Neurourology and Urodynamics
Does Defective Volume Sensation Contribute to Detrusor Underactivity? 1
Phillip P. Smith,1* David J. Chalmers,2 and Richard S. Feinn3
Department of Surgery, University of Connecticut Health Center, Farmington, Connecticut 2 Department of Urology, Children’s Hospital Colorado, Aurora, Colorado 3 Quinnipiac University School of Medicine, North Haven Campus, North Haven, Connecticut Aims: The urodynamic finding of detrusor underactivity (DU) in neurologically intact unobstructed patients may relate to impaired volume sensations rather than detrusor contractile defects. We hypothesized that DU patients would demonstrate higher volumes but similar wall stress at sensation thresholds, and similar voiding contractility, compared to other groups. Methods: Chart review of urodynamic studies in neurologically normal, nonobstructed symptomatic patients. Urodynamic studies having the primary findings of DU, stress urinary incontinence (SUI), detrusor overactivity (DO), and increased sensations without detrusor overactivity (IS) were abstracted. Age, gender, and pressure/volume data associated with sensations and voiding parameters were collected. Wall stress at sensations was calculated. Urodynamic variables at standard sensations and progression across standard sensations were compared among the four groups. Results: Fifty-one urodynamic studies were analyzed for comparison. Mean age did not differ between groups. The DU group was predominantly male versus the other groups. DU, SUI, and DO had higher volume thresholds for strong desire than did IS. DU and DO demonstrated higher wall stress at strong desire than did IS and SUI. Watts factor was not significantly different between groups, however, DU had a smaller voided volumes and a higher post-void residuals. Conclusion: Increased volume and wall stress at strong desire, and similar contractility but the smaller voided volumes and elevated PVRs in DU suggest that diminished central sensitivity to volume afferent activity contributes to DU in nonobstructed, non-neurogenic symptomatic patients. Neurourol. Urodynam. # 2014 Wiley Periodicals, Inc. Key words: detrusor underactivity; urodynamics
INTRODUCTION
METHODS
The urodynamic observation of detrusor underactivity (DU) and the related clinical disorder of detrusor hyperreflexia with impaired contractility (DHIC) are common contributors to urinary incontinence, voiding disorders, and overactive bladder symptoms especially in the aged.1–3 While DU can be due to chronic obstructive or neurologic damage, in many cases the etiology is unknown. The nominally implied detrusor motor dysfunction is generally attributed to either impaired parasympathetic outflow or structural changes of the detrusor muscle resulting in diminished muscular contractile capabilities.2 However, animal and human evidence is not conclusive regarding a primary age-associated loss of detrusor contractile capabilities.4–12 We have previously reviewed the potential for sensory dysfunction as an etiologic component of DU and DHIC.13 Urine storage and voiding are dependent upon ongoing afferent feedback from the bladder and urethra during voiding.14,15 We therefore hypothesized that the observation of DU, with or without detrusor overactivity, as a primary urodynamic finding would be associated with higher volume sensory thresholds when compared to other common nonobstructive, non-neurologic urodynamic conditions. Since DU is often associated with aging, first and strong desires to void may be particularly affected based upon previously reported age-associated threshold changes16 Voiding detrusor strength can be assessed and compared via standard calculations such as the Watts Factor (WF).17 To test our hypothesis we compared urodynamic findings between groups having no known neurologic or obstructive cause for symptoms and findings.
With IRB permission, urodynamic records from 1 year in our laboratory were retrospectively reviewed and abstracted. Videourodynamic studies were conducted in conformance with the standards recommended by the International Continence Society except where specifically noted.18,19 Testing was performed with the patient in sitting position, using a filling rate of 50 ml/min of room temperature CystoConray II, with transducers zeroed to atmosphere at the level of the pubic symphysis. All urodynamics were conducted interactively with the urodynamicist and included bladder filling and at least an attempted voiding pressure/flow study. At the conclusion of each urodynamic examination, a written review of findings and an interpretive report was prepared by the supervising urodynamicist (PPS); the electronic urodynamics files including these reports were the documents reviewed for this study. Sensations were recorded at responses to standard questions: First Sensation (FS): ‘‘when you can first sense something in your bladder; that may or may not be a desire to empty.’’ First Desire (FD): ‘‘when you have the first thought of a desire to empty your bladder.’’ Strong Desire (SD): ‘‘when you would
