What is urodynamics? Urodynamics is a new discipline that studies the function of the urinary tract in transporting, storing and discharging urine with the help of fluid dynamics and electrophysiological methods. It was formed in connection with modern electronic and measurement technologies. Urodynamics can provide an objective basis for the diagnosis, selection of treatment and evaluation of the efficacy of patients with voiding disorders. Urodynamics is subdivided into two parts: upper and lower urinary tract urodynamics. The former focuses on the transport of urine in the renal calyces, renal pelvis and ureter, while the latter focuses on the storage and discharge of urine in the bladder and urethra. Lower urinary tract urodynamics is more widely used in clinical practice. Commonly used urodynamic techniques include: ① measurement of urinary flow rate; ② measurement of various pressures; ③ determination of electromyography; ④ dynamic radiological observation, etc. Why is it necessary to undergo urodynamic examination? The most important thing is to understand the functional status of the vesicourethra, because different functional status may lead to the same external manifestations. For example, the same child with neurogenic bladder incontinence may have filling incontinence due to weak contraction of the detrusor muscle, and the same child may have urge incontinence due to overactivity of the detrusor muscle, but the two are treated completely differently. The purpose of urodynamic examination is to distinguish between these causes, to detect the corresponding morphological and functional changes of the bladder and sphincter by simulating the real voiding situation of the child, to provide a clinical basis for the diagnosis of voiding dysfunctional diseases, and then to provide objective material for the treatment and prognosis of the treatment effect. Which children need urodynamic testing? Patients with neuropathies that may be combined with abnormal vesicourethral function, such as cremasteric bifida, cremasteric bullae, and cremasteric dysplasia. Patients with lower urinary tract symptoms or functional abnormalities, such as urethral valves and anorectal anomalies. Patients with non-neurological congenital disorders with possible abnormal vesicourethral function, such as enuresis, abnormal functional voiding, and vesicoureteral reflux.