Estimation of the maximum contraction velocity of the urinary bladder from pressure and flow throughout micturition

De Novo Detrusor Underactivity and Other Urodynamic Findings after Radical Prostatectomy: A Systematic Review

Background and objectives: The aim of this systematic review is to evaluate the impact of radical prostatectomy (RP) on bladder function, with special attention towards detrusor underactivity investigated with the means of urodynamic evaluation. Materials and Methods: The review was performed in accordance with the PRISMA statement and was registered in the PROSPERO (ID#: CRD42020223480). The studied population was limited to men with prostate cancer who underwent urodynamic study prior to and after radical prostatectomy. Eight hundred twenty-seven studies were screened, with twenty-five finally included. A qualitative analysis was performed. Rates of detrusor underactivity (DU) before surgery were reported in eight studies and ranged from 1.6% to 75% (median of 40.8%). DU occurred de novo after RP in 9.1% to 37% of patients (median of 29.1%). On the other hand, preexisting DU resolved in 7% to 35.5% of affected men. Detrusor overactivity (DO) was the most frequently reported outcome, being assessed in 23 studies. The rate of DO preoperatively was from 5% to 76% (median of 25%). De novo was reported in 2.3–54.4% of patients (median of 15%) and resolved after RP in 19.6% to 87.5% (median of 33%) of affected patients. Baseline rates of bladder outlet obstruction (BOO) varied between studies from 19% to 59.3%, with a median of 27.8%. The most pronounced change after surgery was the resolution of BOO in 88% to 93.8% (median of 92%) of affected patients. Results: Rates of de novo impaired bladder compliance (IBC) varied from 3.2% to 41.3% (median of 13.3%), whereas the resolution of IBC was reported with rates ranging from 0% to 47% (median of 4.8%). Conclusions: BOO, DO, and DU are frequently diagnosed in men scheduled for RP. BOO is improved after RP in most patients; however, there is still a substantial rate of patients with de novo DU as well as DO which may impair functional outcomes and quality of life.

Urodynamics for postprostatectomy incontinence: when are they helpful and how do we use them?

Urodynamics is indicated for the evaluation of postprostatectomy incontinence unless an artificial urinary sphincter placement is the preferred option, as in cases of severe incontinence, prior radiation, or previous male sling or artificial urinary sphincter placement--when male sling is unlikely to achieve efficacy. Urodynamics should be performed only when there is a question it can answer that would affect treatment choice or outcome. Urodynamic findings of detrusor underactivity, overactivity, and reduced compliance are important considerations in deciding how best to treat postprostatectomy incontinence.

Detrusor contraction duration and strength in the patients with benign prostatic enlargement

OBJECTIVE

examine detrusor contraction duration (DCD) in relation with obstruction grade and strength of detrusor contractility; analyze individual correlations of this parameter with urodynamic, physiological and symptoms variables in patients with benign prostatic enlargement (BPE).

SAMPLE AND METHODOLOGY

102 patients with proved BPE, underwent complete urodynamic measurements (UDM), namely uroflowmetry, cystometry and pressure/flow studies. Postvoid residual urine (PVR) was measured and the International Prostate Symptom Score (I-PSS) was fulfilled by each patient. Methodology of measurement and definitions of UDM are based on definitions and terminology defined by the International Continence Society.

RESULTS

After grouping the patients (average age 64,7+/-8,5) related to obstruction grades according to the Schafer nomogram, ANOVA has shown a group extension of the detrusor contraction duration related to higher levels of obstruction (LinPURR 0-VI; p<0,01), which is also followed by stronger detrusor contractility (Pdetmax; p<0,001). Dichotomizing of the patients with DCD cut off point 90 sec. has shown that 67% patients with underactive detrusor have DCD>90 sec, while extension of DCD and increase of the obstruction level are directly related to preserved detrusor contractility only in 20,5% cases. There is neither statistically significant difference of DCD in the patients that are not in obstruction allocated in two groups depending on detrusor contraction strength, (t=1.2, p>0.05); nor in the patients who are in obstruction range, divided on the same way (t=0.568, p>0.05). There is also no difference of the same patients groups regarding PVR (t=1.38 and t=1.17, p>0.05). Individual correlation of DCD with I-PSS has not been shown (r=0.16, p>0.05), although there is a statistically significant correlation with its obstructive subset (r=0.20, p<0.05), as well as, with LinPUR and URA nomograms (r=0.33, r=0.29; respectively, p<0.005) and with Pdetmax (r=0.26, p<0.01), PdetQmax (r=0.24, p<0.05), Qmax and Qaver (r=0.31, p<0.005). DCD does not have individual correlations with patients' age, prostate volume and with cystometric capacity.

CONCLUSION

DCD is rather independent urodynamical variable, which does not correlate with I-PSS. Generally, DCD is prolonged during obstruction, while extension of DCD only partially depends on detrusor contraction strength. Practically, individual correlations of DCD with the urodynamic factors, which characterize obstructions, are modest.

A computer model of the neural control of the lower urinary tract

Better understanding of the underlying working mechanism of the neural control of the lower urinary tract will facilitate the treatment of dysfunction with a neurogenic cause. We developed a computer model to study the effect of a neural control system on lower urinary tract behavior. To model the mechanical properties and neural control, assumptions had to be made. These assumptions were based, as much as possible, on knowledge and hypotheses taken from the literature. With valid assumptions, it should be possible to simulate normal as well as pathological behavior. To test the computer model, first, normal behavior of the lower urinary tract was simulated, and secondly, the known features of bladder outlet obstruction were simulated after the properties of the urethra were changed. The simulation results are comparable with measured data, so the assumptions on which the model is based could be valid. If the assumptions are valid, the feedback loops used in the model are also important feedback loops in vivo, and the model can be used to gain insight into the underlying mechanism of neural control.

Mechanics and Ca(2+)-sensitivity of human detrusor muscle bundles studied in vitro

Mechanical properties of isolated smooth muscle strips from human urinary bladder were investigated in vitro. Bladder tissue was obtained from tumour-free wall regions of bladders from male patients undergoing cystectomy for bladder carcinoma. In intact muscle strips, activated with high-K+ solution, half-maximal force occurred at about 0.9 mM extracellular [Ca2+]. The length-active force relation was determined and the muscle strips were fixed for light and electron microscopy at optimal length for active force (1o). The maximal active force per unit smooth muscle cross-sectional area was 208 +/- 49 mN/mm2, n = 6. Chemically skinned preparations were obtained by treatment with triton X-100. These preparations had a steep [Ca2+]-force relation in the micromolar range which was influenced by calmodulin. The skinned preparations could be maximally activated by irreversible thiophosphorylation of the regulatory light chains. The force-velocity relation was determined in the maximally activated skinned muscle at 22 degrees C at 0.51o. When the muscle was shortened by 10%, force was reduced by 35% whereas the maximal shortening velocity was little affected.