Morphometry of the obstructed detrusor: I. Review of the issues

Detrusor Overactivity May Be a Prognostic Factor for Better Response to Combination Therapy Over Monotherapy in Male Patients With Benign Prostatic Enlargement and Storage Lower Urinary Tract Symptoms

Purpose

Several trials have shown that in men with overactive bladder (OAB) and benign prostate enlargement (BPE), the combination of an α-blocker with an anticholinergic is superior to α-blocker monotherapy. The purpose of this study is to explore whether urodynamic detrusor overactivity (DO) affects clinical outcomes in men with BPE and OAB.

Methods

This is a post hoc analysis of a prospective, randomized trial, designed to evaluate the changes of morphometric parameters of the prostate following monotherapy or combination therapy in men with BPE-OAB. The initial study recruited men aged ≥50 years, with BPE and predominantly storage lower urinary tract symptoms (LUTS). Patients were randomized to receive tamsulosin monotherapy or a combination of tamsulosin and solifenacin for 26 weeks. All participants completed a 3-day bladder diary and the International Prostate Symptom Score (IPSS), and then underwent pressure-flow and ultrasonographic studies. Data were stratified and analysed based on the urodynamic observation of DO at baseline (DO vs. non-DO). The primary endpoint was the mean change in urgency episodes from baseline. Secondary outcomes were the changes in nocturia, total IPSS, and urodynamic parameters.

Results

Sixty-nine men were initially randomized, but only 60 men were included in this analysis. Urgency episodes significantly improved in men with DO who received combination therapy compared to the DO monotherapy subgroup (P=0.04) or to the non-DO combination treatment subgroup (P=0.038). Nocturia also improved in the DO combination treatment subgroup as compared to the non-DO combination subgroup (P=0.037). The 24-hour frequency and total IPSS significantly improved from baseline without significant differences among the subgroups.

Conclusions

The present study suggests that baseline DO could be a prognostic factor for a better response to combination therapy over monotherapy in men with BPE and storage LUTS.

Basic mechanisms of urgency: roles and benefits of pharmacotherapy

INTRODUCTION

Since urgency is key to the overactive bladder syndrome, we have reviewed the mechanisms underlying how bladder filling and urgency are sensed, what causes urgency and how this relates to medical therapy.

MATERIALS AND METHODS

Review of published literature.

RESULTS

As urgency can only be assessed in cognitively intact humans, mechanistic studies of urgency often rely on proxy or surrogate parameters, such as detrusor overactivity, but these may not necessarily be reliable. There is an increasing evidence base to suggest that the sensation of ‘urgency’ differs from the normal physiological urge to void upon bladder filling. While the relative roles of alterations in afferent processes, central nervous processing, efferent mechanisms and in intrinsic bladder smooth muscle function remain unclear, and not necessarily mutually exclusive, several lines of evidence support an important role for the latter.

CONCLUSIONS

A better understanding of urgency and its causes may help to develop more effective treatments for voiding dysfunction.

Null mutation in macrophage migration inhibitory factor prevents muscle cell loss and fibrosis in partial bladder outlet obstruction

Idiopathic detrusor underactivity (DU) and detrusor decompensation which develops following partial bladder outlet obstruction (pBOO) are both associated with smooth muscle degeneration and fibrosis. Macrophage migration inhibitory factor (MIF), an important mediator of bladder inflammation, has been shown to promote fibroblast survival and muscle death in other tissues. We evaluated the hypothesis that MIF has similar actions in the bladder by studying detrusor responses to pBOO or sham surgery in anesthetized female mice rendered null for the mif gene (MIF KO) and in wild-type (WT) controls, all killed 3 wk after surgery. WT mice revealed intense MIF immunoreactivity in urothelial cells which decreased, without change in overall mif mRNA levels. Stereologically sound quantitative morphometric measurements were performed in the middetrusor region of each bladder. MIF KO bladders were normal in appearance, yet were 30–40% heavier, with increased middetrusor collagen and muscle, compared with WT controls. In WT mice, pBOO increased the collagen-to-muscle ratio 1.9-fold and middetrusor collagen 1.8-fold, while nucleated muscle counts were 22% lower. In MIF KO mice, by contrast, pBOO had no significant effect on any of these parameters. In primary bladder muscle cultures, treatment with rMIF protein increased TUNEL staining, raising the proportion of early and late apoptotic cells on flow cytometry. Our studies implicate MIF in the sequence of events leading to detrusor muscle loss and fibrosis in obstruction. They raise the possibility that strategies designed to antagonize MIF synthesis, release, or biological activity could prevent or delay DU and urinary retention.

