Neurogenic Bladder Dysfunction
Expert: Dr Michael Whishaw
Michael was a founding member of the Continence Foundation of Australia and a past National Vice-President. He works as a Consultant Physician in Aged Care Medicine at Royal Melbourne Hospital. He has been a Consultant Continence Physician for more than 30 years, currently with the RMH Royal Park Continence Service and RMH Urology Service, and with special interests in incontinence in the elderly, neurourology in adolescents and adults, and urodynamics.
Watch the video
This video discusses the assessment and management of the neurogenic bladder.
Q&A with Michael Whishaw
Q: The new continence drug Mirabegron Beta 3 agonist - what side effects should we be aware of and what do we explain to clients and their carers about the use of the medicine?
A: Any side-effects are extremely unlikely in practice. The Consumer Medicine Information provided by the drug company says to check blood pressure due to a theoretical risk of raising the blood pressure, but this is quite negligible in the trial data. However, it should not be commenced in uncontrolled hypertension.
I think it always reasonable to monitor the residual volume at least in the short term, especially in susceptible patients (e.g. diabetics), but this is much less likely to be a problem compared with anticholinergics.
Mirabegron may enhance the action of some drugs such as metoprolol and digoxin, so if the patient is on these there is a need in the short term to confirm bradycardia or hypotension do not develop. Dose adjustments may be required for some other drugs including sotalol, amiodarone, ketoconazole, clarithromycin and erythromycin.
Mirabegron comes as 25 gm and 50 mg tablets and is prescribed as once a day therapy. It is a prolonged release tablet, so must NOT be cut, but both doses are the same price. $55 a month is a competitive price.
Q: What is the causative mechanism between stroke and OAB and the resulting symptoms of an overactive bladder?
A: Normal inhibitory neuronal pathways allow us to defer voiding till socially convenient. These inhibitory pathways may be damaged by stroke, leading to involuntary detrusor contractions and “OAB”. In acute stroke, there is usually a degree of oedema around the infarcted area. This oedema may contribute to the risk of this happening, but will settle with time, and so some will lose their OAB symptoms during stroke recovery.
Normal voiding occurs by suppressing the above-stated inhibitory pathway – i.e. we disinhibit to allow normal voiding to start, even without the urge to void being present. This ability to disinhibit can also be damaged in stroke, so that affected persons may not be able to initiate voiding, at least not unless they have the urge to void.
Q: Are different types of strokes associated with different types of incontinence?
A: The different types of stroke are infarction and haemorrhage. But it is the site of the stroke, rather than the type that influences the type of incontinence. The vast majority of strokes causing lower urinary tract symptoms, cause detrusor overactivity (urge incontinence, “OAB”). A very small number of stroke victims develop an underactive bladder, although in my experience this often improves.
Q: Are all spinal patients instructed to carry GTN with them at all times? Or is there a standard practice in relation to Autonomic Dysreflexia?
A: Autonomic dysreflexia only occurs with spinal lesions at or above T4-T6. All those with lesions in these areas should carry GTN. This is critical in those with spinal trauma. For lower lesions GTN is not required.
Q: When you mention radical pelvic surgery, can you expand on the type of radical surgery that you are talking about, e.g. radical prostatectomy, major surgery for bowel cancer & major gynaecological cancers and why these can cause urinary problems?
A: Major pelvic surgery may damage the pelvic nerves and cause detrusor underactivity or acontractility affecting bladder emptying. Occasionally stress incontinence may arise from damage to the innervation of the sphincter mechanism. Most cases are for gynaecological or distal bowel cancer, but can be for benign disease such as a ruptured diverticular abscess. Such outcomes occasionally also occur after hysterectomy for benign disease.
Radical prostatectomy may result in stress incontinence, but will not directly affect bladder function.