The influence of changes in extracellular and intracellular sodium concentration on detrusor contractility

OBJECTIVE: To determine the role of Na+-Ca2+ exchange in the regulation of isolated detrusor smooth muscle contractility. MATERIALS AND METHODS: Isolated guinea-pig detrusor strips were used to record isometric tension generated by; (a) electrical-field stimulation to elicit nerve-mediated responses; and (b) adding carbachol or superfusing with a high-K+ solution. The [Na+] gradient between extracellular and intracellular compartments was altered by: (i) reducing superfusate [Na+] in stages from 140.2 to 10.2 mm; (ii) addition of the cardiac glycoside strophanthidin (200 microm). RESULTS Reducing extracellular [Na+] reversibly reduced the magnitude of nerve-mediated contractions but increased the resting tension and magnitude of carbachol-induced contracture. The mean (sd) [Na+] required for a half-maximum effect on attenuating contractions, at 85.9 (6.2) mm, and developing contracture, at 59.1 (14.3) mm, were significantly different. The time constants of changes to nerve-mediated contractions and carbachol contracture were also significantly different, at 147 (5) vs 1207 (386) s, respectively. These differences suggest that separate mechanisms influence nerve-mediated contraction and contracture in low-Na+ solutions. Exposure to the cardiac glycoside strophanthidin produced a similar effect to low-Na+ solutions for carbachol contracture. Low-Na+ solutions had no significant effect on contractures induced by high extracellular [K+]. CONCLUSION Reducing the transmembrane [Na+] difference increases intracellular [Ca2+]. This increase is largely accommodated in intracellular stores, that can be released by exogenous carbachol. The results are consistent with the presence of a functional Na+-Ca2+ exchanger in the surface membrane. The lack of effect of low-Na+ solutions on contractures evoked by membrane depolarization is consistent with this conclusion. The reduction of the nerve-mediated contraction by low-Na+ solution might result from blockade of the nerve action potential.     

Changes in detrusor contractility after incontinence surgery

To study the effects of incontinence surgery on detrusor contractility, a group of 24 women who preoperatively voided without a detrusor contraction during voiding urethrocystometry were re-evaluated for detrusor contractility three months after surgery for stress urinary incontinence. Twelve women regained detrusor contractility during voiding and were able to resume spontaneous voiding after incontinence surgery. The remaining 12 patients, representing true detrusor atony, continued to void without a detrusor contraction, and the majority (10/12) needed prolonged postoperative bladder drainage prior to resumption of spontaneous voiding. Presence of reduced flow rates and absence of detrusor contraction during preoperative voiding indicated true detrusor hypotonicity. Two thirds of the patients voiding with normal flow rates but without a detrusor contraction during preoperative voiding regained detrusor contraction after incontinence surgery (p less than 0.05).     

Urge incontinence and impaired detrusor contractility in the elderly

Among the elderly, both urge incontinence and elevated residual urine are common. When they occur together, they present a challenging clinical problem, called detrusor hyperactivity with impaired contractile function (DHIC). Impaired detrusor contractility has two aspects: elevated post-void residual urine volume and reduced detrusor contraction strength. Geriatric urge incontinence, especially in combination with reduced bladder sensation, is associated with specific cortical abnormalities: frontal and global cortical underperfusion and cognitive impairment. We have investigated, in 73 elderly incontinent patients, whether either aspect of impaired contractility is associated with urge incontinence, reduced sensation or these cortical abnormalities. For post-void residual urine, there are no significant associations. Detrusor contraction strength, however, is significantly increased (not impaired) if there is urge incontinence, reduced bladder sensation, or cortical underperfusion. Thus, DHIC appears to be a coincidental occurrence of two common conditions with different etiological factors.     

Urodynamic aspects of detrusor mechanics and contractility

Summary The mechanical properties of detrusor muscle remain difficult to define. In vitro assessment may not represent accurately the behaviour of the in vivo organ, particularly as the bladder muscle must be regarded as a syncytium of inter-connecting fibres running in all directions. Detrusor mechanics have been described according to basic physical principles and according to intravesical pressure recorded during isometric detrusor contractions with the bladder outlet closed. This data, taken with measurements obtained during voiding, has led to the concept of the detrusor as a limited energy source. This concept challenges previously accepted views on the effect of outlet obstruction on detrusor function.     

