Overview
Urodynamics is the investigation of the function of the lower urinary tract the bladder and urethra using physical measurements, such as urine pressure and flow rate as well as clinical assessment.
The assessment begins with a medical history and examination which may, for example, reveal abnormalities within the lower abdomen or pelvis that are contributing to the lower urinary tract symptoms.
The patient is then given a urination (voiding) diary to be kept for three days, to document their fluid intake and output, including episodes of incontinence.
- *bladder capacity
- *the frequency of passage of urine
- *episodes of incontinence
- *getting up at night to urinate.
The diary can also outline other problems, such as excessive fluid intake. A midstream specimen of urine is sent to the laboratory in order to exclude infection.
A pad test may be performed for women complaining of urinary incontinence. This test determines the severity of any incontinence and objectively demonstrates the symptom. The patient drinks 500ml of water and walks about performing normal everyday tasks, while wearing a pre-weighed pad.
The pad is then re-weighed and a gain of more than 1g per hour is taken to represent urinary incontinence.
What diagnosis can be made from urodynamic studies?
Urine produced in the kidneys is transported to the bladder by rhythmical contractions of the ureters.
At appropriate occasions the bladder is emptied via the urethra, by contraction of the normally relaxed detrusor muscle that constitutes the wall of the urinary bladder.
The detrusor muscle's behaviour is thought to sometimes become 'unstable', leading to the lower urinary tract symptoms such as problems with frequency, urgency and getting up at night to pass urine.
An unstable detrusor also contracts between voidings. This causes high pressures in the bladder that may be felt as urgency and give rise to urine leakage.
For obstruction, the International Continence Society has agreed that presently the only way to objectively diagnose it or grade its severity is a urodynamic pressure-flow study.
For incontinence the issue is more complicated. There are two main types of incontinence:
* stress urinary incontinence(SUI) that's caused by a deficiency of the closure mechanism of the bladder * urge incontinence that's caused by overactivity of the bladder. This overactivity can be demonstrated urodynamically by filling cystometry.