Etiology and management of detrusor instability and mixed incontinence

The cause of detrusor instability and mixed incontinence remains elusive. Although DI is most prevalent at the extremes of age, GSI becomes more common with aging and child bearing, and therefore mixed incontinence is common, especially after menopause. Cystometry is used to diagnosis detrusor instability, but urethral closure pressure profilometry is required for assessment of mixed incontinence. DI is managed initially by behavioral therapy, and if this is not satisfactory then FES should be used depending upon availability. Drug therapy should start with oxybutynin at 2.5 to 5 mg twice-daily and increased as necessary to control symptoms. If the effects of therapy are minimal or side effects are too great, other medications or medication combinations should be tried. When the patient does not respond to this level of therapy, transvesical phenol injections should be considered, or, alternatively, a sacral selective neurolysis or neurectomy should be considered. Finally, invasive procedures will have to be considered starting with bladder transection, especially for the patient showing response to medication but intolerant of side effects. Mixed incontinence should be approached with conservative measures for each component. FES or imipramine therapy may help both conditions. If conservative therapy is not beneficial, surgical correction for GSI should be undertaken, with the knowledge that 35 to 50 per cent of patients will also have cure of DI, while the remainder can be treated medically for the DI.