Bladder contractility and idiopathic detrusor instability in males

Thirty males (mean age 54 ± 13 years) with an “idiopathic” delrusor instability and fully compensated bladders (no post-micturition residuals) were assessed urodynumically at a short distance of time (3 months, on average) from the beginning of clinical symptoms. Thirty age-matched controls were also investigated. Detrusor shortening velocity was found to be increased in the unstable patients (P < 0.001), which seemed to derive from enhanced contractile capability in the presence of normal urethral resistance. Such data confirm the results of previous investigations in males with obstructive detrusor instability as well as in women with idiopathic unstable bladders. The significance ol these findings was discussed. In particular, it was suggested that detrusor instability may involve changes leading both to more excitable bladder smooth muscle cells and to an easier electrical coupling between the same cells, thus, to enhanced contractile capability. It was also suggested that if an impaired contractile function in unstable bladders may be the final result of a process of detrusor collagenosis. increased bladder contractility would rather characteri/.e an initial phase in the natural history of detrusor instability. © 1994 Wiley-Liss, Inc.     

Stop-flow measurement of detrusor contractility in bladder outflow obstruction

Detrusor contractility was evaluated by measuring the increase in isometric pressure during a stop test in 25 men with benign prostatic hyperplasia. Before transurethral prostatic resection (TUR), a low pressure increase (delta P det iso) was associated with a large volume of residual urine. After TUR both the speed and the amplitude of isometric detrusor contractions during the stop test increased. A pre-operative low detrusor pressure increase was correlated with a great improvement in flow rate after TUR. The value of the stop-flow test was limited, however, since improvement in other urodynamic parameters could not be predicted.     

Characteristics of detrusor contractility during micturition in diabetics.

Pressure-flow studies were performed in 26 diabetics without bladder-outlet obstruction to objectively quantify detrusor activity and its variance during micturition by using the watts factor (WF) and to clarify the factors inducing a post-void residual volume (PVR). The WFmax values obtained from the pressure-flow studies were low in the majority of diabetics. There was a significant negative correlation between WFmax and PVR. A fading contraction strength during voiding was also observed that gave rise to an increased volume of residual urine, indicating that detrusor activity could not be maintained until the bladder was completely emptied in the diabetics. A positive correlation between bladder capacity and PVR was also observed. Our results indicate that residual urine in diabetics is related to a decrease in the maximum detrusor contraction strength, the fading of detrusor contractility during voiding, and an increase in the size of the bladder.     

前列腺增生症患者逼尿肌收缩力的定量判断与分级

为了对前列腺增生症（ＢＰＨ）患者逼尿肌收缩力进行定量判断与分级，作者选择１２０例年龄于５８～８９岁之间的ＢＰＨ患者，采用高级型尿动力测定仪进行压力－流率测定。测定结果由直线性被动尿道阻力关系（ＰＵＲＲ）及Ｓｃｈｆｅｒ列线图进行分析，将逼尿肌收缩力分为极弱（ＶＷ）、弱（Ｗ）、正常（Ｎ）及强（ＳＴ）四个等级。结果表明：１２０例ＢＰＨ患者中ＶＷ、Ｗ、Ｎ及ＳＴ级逼尿肌收缩力所占百分比各为１２．５％、２６．７％、４７．５％及１３．３％；高压－低流、高压－高流及正常或低压－低流等类型各占５５％、１．７％及４３．３％，并且逼尿肌损害经治疗及功能训练后收缩力级别可以增加。逼尿肌收缩力定量分级在ＢＰＨ患者的临床诊断、治疗方法选择、疗效评价及愈后等方面均具有重要的临床意义与应用价值，同时对其所依据的流体力学原理与尿动力学基础也进行了探讨。     

