FEMALE UROLOGY

Urodynamic verification of an overactive bladder is not a prerequisite for antimuscarinic treatment response
Malone-Lee J, Henshaw DJE, Cummings K
Department of Medicine, Whittington Hospital, Royal Free and University College Medical School, London, UK, Department of Medicine, Kalgoorlie Regional Hospital, Kalgoorlie, Western Australia, Australia, and Department of Geriatric Medicine, Homerton Hospital, London, UK
BJU Int. 2003; 92: 415-7

• Objective: To investigate the place of urodynamics in the evaluation of patients with symptoms of the overactive bladder by comparing the response to antimuscarinic therapy in those with and with no urodynamically verified symptoms.
• Patients and Methods: In a prospective observational study, 356 female patients with urinary frequency (> 8 voids/24 h) and urgency, with or without urge incontinence, underwent cystometry. Patients were diagnosed with detrusor instability if there were spontaneous uninhibited increases in detrusor pressure during bladder filling. All patients regardless of urodynamic findings were subsequently treated with oxybutynin 2.5 mg twice daily and bladder retraining. The outcome was evaluated as the change in urinary frequency and incontinence episodes after 6-8 weeks of treatment.
• Results: Among 352 evaluable patients, 266 (75%) had detrusor instability on cystometry and the remainder did not. There was no significant between-group difference in mean age, urinary frequency or the number of incontinence episodes at presentation. Both groups improved equally well during oxybutynin and bladder retraining therapy; after 6-8 weeks there was no significant between-group difference for the mean change from baseline in urinary frequency or incontinence episodes. Tolerability profiles were comparable to the two groups.
• Conclusion: Patients with symptoms of an overactive bladder, but apparently normal urodynamic findings, respond equally well to antimuscarinic therapy as those with urodynamically verified symptoms. Such findings cast further doubt on the clinical validity of using invasive urodynamic procedures to characterize patients with irritative lower urinary tract symptoms before starting antimuscarinic therapy.
  
  
• Editorial Comment
  The authors performed a prospective observational study of 356 female patients who reported to their office with urinary frequency and urgency with or without urge incontinence. The authors performed cystometry on the patients and identified those patients with detrusor instability on cystometry and those who did not have detrusor instability. Regardless of cystometric findings, both groups of patients were treated with oxybutynin 2.5 mg twice daily and bladder retraining. Response to therapy was then evaluated for both groups with the results indicating no significant difference between the groups for the mean change from baseline in urinary frequency or incontinence episodes. The conclusion of the authors is secondary to the symptomatic response of patients with apparently normal urodynamic findings; an examination of the value of urodynamics prior to instituting antimuscarinic therapy should be entertained.
  The authors raise a valuable point in discussing the need for pretreatment testing in the therapy of the overactive bladder. That a significant number of patients had no detrusor instability on cystometry but still responded to oxybutynin is not surprising; for as Dr. Edward McGuire stated “A routine cystometrogram used to make the diagnosis of detrusor instability is a blunt instrument: if negative, it does not rule out the condition” (1). To put it in other words, that a patient with detrusor instability has a negative CMG is not unusual in view that 50% of patients with motor urgency have a negative CMG. In addition, secondary to this noted phenomenon, there are numerous tactics described in the literature to help increase the cystometric yield rate including a rapid fill (> 100 cc/min) or if the patient is asked not to try to void or prohibit micturition during the filling phase (2). In view of the accepted limits of cystometry, it is clear that this article helps us remember that cystometry does not take the place of clinical judgment but is merely another tool to help clarify the patient’s diagnosis prior to instituting therapy. Is it needed absolutely in all cases of OAB? No. Should it be considered by the specialist in complex cases? Yes.

References
1. McGuire EJ: Bladder instability and stress incontinence. Neurourol Urodyn. 1988; 7: 563-7.
2. Blaivas JG, Groutz A, Verhaaren M: Does the method of cystometry affect the incidence of involuntary detrusor contractions? A prospective randomized urodynamic study. Neurourol Urodyn. 2001; 20: 141-5.

Dr. Steven P. Petrou
Associate Professor of Urology
Mayo Medical School
Jacksonville, Florida, USA