Urinary Flow Studies
Our main consulting suite at Norwest Private Hospital has a treatment room, run by our Clinical Nurse Specialist, Margaret Troup.
Urinary flow studies are performed in most men with prostate flow problems, or other non-specific lower urinary tract symptoms. A urinary flow study is a simple treatment room study, where the patient is asked to come to the rooms with a relatively full bladder and passes urine in a private treatment room setting, into a funnel system, which then measures the urine flow in mL/s. The normal male urinary flow should be 25-30mL/s. An obstructed flow rate is < 10-12mL/s and this may relate to prostatic enlargement and prostatic blockage.
Other causes of urinary blockage include a urethral stricture, which occurs in patients that have had previous urethral catheterisation or instrumentation, urethral trauma or urethral infection. The urethral stricture flow typically is a flattened curve, with a rate of 3-4mL/s, as distinct from prostatic obstruction, which tends to be between 5-10mL/s (Qmax).
We perform formal urodynamics, which is the more formal way of measuring and quantifying the relationship between the prostate/bladder neck outlet and the upstream bladder. Urodynamics requires the urine to be non-infected and sterile, which is tested in the rooms by way of a urinalysis dipstick. Antibiotic coverage is given by way of oral tablets for a short period of time. The patient is managed in our treatment room and our practice nurse places a urethral bladder filling catheter, containing a pressure transducer and connects it to the urodynamic machine, as well as a rectal pressure line, also connected to the machine.
The urodynamics machine and software are able to calculate and project onto a printout the pressures developed within the bladder, in relation to the prostatic bladder neck outlet, during the voiding cycle. Urodynamics is simply divided into the (i) filling phase and the (ii) voiding phase. The bladder is filled with normal saline, through the urethral filling line and bladder pressures are monitored. When bladder capacity is reached, the patient is asked to void with the urethral and rectal lines remaining in place. The peak bladder wall pressure is recorded during the voiding phase and in particular at the time of maximum urinary flow (Qmax), and a pressure flow equation is used to generate a figure that can confirm or exclude either prostatic outlet obstruction or bladder detrusor overactivity/instability.
Urodynamics are of key importance prior to committing certain patients to definitive prostate TURP surgery. Urodynamics are also of key relevance in the ongoing assessment of an unstable irritable or overactive bladder, in particular in the decision making of oral, transdermal, or intravesical injection therapies, for detrusor instability.
Urodynamics must be used prior to committing a patient to definitive artificial urinary sphincter (AUS) cuff surgery in the male post-prostatectomy incontinence setting. They are also used in the assessment of the neurogenic bladder.