Effects of chronic cadmium exposure on contractility of the rat detrusor

. The chronic effects of Cd²⁺ on the myogenic contractions induced by acetylcholine (ACh), and the neurogenic contractions induced by electrical field stimulation (EFS) of the rat detrusor were investigated. Wistar Kyoto rats weighing 150–250 g were randomly divided into four groups each containing ten animals. Three groups received intraperitoneal Cd²⁺ (0.25, 0.5 and 1 mg/kg, respectively) dissolved in saline twice a week for 3 months. The control group received only saline (0.3 ml). At the end of 3 months, the urinary bladders were surgically removed and a strip of detrusor was prepared from each bladder. An atomic absorption device and the standard addition method were used to determine blood levels of Cd²⁺ and the Cd²⁺ levels of the remaining parts of each bladder. The responses of the detrusor strips were studied in organ chambers. The tissues were first treated with ACh and then with EFS. The responses were recorded by isotonic transducers. The tissue Cd²⁺ levels were significantly increased in the Cd²⁺ treated rats in a dose-dependent manner except in the 0.25 mg/kg Cd²⁺ treated group. ACh-induced contractions were significantly attenuated only in the 1 mg/kg Cd²⁺ treated rats. The contractions induced by EFS were significantly decreased in all of the Cd²⁺-treated groups, but there were no significant differences between the groups. This study showed that Cd²⁺ exposure for 3 months impairs neurogenic and myogenic contractile activity in the rat detrusor muscle. This action seems to be at least partly due to an inhibition of the cholinergic muscarinic system. This may have clinical implications for people who are exposed to Cd²⁺.     

Length dependence of the contractility of pig detrusor smooth muscle fibres

Evidence on the length dependence of the contraction velocity of smooth muscle fibres is contradictory. Nevertheless, a thorough understanding of this dependence is essential for a correct urodynamic diagnosis of voiding problems. We studied muscle fibres of pig urinary bladders (n=23). Force-velocity relations were measured at different muscle lengths with a stop test technique. This method involves measuring force generation of electrically stimulated muscle fibres during controlled shortening from a pre-shortening length at a pre-set velocity to a fixed stop-length. We normalized the length dependence of the measured properties to slack length, optimum length (the length at maximum isometric force generation), and passive force. Isometric force was found to be length dependent with an optimum length of 290 ± 68% of the slack length (n=11, P < 0.05). The maximum shortening velocity was 0.37 ± 0.14 s − 1 related to the slack length and 0.13 ± 0.05 s − 1 related to the optimum length and was not length dependent (n=16, P < 0.05). Slack length is preferable to normalize the length dependence of smooth muscle. Received: 8 August 2000 / Accepted: 6 December 2000     

投射逼尿肌等容收缩压1在评价女性逼尿肌收缩力中的应用

目的 探讨投射逼尿肌等容收缩压1(PIP1)在评价女性逼尿肌收缩力中的应用.方法 女性患者112例,平均年龄55(18～84)岁.其中腰椎间盘突出症58例.均行尿动力学检查,PIP1以公式P_(det) Q_(max)+Q_(max),计算.统计学分析PIP1与患者年龄、WF_(max)、膀胱初始感觉、膀胱最大容量的相关性.112例患者分为PIP1降低组(＜30 cm H_2O,1 cm H_2O=0.098 kPa)、正常组(30～75cm H_2O)和升高组(＞75 cm H_2O),58例腰椎间盘突出症患者分为术前、术后组,比较各组间的尿动力学参数.结果 112例患者平均PIP1为(42.6±16.3)cm H_2O,平均P_(det) Q_(max)(29.2±15.2)cm H_2O,平均Q_(max)(13.3±7.3)ml/s,平均WF_(max)(9.2±5.4)μW/mm~2.PIP1与年龄(r=0.343,P=0.000)、WF_(max)(r=0.540,P=0.000)之间有显著相关性.PIP1降低组、正常组、升高组之间年龄(P=0.006)、P_(det) Q_(max)(P=0.000)、Q_(max)(P=0.003)、WF_(max)(P=0.000)差异有统计学意义.58例腰椎间盘突出症患者术前、术后平均PIP1分别为(44.4±14.2)、(35.4±13.5)cm H_2O,平均P_(det) Q_(max)分别为(29.3±13.2)、(23.6±11.2)cm H_2O,平均Q_(max)分别为(15.1±7.7)、(11.8±5.9)ml/s,患者术后PIP1显著下降(P=0.027),组间P_(det) Q_(max)(P=0.114)和Q_(max)(P=0.122)差异无统计学意义.结论 PIP1适于评价女性逼尿肌收缩力,PIP1与年龄和WF_(max)有显著相关性.     

Voiding urgency and detrusor contractility in women with overactive bladders.