#
2014 Wiley Periodicals, Inc.
Roger Dmochowski led the peer-review process as the Associate Editor responsible for the paper. Potential conflicts of interest: Nothing to disclose. Correspondence to: Phillip P. Smith, M.D., Department of Surgery, University of Connecticut Health Center, 263 Farmington Ave, Farmington, CT 06030. E-mail: [email protected] Received 25 February 2014; Accepted 12 June 2014 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22653
2
Smith et al.
interrupt a good conversation, meal, or show to go empty your bladder. Capacity (Cap): ‘‘when you are on the verge of losing control of your bladder or you begin to find this uncomfortable.’’ Four groups were selected for comparison based on the principle urodynamic impression reported. Patients with nonobstructive impairment of efficient voiding, either by elevated post-void residual, low voiding detrusor pressure in the absence of high flow, and/or poorly sustained detrusor contraction were considered to have DU. Patients unable to generate a detrusor contraction for voiding were not included in DU. The observation of early volume sensations (low volume sensory thresholds) in the absence of DO was grouped as Increased Sensations (IS) regardless of the presence/absence of other specific symptoms. Patients with detrusor overactivity but otherwise normal voiding were grouped as DO. Patients were grouped as stress incontinence (SUI) if leakage in response to increased intraabdominal pressure in the absence of detrusor contraction was the only abnormality of bladder filling and voiding. Excluded from this study were patients having reported neurologic/cognitive impairment, findings consistent with structural abnormality, inability to void and dysfunctional voiding, and studies in which a primary urodynamic condition among multiple observations could not be determined. €fer Urodynamic studies from men with voids plotting into Scha Zone 2 or greater on the eponymous nomogram and women with diminished flow (19 cm.w) especially with a history of anterior vaginal/peri-urethral surgery, were regarded as obstructive and also excluded. Data from each urodynamic record abstracted into a spreadsheet, included age, gender, volume and pressures at each sensation, voiding volumes and flow rates, and maximum Watts Factor (WFmax) as calculated over the voiding phase by the urodynamic software. Wall stress at each sensation was calculated as the product of detrusor pressure and volume, an approximation which correlates well with bladder afferent activity.15 Statistical Analysis
A one-way ANOVA was used to compare the four groups on mean age and a Chi-square was used to test for an association with gender. Prior to the analyses of the primary outcome variables, distributions were tested for normality and homogeneity of variance and when normality was rejected either a transformation or a nonparametric procedure was applied. The nonparametric Kruskal–Wallis test was used in place of ANOVA for the voiding outcomes, which violated normality. Volume, pressure, and wall stress all showed significant departure from normality and differing variation between groups. A natural log transformation on the three variables rectified these problems, permitting the use of the parametric mixed linear models analysis. In the mixed models, groups were coded as categorical variables and sensation progression (first sensation, first desire, strong desire, capacity) was either coded as continuous or categorical, depending on the trajectory of the outcome over sensation progression. An interaction between group and sensation progression was included in the models to test for differences in the trajectory of response between groups. RESULTS
Of 154 urodynamics examinations reviewed, 51 met criteria for inclusion. Table I presents demographic characteristics of the groups. The mean age for the entire sample was 62 years old Neurourology and Urodynamics DOI 10.1002/nau
TABLE I. Subject Characteristics DU (n ¼ 12) DO (n ¼ 12) Age Mean SD Gender Female Male
IS (n ¼ 6)
SUI (n ¼ 21) P-Value 0.087
67.9 14.2
56.9 22.0
50.7 12.0
65.1 12.6
3 (25%) 9 (75%)
8 (67%) 4 (33%)
6 (100%) 0 (0%)
20 (95%) 1 (5%)
Does Defective Volume Sensation Contribute to Detrusor Underactivity? 1
Phillip P. Smith,1* David J. Chalmers,2 and Richard S. Feinn3
