Lower urinary tact symptoms (LUTS) in men aged over 60 years are often assumed to result secondary to bladder outlet obstruction (BOO) caused by benign prostatic hyperplasia. However in younger men, LUTS may be secondary to  a wider variety of underlying causes. These include BOO caused by bladder neck obstruction, prostate, non-relaxing sphincter (dysfunctional voiding) and/or strictures. In addition these patients may have primary idiopathic detrusor overactivity (DO) or DO secondary to the BOO resulting in or exacerbating the storage symptoms. 

The aim of our study was to prospectively assess the video urodynamics (VCMG) presentation of men under 50 years-old with refractory LUTS.

We evaluated the presenting symptoms and VCMG data of 131 consecutive men aged 18-50 years (median 39 years). These men were referred to our tertiary referral centre for medical therapy refractory LUTS. Patients with known neurogenic bladder dysfunction were excluded. 

Using the bothersome symptom in the patient's history, we categorised the patients presenting symptom as either primarily storage or voiding. 

All urodynamic studies were performed in accordance to the ICS Good Urodynamics Practice document. All urodynamics data was assessed for quality and if the patient reports that the study has been representative before inclusion into analysis. Urodynamic parameters included the presence of DO and bladder compliance. Bladder wall compliance was classified as reduced if the bladder compliance index C, calculated as the change in bladder volume divided by the change in detrusor pressure, is less than 40 ml/cmH2O. The void was classified as obstructed if the bladder outlet obstruction index (BOOI) was greater than 40 using the International Continence Society (AG) nomogram. To localise the site most likely flow-limiting region, the voiding images were studied. Radiographic evidence of external sphincter activity in the presence of a sustained detrusor contraction was used as the diagnostic criteria for the diagnosis of dysfunctional voiding.

The presenting symptoms were primarily storage and voiding in 78% (n=102) and 22% (n=29) of patients respectively. 6 men were unable to void during the study. Of the 125 men with voiding phase data, 49.6% (n=62) of patients demonstrated BOO. The aetiology of BOO were bladder neck obstruction in 43.5% (n=27) of men, a non-relaxing external sphincter (dysfunctional voiding) in 32.3% (n=20). Unsuspected urethral stricture were noted in 6 men. Prostatic obstruction was observed in 9 men. Idiopathic DO and/or reduced compliance was demonstrated in 53 men (43%). However, only 28 (52.8%) of the with DO were demonstrated as being urodynamically obstructed.

Although the presenting LUTS are primarily storage in 78% of men aged <50 years, almost half demonstrate BOO. The etiology of the BOO observed in this cohort are wide-ranging. In this cohort, accounting for almost half of obstructed men, the most like cause of obstruction is the bladder neck. 

Dysfunctional voiding, where flow is impeded by either intermittent or total non-relaxing external sphincter acitivity, accounts for almost a third of BOO causes. Patients with dysfunction have over-lapping presenting characteristics to patients with other BOO aetiologies and only the use of voiding fluoroscopic video and concurrent pressure-flow data was shown to reliably determine the cause for the poor flow. 

 Although IDO is often suspected as primary cause for filling phase LUTS in "young" men, our result indicate less than half of these patients demonstrated DO suggesting the storage symptoms are just as likely to resulting from in efficient voiding and associated incomplete emptying. Furthermore, only half of the men with idiopathic detrusor overactivity demonstrated BOO. This suggest that the often causal perception of BOO in resulting in DO may not be a strong in "younger" men.

The underlying cause of LUTS in men aged <50 years are less predicatble than in older men. Video urodynamics is recommended for accurate diagnosis of the cause of the BOO.