AIMS: To check whether the contractility of overactive bladders would be affected by voiding urgency. METHODS: We urodynamically studied 100 women: 20 normal controls (group 1), 60 patients with idiopathic detrusor overactivity (DO), and 20 with neurogenic DO from intracerebral lesions. The idiopathic DO groups 2A (n = 20), 2B (n = 20), and 3 (n = 20) had moderate, severe, and no voiding urgency, respectively. The neurogenic DO group 4 had severe urgency. The delay time of urgent void at cystometry (2 minutes or more or, respectively, less than 2 minutes) defined moderate or severe urgency. Detrusor contractility was defined by the maximum bladder external voiding power (WF(max)). RESULTS: WF(max) was higher in the idiopathic DO patients than in the controls, had the highest values in group 2B, and did not differ significantly between groups 1-4 and 2A-3. CONCLUSIONS: We inferred from our data that idiopathic DO suggests a facilitation of voiding contractions and that such facilitation might be centrally amplified by severe urgency. This amplifying effect would probably be impaired in cases of neurogenic DO from intracerebral lesions.     

Bladder outlet obstruction versus impaired detrusor contractility: the role of outflow

The uroflow curves of 45 men with either bladder outlet obstruction or impaired detrusor contractility were retrospectively reviewed. The definitive diagnoses were attained by clinical and video-urodynamic studies with simultaneous detrusor pressure and uroflow measurements. Eight parameters were analyzed to determine if uroflow can differentiate obstruction from impaired contractility. There were no differences between the 2 groups in any of the parameters. This finding suggests that uroflowmetry as a single examination cannot distinguish between bladder outlet obstruction and impaired detrusor contractility.     

前列腺增生症病人的逼尿肌收缩力减弱与剩余尿

应用压力流率测定技术，经Ｓｃｈ¨ａｆｅｒ列线图和直线被动尿道阻力关系（ＬｉｎＰＵＲＲ）定量分析９５例前列腺增生症病人的逼尿肌收缩强度。逼尿肌收缩强度分为四级：很弱（ＶＷ）、弱（Ｗ）、正常（Ｎ）和强（ＳＴ）。导管法结合压力流率测定时膀胱灌注量与排出量之差确定剩余尿。结果表明，逼尿肌收缩力很弱和弱与收缩力正常和强的病人之间存在显著性差异（Ｐ＜０．００１）。剩余尿量随逼尿肌收缩力减弱而增加。逼尿肌收缩力很弱的病人术后剩余尿量未改善；逼尿肌收缩力弱的病人术后逼尿肌收缩力可能改善，剩余尿减少；逼尿肌收缩力正常或强的病人术后剩余尿明显减少。     

全麻对膀胱逼尿肌功能的影响及其尿动力学的变化特点

目的 研究全麻对膀胱逼尿肌功能的影响及其尿动力学的变化特点. 方法 2010年11月至2011年10月,全麻手术患者42例,男28例,女14例.年龄18 ～ 70岁,平均38岁.腹腔镜手术35例,开放手术7例,于麻醉前、麻醉期、麻醉结束清醒后进行尿动力学检查,统计学比较麻醉前后尿动力学参数的差异.42例患者均成功完成检查.麻醉期间膀胱逼尿肌排尿功能丧失,充盈膀胱至麻醉前测得患者的最大膀胱容量后停止灌注.根据麻醉结束清醒后检查的参数将患者分为正常顺应性组27例和低顺应性组15例,对麻醉前后数据行统计学分析. 结果 正常顺应性组麻醉前初尿意容量(FD)、强烈尿意容量(SD)、膀胱最大容量(MCC)分别为(118.2±16.8)、(204.6±27.4)、(395.8±50.1)ml,麻醉后分别为(160.9 ±21.6)、(244.8±44.0)、(394.7±56.9) ml,FD、SD麻醉前后差异有统计学意义(P＜0.01),MCC无统计学意义(P＞0.05).低顺应性组麻醉前FD、SD、MCC分别为(118.9±15.1)、(208.8±22.9)、(403.9±48.1)ml,麻醉后分别为(123.0±16.9)、(189.1±35.9)、(275.4±33.7)ml,麻醉前后差异均有统计学意义(P＜0.01).低顺应性组患者予留置测压管1h后复测,膀胱顺应性均恢复正常. 结论 全麻结束后膀胱稳定性正常,感觉功能较正常状态减弱,患者逼尿肌均能有效收缩并自主排尿,部分患者出现一过性顺应性降低;正常情况下全麻患者可予麻醉诱导后留置尿管,术毕后及时拔除.