AIMS OF STUDY:
In idiopathic detrusor instability an objective diagnosis is made with urodynamic investigations. The severity of the patients' symptoms of urge and frequency correlate poorly with urodynamic findings [1]. Traditionally detrusor instability has been the main focus for diagnosing patients and directing their management. Little progress has been made with the evaluation or management of the sensations of urge. The presence of an indwelling catheter can produce the perception of urge [2] which may confound the urodynamic assessment. We have developed a more objective measure of the sensations perceived by patients during filling cystometrograms. The aim of this study was to compare the graded scores of sensations of urge recorded by the patients in voiding diaries with the same graded urge scores measured objectively during filling cystometrograms.

METHODS:
5 patients with an established diagnosis of idiopathic detrusor instability were studied. Medication prescribed for an overactive bladder was discontinued. Patients completed a voiding diary for one week. In this diary they recorded the measured volume of each void, whether they felt empty after voiding and the degree of urgency prior to voiding. The degree of urgency was scored from 0 to 4 where 0 = no urge, 1 = mild urge, 2 = moderate urge, 3 = strong urge and 4 = "desperate" urge. Patients then attended the urodynamic department for medium fill cystometry. Serial CMGs were performed and during each CMG a keypad device was used by the patients to score their levels of urge, according to the same scale used in the diary. The keypad device enabled patients to signal their sensations without prompting by, or discussion with, the investigator. The urge score was continuously recorded on our standard urodynamic equipment. Sensations recorded in diaries were then compared to those obtain during CMGs.

RESULTS:
Correlation between the 4 point urge score recorded in voiding diaries and the urge score recorded during filling cystometry was good in 4 patients. In the other patient, bladder volumes recorded during urodynamics were less than those recorded in the diary for each urge level scored. It is possible this effect was due to catheter interference. All other patients did not consider that the catheter interfered with their perception of bladder sensation.

Figure 1. Graphs A and B are plots of mean bladder volumes and SEM against urge score from individual patients. Graph C shows mean bladder volume and SEM at urge scores 1-3 (n=4). This data is from the 4 patients' in whom urge scores derived from both diaries and urodynamics compared well. This data has been normalised around urge level 3. One patient may have had altered perception of urge during urodynamics due to catheter irritation (graph B).

CONCLUSIONS:
There is a clear trend in 4/5 patients of comparable urge scores when these scores are obtained by voiding diaries or objective urodynamic investigation. Evaluation of the sensations of urge are essential for a systematic approach to patient management. This more objective assessment of patients' sensations of urge during filling cystometrograms is a useful tool for diagnosis and surveillence of treatments in patients with detrusor instability. However, interpretation of sensations during urodynamics must remain cautious and must be supplemented with a thorough voiding diary.

S Oliver's research is sponsored by Medtronic Inc.