Department of Surgery, University of Connecticut Health Center, Farmington, Connecticut 2 Department of Urology, Children’s Hospital Colorado, Aurora, Colorado 3 Quinnipiac University School of Medicine, North Haven Campus, North Haven, Connecticut Aims: The urodynamic finding of detrusor underactivity (DU) in neurologically intact unobstructed patients may relate to impaired volume sensations rather than detrusor contractile defects. We hypothesized that DU patients would demonstrate higher volumes but similar wall stress at sensation thresholds, and similar voiding contractility, compared to other groups. Methods: Chart review of urodynamic studies in neurologically normal, nonobstructed symptomatic patients. Urodynamic studies having the primary findings of DU, stress urinary incontinence (SUI), detrusor overactivity (DO), and increased sensations without detrusor overactivity (IS) were abstracted. Age, gender, and pressure/volume data associated with sensations and voiding parameters were collected. Wall stress at sensations was calculated. Urodynamic variables at standard sensations and progression across standard sensations were compared among the four groups. Results: Fifty-one urodynamic studies were analyzed for comparison. Mean age did not differ between groups. The DU group was predominantly male versus the other groups. DU, SUI, and DO had higher volume thresholds for strong desire than did IS. DU and DO demonstrated higher wall stress at strong desire than did IS and SUI. Watts factor was not significantly different between groups, however, DU had a smaller voided volumes and a higher post-void residuals. Conclusion: Increased volume and wall stress at strong desire, and similar contractility but the smaller voided volumes and elevated PVRs in DU suggest that diminished central sensitivity to volume afferent activity contributes to DU in nonobstructed, non-neurogenic symptomatic patients. Neurourol. Urodynam. # 2014 Wiley Periodicals, Inc. Key words: detrusor underactivity; urodynamics
INTRODUCTION
METHODS
The urodynamic observation of detrusor underactivity (DU) and the related clinical disorder of detrusor hyperreflexia with impaired contractility (DHIC) are common contributors to urinary incontinence, voiding disorders, and overactive bladder symptoms especially in the aged.1–3 While DU can be due to chronic obstructive or neurologic damage, in many cases the etiology is unknown. The nominally implied detrusor motor dysfunction is generally attributed to either impaired parasympathetic outflow or structural changes of the detrusor muscle resulting in diminished muscular contractile capabilities.2 However, animal and human evidence is not conclusive regarding a primary age-associated loss of detrusor contractile capabilities.4–12 We have previously reviewed the potential for sensory dysfunction as an etiologic component of DU and DHIC.13 Urine storage and voiding are dependent upon ongoing afferent feedback from the bladder and urethra during voiding.14,15 We therefore hypothesized that the observation of DU, with or without detrusor overactivity, as a primary urodynamic finding would be associated with higher volume sensory thresholds when compared to other common nonobstructive, non-neurologic urodynamic conditions. Since DU is often associated with aging, first and strong desires to void may be particularly affected based upon previously reported age-associated threshold changes16 Voiding detrusor strength can be assessed and compared via standard calculations such as the Watts Factor (WF).17 To test our hypothesis we compared urodynamic findings between groups having no known neurologic or obstructive cause for symptoms and findings.
With IRB permission, urodynamic records from 1 year in our laboratory were retrospectively reviewed and abstracted. Videourodynamic studies were conducted in conformance with the standards recommended by the International Continence Society except where specifically noted.18,19 Testing was performed with the patient in sitting position, using a filling rate of 50 ml/min of room temperature CystoConray II, with transducers zeroed to atmosphere at the level of the pubic symphysis. All urodynamics were conducted interactively with the urodynamicist and included bladder filling and at least an attempted voiding pressure/flow study. At the conclusion of each urodynamic examination, a written review of findings and an interpretive report was prepared by the supervising urodynamicist (PPS); the electronic urodynamics files including these reports were the documents reviewed for this study. Sensations were recorded at responses to standard questions: First Sensation (FS): ‘‘when you can first sense something in your bladder; that may or may not be a desire to empty.’’ First Desire (FD): ‘‘when you have the first thought of a desire to empty your bladder.’’ Strong Desire (SD): ‘‘when you would
