Invasive urodynamics can provide a wealth of clinical information but also has potential complications including a 2-10% risk of infection(1). For this reason, EAU, AUA and NICE guidelines(2) have recommended that invasive urodynamics should be deferred in the investigation of lower urinary tract symptoms(LUTS) unless operative treatment is being considered. 
Within the UK, the majority of patients complaining of storage lower urinary tract symptoms are managed by general urologists rather than those with a functional urology interest. This coupled with the rotational system of junior urological residents means that several unwarranted referrals are made for invasive urodynamics. 
We reviewed our trusts use of urodynamics and its impact on clinical outcome. We then changed the referral pathway and reaudited our results.

We retrospectively reviewed all invasive urodynamics performed at our trust over a 4 month period. Our primary measures were the indication for the investigation and how many patients were subsequently listed for surgery. Our secondary measures included pre-urodynamics investigations(flowmetry, post-void residual and urinalysis) and management(use of medications, physiotherapy and bladder retraining).

We then introduced a new paper referral system(figure 1) which mandated several stipulations be met. 
Following these changes, a blinded second investigator reviewed one month of data using the same methods.

48 patients were listed for invasive urodynamics between 06/07/17-19/10/17.  13 patients were excluded due to non-attendance, infection or patient choice.  

Our cohort consisted of 23 patients with storage LUTS, 3 complaining of stress urinary incontinence, 7 were of mixed urinary incontinence and 2 patients had suspected detrusor underactivity.  More than half of this cohort did not have any prior flowmetry or urinalysis and 40%  did not have any documented postvoid residual. 

77% of patients with storage LUTS had not been tried on maximal medical management(anticholinergic and or mirabegron) and of this group only 34% of patients were listed for surgery as a consequence of urodynamics. None of the patients complaining of stress urinary incontinence had undergone physiotherapy supervised pelvic floor exercises and only one patient was referred for operative intervention.  Of the mixed incontinence cohort only one patient fulfilled the criteria of trialling maximal medical therapy and physiotherapy supervised pelvic floor exercises. 86% of the mixed incontinence group did not proceed to invasive treatment. 

Following the new referral system over 80% of patients had underwent a prior flow rate and post void residual. Moreover over 60% of patients were referred for invasive intervention as a direct outcome of the urodynamics.

Our study has demonstrated that a significant proportion of our LUTS patients were not being fully evaluated with flowmetry or a postvoid residual. Moreover a significant number had not exhausted all of the conservative or medical therapies available and as a consequence were arguably undergoing invasive urodynamics prematurely. This is supported by the fact that the vast majority did not proceed to operative interventions. 

Following our new referral system there were clear improvements. A larger proportion of patients had undergone maximal medical therapy and most had documented non invasive urodynamics. Most patients who had invasive urodynamics were referred for operative intervention as opposed to 31% in the first study.

Although there is a debate regarding the clinical utility of urodynamics , there is no doubt that it should only be performed with a clear indication and in the context of full understanding of the clinical problem. Regardless of the current consensus regarding the optimal timing of invasive urodynamics it is crucial that each urological department sets its own indications.  This study has demonstrated that the majority of patients have not proceeded to surgical treatment following invasive urodynamics and have opted for conservative and medical management. In this context, invasive urodynamics could have been delayed until they had tried all conservative and medical management as hypothetically some may have been cured and not needed further investigation. The use of a urodynamics referral system encompassing a set criteria  provides a sustainable and reproducible method to prevent unnecessary tests.

British Association of Urological Surgeons (June 2017), Urodynamics Patient information sheet. Retrieved from http://www.baus.org.uk/_userfiles/pages/files/Patients/Leaflets/Urodynamics.pdf
Winters et al(2012), Adult Urodynamics: AUA/SUFU Guideline. Retrieved from http://www.auanet.org/guidelines/urodynamics-(2012)