Spontaneous phasic activity of the detrusor: a cause of uninhibited contractions in unstable bladders?

Uninhibited detrusor contractions of neurogenic origin have been described repeatedly. Since a spontaneous myogenic activity of the detrusor has been demonstrated in isolated muscle strips, it seems reasonable that an increase of this spontaneous contraction activity may induce bladder instability of pure myogenic origin. 30 patients separated into two groups were investigated. All patients suffered from involuntary contractions of the detrusor, accompanied by loss of urine. Nifedipin was applied as a selective Ca-antagonistic drug to block the phasic detrusor activity. In our experiment, involuntary detrusor contractions could not be suppressed, and also bladder capacity could not be increased by this drug. This result leads to the assumption that the spontaneous phasic activity of the detrusor does not induce any involuntary bladder contraction.