Smooth muscle membrane organization in the normal and dysfunctional human urinary bladder: a structural analysis

PURPOSE

The decline in contractile properties is a characteristic feature of the dysfunctional bladder as a result of infravesical outlet obstruction. During clinical progression of the disease, smooth muscle cells undergo structural modifications. Since adaptations to constant changes in length require a high degree of structural organization within the sarcolemma, we have investigated the expression of several proteins, which are involved in smooth muscle membrane organization, in specimens derived from normal and dysfunctional organs.

MATERIALS AND METHODS

Specimen from patients with urodynamically normal/equivocal (n = 4), obstructed (n = 2), and acontractile (n = 2) bladders were analyzed relative to their structural features and sarcolemmal protein profile.

RESULTS

Smooth muscle cells within the normal urinary bladder display a distinct sarcolemmal domain structure, characterized by firm actin-attachment sites, alternating with flexible "hinge" regions. In obstructed bladders, foci of cells displaying degenerative sarcolemmal changes alternate with areas of hypertrophic cells in which the membrane appears unaffected. In acontractile organs, the overall membrane structure remains intact, however annexin 6, a protein belonging to a family of Ca2+-dependent, "membrane-organizers," is downregulated.

CONCLUSION

Degenerative changes in smooth muscle cells, which are chronically working against high resistance, are preferentially located within the actin-attachment sites. In acontractile bladders, the downregulation of annexin 6 might have a bearing on the fine-tuning of the plasma membrane during contraction/relaxation cycles.

Physiology of incontinence

The physiology of incontinence is related to the normal physiologic mechanisms of aging and to abnormal pathologic changes that recently have become better understood. Further research is needed to develop new methods of pharmacologic treatment.

Overactive bladder and men: Indications for anticholinergics

Similar to bladder outlet obstruction (BOO), overactive bladder (OAB) symptoms are very common and increase in prevalence as men age. Whether or not OAB symptoms are thought to be secondary to BOO, the goal of treatment of symptoms should result in an improved quality of life and ultimately prevent clinical deterioration. A common dilemma when treating men with obstruction and OAB is the risk of acute urinary retention or morbidities related to increasing postvoid residuals. In this article, the relationship of OAB to BOO is examined and the role of urodynamics and data on the use of anticholinergics in men with OAB and obstruction are reviewed. An algorithm for managing men with OAB also is proposed. In men with OAB without evidence of obstruction (including OAB after treatment for BOO), first-line medical therapy with anticholinergics is indicated. However, in men with OAB and concomitant BOO, nomogram has been developed to assist in the management of patients at risk for urinary retention. Men with significant obstruction should be appropriately treated to decrease bladder outlet resistance before adding anticholinergics for the treatment of OAB.

Overactive bladder in men: special considerations for evaluation and management

Lower urinary tract symptoms (LUTS) in men may arise from a variety of underlying causes, including benign prostatic hyperplasia. LUTS may have a significant component of storage symptoms (urgency, frequency, urge incontinence) at presentation; however, the absence of overactive bladder (OAB) symptoms does not necessarily imply pure outlet obstruction nor does their presence indicate the lack thereof. Symptomatic correlates to urodynamic findings are high when considering isolated OAB symptoms. However, mixed presentations or more overtly obstructive scenarios have less correlation with baseline symptom appraisal instruments. The ideal approach for diagnosis and management is predicated on a graded approach, with more invasive evaluation withheld for those men in whom presumptive therapy fails or who present with associated complex symptoms and in whom a higher level of intervention is being considered. The increasing incidence of LUTS with age implies a partial detrusor contribution, which must be considered in the overall management schema.

