Reducing artefacts in ambulatory urodynamics

To compare the diagnoses derived from a retrospective analysis of 50 ambulatory urodynamic recordings, unaware of the final diagnosis, and to evaluate the importance of the symptom diary and the presence of two transducers in the bladder rather than one.

Fifty women underwent ambulatory urodynamics (duration 4 h) after video cysto-urethrography. A single solid-state microtip pressure catheter was inserted with both transducers inside the bladder, and another was inserted in the rectum. The women were asked to complete a symptom diary and the results were analysed with the active participation of the patient. Detrusor 'instability' was diagnosed on ambulatory urodynamics if there was a simultaneous increase in detrusor pressure and in the 'urethral' line in the presence of symptoms (urgency or leakage). All 50 recordings were analysed retrospectively in four combinations, i.e. with and without the additional 'urethral' line displayed on the screen and with and without the diary information. The total number of detrusor contractions was then calculated for each reading and 'abnormal detrusor activity' diagnosed when a contraction occurred with or without symptoms as recorded in the diary. The final diagnosis for each reading was then compared with that made at the time of the test with the patient present.

Using the information from the diary reduced the number of pressure rises classified as 'abnormal detrusor activity' by 58%; using a second bladder pressure transducer further reduced the number of pressure rises classified as 'abnormal' by 19%. Overall, using both techniques together reduced the number of spurious pressure rises misclassified as 'abnormal detrusor activity' by 64%.

Both the symptom diary and the placement of two transducers in the bladder can decrease, by almost two-thirds, the diagnosis of pathological detrusor activity on ambulatory urodynamics.