition in which the bladder is filled with urine that cannot be expelled on its own. Urinary retention occurs mostly in older men. Urethral obstruction mainly includes prostate enlargement, caused by urethral injury, urethral stricture, and bladder tumors or bladder stones can also cause urinary retention. Functional decline refers to the difficulty in urination and subsequent urinary retention that arises with increasing age, or the weakness of the bladder contraction due to the decreasing function of the detrusor muscle caused by spinal trauma. Neurogenic bladder caused by diabetic patients is also a cause of urinary retention and needs to be differentiated from diseases such as prostate enlargement. Urinary retention is more harmful to the body and can lead to bladder rupture or hydronephrosis, which affects kidney function and is still very harmful to patients. The presence of urinary retention often requires catheterization, which is the insertion of a urinary catheter. In addition, after catheterization of acute urinary retention, too much urine cannot be discharged at once, which may cause hypotension and cause shock, and it should be discharged regularly. In summary, the etiology of urinary retention is mainly urethral obstruction and decreased function of the forced urinary muscle. Clinically, catheterization or cystostomy needs to be performed promptly when urinary retention occurs to first resolve urinary retention, further clarify the etiology, and treat the cause.