#
2014 Wiley Periodicals, Inc.
Roger Dmochowski led the peer-review process as the Associate Editor responsible for the paper. Potential conflicts of interest: Nothing to disclose. Correspondence to: Phillip P. Smith, M.D., Department of Surgery, University of Connecticut Health Center, 263 Farmington Ave, Farmington, CT 06030. E-mail: [email protected] Received 25 February 2014; Accepted 12 June 2014 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/nau.22653
2
Smith et al.
interrupt a good conversation, meal, or show to go empty your bladder. Capacity (Cap): ‘‘when you are on the verge of losing control of your bladder or you begin to find this uncomfortable.’’ Four groups were selected for comparison based on the principle urodynamic impression reported. Patients with nonobstructive impairment of efficient voiding, either by elevated post-void residual, low voiding detrusor pressure in the absence of high flow, and/or poorly sustained detrusor contraction were considered to have DU. Patients unable to generate a detrusor contraction for voiding were not included in DU. The observation of early volume sensations (low volume sensory thresholds) in the absence of DO was grouped as Increased Sensations (IS) regardless of the presence/absence of other specific symptoms. Patients with detrusor overactivity but otherwise normal voiding were grouped as DO. Patients were grouped as stress incontinence (SUI) if leakage in response to increased intraabdominal pressure in the absence of detrusor contraction was the only abnormality of bladder filling and voiding. Excluded from this study were patients having reported neurologic/cognitive impairment, findings consistent with structural abnormality, inability to void and dysfunctional voiding, and studies in which a primary urodynamic condition among multiple observations could not be determined. €fer Urodynamic studies from men with voids plotting into Scha Zone 2 or greater on the eponymous nomogram and women with diminished flow (19 cm.w) especially with a history of anterior vaginal/peri-urethral surgery, were regarded as obstructive and also excluded. Data from each urodynamic record abstracted into a spreadsheet, included age, gender, volume and pressures at each sensation, voiding volumes and flow rates, and maximum Watts Factor (WFmax) as calculated over the voiding phase by the urodynamic software. Wall stress at each sensation was calculated as the product of detrusor pressure and volume, an approximation which correlates well with bladder afferent activity.15 Statistical Analysis
A one-way ANOVA was used to compare the four groups on mean age and a Chi-square was used to test for an association with gender. Prior to the analyses of the primary outcome variables, distributions were tested for normality and homogeneity of variance and when normality was rejected either a transformation or a nonparametric procedure was applied. The nonparametric Kruskal–Wallis test was used in place of ANOVA for the voiding outcomes, which violated normality. Volume, pressure, and wall stress all showed significant departure from normality and differing variation between groups. A natural log transformation on the three variables rectified these problems, permitting the use of the parametric mixed linear models analysis. In the mixed models, groups were coded as categorical variables and sensation progression (first sensation, first desire, strong desire, capacity) was either coded as continuous or categorical, depending on the trajectory of the outcome over sensation progression. An interaction between group and sensation progression was included in the models to test for differences in the trajectory of response between groups. RESULTS
Of 154 urodynamics examinations reviewed, 51 met criteria for inclusion. Table I presents demographic characteristics of the groups. The mean age for the entire sample was 62 years old Neurourology and Urodynamics DOI 10.1002/nau
TABLE I. Subject Characteristics DU (n ¼ 12) DO (n ¼ 12) Age Mean SD Gender Female Male
IS (n ¼ 6)
SUI (n ¼ 21) P-Value 0.087
67.9 14.2
56.9 22.0
50.7 12.0
65.1 12.6
3 (25%) 9 (75%)
8 (67%) 4 (33%)
6 (100%) 0 (0%)
20 (95%) 1 (5%)
