Hypothesis / aims of study
Underactive bladder (UAB) is a symptom complex, of lower urinary tract symptoms. It may present as straining to void, hesitancy, poor, prolonged slow flow, incomplete emptying along with storage symptoms . This presentation can be due to low Detrusor pressure generated during voiding and can be in combination with bladder outflow obstruction, Detrusor overactivity with impaired contractility.
Bladder contractility index is derived from the formula, pDet@Qmax+5(Qmax).The individual parameters of pDet at Qmax , Qmax and PVR,contributes to the urodynamics diagnosis of Detrusor Underactivity.
The aim of this study is to identify the Urodynamic factor, to diagnose genuine Detrusor underactivity in Women in order to give a prognostic factor in the clinical outcome and management .
Study design, materials and methods
The Retrospective study of Urodynamics traces was done in 116 women. This study is in women with symptoms of Underactive Bladder. Patients with bothersome lower urinay tract symptoms and mixed urinary incontinence, with normal Urodynamics study was used as Control.
Bladder outflow obstruction with Detrusor Underactivity and genuine Detrusor Underactivity were included. Exclusion criteria were patients with bladder outflow obstruction only , Detrusor overactivity with impaired contractility.
Urodynamics parameters included were pDet@Qmax, Maximum flow rate Qmax ml/sec and postvoid residual volume in mls(PVR).Urodynamic values of Detrusor pressure at maximum flow pDet@Qmax and max flow ml/ sec (Qmax) is used to derive the Bladder contractility Index BCI, with the formula, pDet@Qmax+5(Qmax).
The average maximum Detrusor pressure at maximum flow is 11.9 cmsH2O in genuine detrusor Underactivity, average Maximum flow rate is 6.97 ml/ sec and average Post void residual is 485.7 mls.
In Detrusor Underactivity with Bladder Outflow Obstruction group, pDet@Qmax is 32.3 cmsH2O, maximum flow rate Qmax 7.99 ml/ sec and postvoid residual volume (PVR) is 303.6 mls.
The mean maximum Detrusor pressure at maximum flow in genuine Detrusor Underactivity, Detrusor underactivity with Bladder outflow obstruction and in normal urodynamics groups were 11.8 +12, 32.3 +16.9, 28 +12.1 respectively. The mean differences were statistically significant p =0.0001. The mean maximum flow rate in genuine Detrusor Underactivity, Detrusor underactivity with bladder outflow obstruction and in normal urodynamics were 6.9 + 7.1, 7.9 + 6.2, 23.1 +9.7 respectively which was statistically significant (p=0.0001). Similarly Post void residual volume in genuine detrusor underactivity, detrusor underactivity with bladder outflow obstruction and in normal urodynamics were 485.7 + 453.3, 303.5 + 316.7, 40.9 + 62.1 also statistically significant (p=0.0001). When we did a Post hoc analysis using LSD, there exists a significant difference (p=0.0001) between genuine Detrusor under activity and detrusor underactivity with bladder outflow obstruction (p=0.0001). Whereas the difference between detrusor underactivity with bladder outflow obstruction and normal urodynamics group was not statistically significant (p=0.152).
Interpretation of results
The pDet at Qmax is the deciding parameter in comparison to Qmax and PVR , to diagnose genuine DUA and BOO with DUA. There is statistical difference in pDet@Qmax in both the groups but not significant with Max flow rate and PVR.
Previous study showed a Bladder contractility Index cut off value of 113.4 with a statistical significance AUROC 67%, p=0.001 with sensitivity 73% and specificity 57% , to make a Urodynamic diagnosis of Detrusor Under-activity.
The current study further emphasises on the max detrusor pressure at peak flow , to be an important Urodynamic parameter in diagnosing Detrusor Underactivity .
All Continuous variables were represented as mean + SD. Other categorical variables were represented as %. Data entry was done in MS Excel Sheet. Data validation and analysis was carried out in SPSS version 25.0. We did ANOVA and Post Hoc Analysis using LSD (Least significant test) for comparing the different groups. All ‘p’ values <0.05 was considered as statistically significant.
Using ROC, we derived a cut off value for pDet@Qmax for genuine Detrusor Underactivity with normal as Control, in women to be </=12.5 cmsH20 with a sensitivity of 95% and specificity of 61%.