Video-urodynamic characteristics of non-neurogenic, idiopathic underactive bladder in men – A comparison of men with normal tracing and bladder outlet obstruction

OBJECTIVE Underactive bladder is frequently encountered in elderly patients. It may result from detrusor underactivity (DU) or low detrusor contractility due to a urethral sphincter inhibitory effect. This study analyzed the video-urodynamic study (VUDS) characteristics of patients with underactive bladder in a large cohort of men with lower urinary tract symptoms (LUTS). METHODS Male patients with LUTS who had failed the initial treatment were consecutively enrolled. All patients underwent detailed urological investigations including prostate measurement, free uroflowmetry, post-void residual volume (PVR) measurement, cystoscopy and VUDS. The VUDS characteristics of the men with underactive bladder were analyzed and compared with those of men with bladder outlet obstruction and normal tracing. RESULTS A total of 1329 men who underwent VUDS were included in this retrospective analysis. After VUDS, the final diagnosis was DU in 165 patients, poor relaxation of external sphincter (PRES) in 525, bladder outlet obstruction in 501, and normal tracing in 138. VUDS findings in DU patients showed a slowly increased detrusor pressure, intermittent detrusor contractions, or early decline of detrusor contraction, resulting in a low maximum flow rate (Qmax), and large PVR. In comparison with the PRES groups, DU patients were older, had reduced bladder sensation, lower detrusor pressure (Pdet), lower Qmax, larger PVR volume, and lower voiding efficiency. Patients with urodynamic PRES also had low-pressure-low-flow tracings, but their bladder sensation was similar to that with normal tracing. DU patients with very low Pdet also had low detrusor tonicity, and more medical co-morbidities than the other groups did. CONCLUSION Idiopathic underactive bladder in elderly men could be attributed to urodynamic DU and PRES. DU is associated with old age, reduced bladder sensation, low voiding efficiency, and medical co-morbidities.