Association between Hyposensitivity of C-fiber Afferents at The Proximal Urethra and Storage/voiding Dysfunction in Female Patients with Detrusor Overactivity.

PURPOSE: We examined the associations between urethral sensation and storage/voiding function in female patients with detrusor overactivity (DO) by measuring urethral current perception threshold (CPT). MATERIALS AND METHODS: We retrospectively investigated the medical records of 27 consecutive patients with lower urinary tract symptoms who underwent cystometry, uroflowmetry (UFM), and urethral CPT tests from 2000 to 2015. Patients were classified into 2 groups: with/without DO. Seven DO-negative cases were selected as normal controls on cystometrogram (CMG) matching the inclusion criteria: bladder compliance ?12.5 mL/cmH2O, volume <275 mL at first sensation, and no comorbidities possibly influencing micturition. Finally, 17 patients were included. Urethral CPT was evaluated with intraurethral square-wave impulses at 3 Hz to stimulate C-fibers. Urethral loss coefficient (LC), reflecting urethral resistance during voiding, was calculated by curve-fitting a mathematical model to a UFM waveform. RESULTS: Urge incontinence (UI) was observed in 7 DO-positive patients, but not in those with normal CMG. Urethral CPT and LC were significantly higher in patients with DO than in those with normal CMG. Median urethral CPT significantly increased in patients with both DO and UI than in those without these symptoms (p<0.005). CPT values were correlated with the volume at first sensation (?=0.53, p<0.05) and LC (?=0.59, p<0.05). LC was not calculated in 3 cases due to poor curve-fitting. CONCLUSIONS: In females, urethral C-fiber afferents may become hyposensitive as the detrusor becomes overactive with UI in the storage phase. During voiding, C-fiber hyposensitivity may relate to increased functional resistance of the urethra to urine outflow.

Study on the relation of the shape of the uroflowmetrogram and the urethral loss coefficient calculated from the uroflowmetrogram.

The shape of the uroflowmetrogram reflects voiding conditions. Using a voiding simulation, we examined whether the urethral loss coefficient (LC) calculated from the approximated uroflowmetrogram correlates with parameters that regulate the shape of the uroflowmetrogram. A total of 161 normal and abnormal uroflowmetrograms were used. Normal female subjects and patients before and after transurethral resection of the prostate (TURP) were also studied. The ratio of maximum flow rate (Q(max)) to flow time (T), a parameter expressing the shape of the uroflowmetrogram, was calculated. The uroflowmetrograms were approximated using a voiding model, and the urethral LC was calculated. As a result, a strong negative correlation was observed between the Q(max)-flow time ratio, Q(max)/ T, and LC. Q(max)/T is the vertical to horizontal ratio of the uroflowmetrogram and indicates the average degree of acceleration of flow rate during voiding. On the other hand, urethral LC, which can be estimated from the shape of the uroflowmetrogram, is considered a kind of urethral resistance. We concluded that when urethral resistance is high, the degree of acceleration of flow rate is low on average. Our study also indicated that Qmax/T was less affected by voided volume (VV) compared to Q(max). As Q(max)/T is not as dependent on VV, it is useful for comparing cases with different VV.

Non-invasive estimation of intraurethral pressure profile from uroflowmetric curve.

BACKGROUND: An intraurethral pressure-time profile as urodynamic information was obtained in a non-invasive manner using an equivalent equation as a voiding model. METHODS: The reasonability of the voiding model was confirmed by applying it to an experimental flow curve likened to urinary flow. The flow curve was approximated and the pressure profile was estimated. From the uroflowmetric curves obtained in a normal subject and a patient with bladder outlet obstruction, the respective intraurethral pressure profiles were estimated. RESULTS: The pressure profile estimated from the approximated flow curve was found consistent with the profile of the difference between the pressure actually measured at two different portions in the experimental system. CONCLUSION: Non-invasive estimation of intraurethral pressure profile from uroflowmetric curves may be very useful to grasp intraurethral urodynamic information in clinical practice.