Evaluating ambulatory urodynamics: a prospective study in asymptomatic women Stefano Salvatore a , Vik Khullar a , Linda Cardozo a, * , Kate Anders a , Gaia Zocchi b , Marco Soligo b Objective To identify abnormal detrusor contractions in asymptomatic women undergoing ambulatory urody- namics, to standardise the investigation technique for women with urinary symptoms for clinical practice. Design Prospective observational study. Setting Two tertiary referral urogynaecology units: one in London, UK and one in Varese, Italy. Methods Women without urinary symptoms were recruited into the study. Ambulatory urodynamics was performed according to the King's College Hospital protocol. All the traces were analysed in four different ways: 1. without the second bladder transducer measurements displayed on the screen and without the diary; 2. as in 1. but with the diary; 3. with the second bladder sensor displayed on the screen but without the diary; 4. as in 3. but with the diary. The diary was always interpreted at the end of the test with the woman present. For each method we reported the total number of detrusor contractions and whether the woman would have been diagnosed as having abnormal detrusor contraction. Cochran's Q test was used for statistical analysis. Results Twenty-six women (mean age 31.7 years) were recruited. Ambulatory urodynamic testing lasted an average of 3.57 hour. The diagnosis of abnormal detrusor contraction varied by 65.4% depending on the method of analysis used. The diary and the women's symptoms during the test were the most discriminating factors. A signi®cant difference between the diagnoses was obtained when comparing the four different ways of analysis. According to our protocol only three women (11.5%) had abnormal detrusor contractions. Conclusions Using our protocol almost 90% of asymptomatic women have a stable bladder on ambulatory urodynamics. This is similar to the results of labouratory urodynamic testing of asymptomatic women but is in contrast to previous reports of ambulatory urodynamics of asymptomatic women. The technique used during ambulatory urodynamics determines the tests ability to detect detrusor instability with an accurate symptom diary being the most important. INTRODUCTION Urodynamics describes a collection of tests designed to evaluate lower urinary tract function and identify dysfunc- tion. Urodynamics can be performed using retrograde ®ll- ing of the bladder within a room and is employed by most centres. The advantage of this method of infusion is that the ®lling rate is predetermined and the test can be completed within a short period of time. The disadvantage is that the test is performed using an unphysiological method of ®lling in an environment where the women may feel inhibited and may account for up to 15% sympto- matic women not having a urodynamic diagnosis 1 . Ambulatory urodynamic monitoring was developed to investigate lower urinary tract dysfunction under more physiological conditions. This test allows orthograde ®ll- ing of the bladder with urine while the subject is perform- ing daily activities 2 . Ambulatory urodynamics has been used to investigate symptomatic women in whom a diag- nosis had not been made following labouratory urody- namics. Many authors have reported greater sensitivity of ambulatory urodynamic monitoring in detecting abnormal detrusor contractions when compared with conventional urodynamics 2±6 . However, the prevalence of abnormal detrusor contractions in asymptomatic volunteers using ambulatory urodynamic monitoring can be up to 69% 7± 10 . These results call the validity of ambulatory urody- namic monitoring into question. Van Waalwijk van Doorn proposed an equation, the detrusor activity index 8,11 , to distinguish `abnormal' from `physiological' detrusor contractions. Some authors have attempted to automate their analysis and, most of them, to diagnose abnormal detrusor contractions without the patient being present during the analysis or referring to a urinary diary kept during ambulatory urodynamic monitoring. This may account for the high reported rate of abnormal detrusor contractions diagnosed on ambulatory urodynamic moni- toring. q RCOG 2001 British Journal of Obstetrics and Gynaecology PII: S0306-5456(00)00015-2 British Journal of Obstetrics and Gynaecology January 2001, Vol. 108, pp. 107±111 www.bjog-elsevier.com * Correspondence: Professor L. Cardozo, 8 Devonshire Place, London W1N 1PB, UK. a Department of Urogynaecology, King's College Hospital, London, UK b Department of Obstetrics and Gynaecology, Ospedale Multizonale, Varese, Italy