Changes in detrusor muscle oxygenation during detrusor overactivity contractions

To investigate changes in the oxygenated and deoxygenated haemoglobin (Hb) of the bladder wall during voluntary and involuntary detrusor contractions.

Women with lower urinary tract symptoms were recruited from a urodynamics clinic. Near infra-red spectroscopy, a non-invasive optical technique which monitors changes in tissue oxygenation, was used to measure oxygenated and deoxygenated haemoglobin simultaneously while the women underwent urodynamics. All data were compared using paired sample t-test.

Fifty-five women with a mean age of 52 years were enrolled into the study. In the 23 women with detrusor overactivity (15 with isolated detrusor overactivity and 8 with mixed urinary incontinence) there was a statistically significant rise in deoxygenated Hb during involuntary detrusor contractions at maximum detrusor pressure compared to the start of filling (p=0.02). There was no statistically significant change between Hb parameters measured at the start of the filling phase and those measured during voluntary detrusor contraction at pdetQmax (detrusor pressure at maximum flow rate). The mean detrusor pressure measured during voiding, however, was significantly higher than the maximum pressure during involuntary detrusor contractions (p=0.03).

There is a significant rise in the deoxygenated Hb in the detrusor muscle during detrusor overactivity, which is not seen during voiding even when the pdetQmax was higher than the peak detrusor pressure during involuntary contractions. These interesting changes in detrusor muscle oxygenation during involuntary detrusor contraction need to be explored further to assess if deoxygenation plays a role in the pathogenesis of detrusor overactivity.