Bladder wall thickness in normal adults and men with mild lower urinary tract symptoms and benign prostatic enlargement

There is evidence that increased bladder wall thickness can be a useful parameter in the evaluation of men with clinical benign prostatic hyperplasia (BPH). However, normal values for bladder wall thickness (BWT) in adults have not been established. BWT was measured by suprapubic ultrasonography. Bladder volume was calculated as the product of the ultrasonographic measurements of bladder height, width and depth, and a correction factor (0.6). Three groups were assessed: men with normal lower urinary tracts (n = 172; mean age, 39.9), women with normal lower urinary tracts (n = 166; mean age, 37.8), and men with mild lower urinary tract symptoms (LUTS) and clinical benign prostatic enlargement (BPE) (n = 150; mean age, 66.4). For the whole group of men and women with normal bladders, mean BWT was 3.35 mm, and BWT appeared normally distributed. There were a weak negative correlation with bladder volume (r = -0.12, P < 0.003) and a weak positive correlation for BWT and age for both men (r = 0.12, P < 0.014) and women (r = 0.17, P < 0.013). Mean BWT was 3.04 mm in healthy women, 3.33 mm in healthy men, and 3.67 mm in men with LUTS and BPE. Sub-dividing normal men into different age groups showed an increasing mean BWT of 3.08 mm (<20 years, n = 27), 3.25 mm (21-40 years, n = 75), 3.42 mm (41-60 years, n = 39), and 3.57 mm (>60 years, n = 31) for those sub-groups. BWT in normal adult women is 3.0 +/- 1 mm and 3.3 +/- 1. 1 mm in normal adult men. A small increase in BWT with age is seen for both genders, and BWT tends to be greater in men than in women. Men with LUTS and BPE show a moderate increase in BWT. Adjustments for bladder volume are for practical purposes negligible, although there is a small decrease in BWT with increasing volume.

Lower urinary tract symptoms, benign prostatic obstruction and the overactive bladder

Lower urinary tract symptoms (LUTS), benign prostatic obstruction (BPO), and the overactive bladder have increasing prevalence with age in both men and women (with the obvious exception). The question is, are they interrelated or independently related to age? The specific issue is whether BPO causes the overactive bladder. There are two pieces of evidence that might appear to suggest such a cause and effect. First, the overactive bladder is more common in men than in women of the same age, although physiologically, men are 5-10 years older at the same biological age. Second, the overactive bladder resolves in two-thirds of individuals after surgical interventions such as transurethral prostatectomy. The symptoms suggestive of an overactive bladder are the most troublesome, even though they may not be the most prevalent. Long-term follow-up studies with repeated urodynamic investigations have shown that the incidence of the overactive bladder and its attendant symptoms increases despite there being no deterioration in outlet obstruction over follow-up periods of 10 and 20 years. These data, and others, indicate that the situation is not as straightforward as some believe. The statement that 'the overactive bladder is secondary to BPO' cannot be made, as there are too many unanswered questions and pieces of the puzzle that do not fit. The overactive bladder is undoubtedly associated with BPO, and it leads to the most troublesome LUTS in older men. Epidemiological research, coupled with urodynamic evaluation, may provide further evidence. We also need better and more relevant models (e.g. ageing animals), together with further histological and other biological data before the waters become crystal clear.

Possible role of endothelin-1 in the rabbit urinary bladder hyperplasia secondary to partial bladder outlet obstruction

OBJECTIVES

Urinary bladder hypertrophy and hyperplasia are common features of bladder outlet obstruction (BOO). The urinary bladder is known to synthesize endothelin-1 (ET-1), which is a potent vasoconstrictor peptide with mitogenic properties. Using an animal model of partial BOO, we investigated the potential role of ET-1 and its receptor subtypes (ET(A) and ET(B)) in bladder smooth muscle cell (SMC) proliferation.

MATERIALS AND METHODS

Partial BOO was produced in adult male New Zealand White rabbits. After 3 weeks, the bladder was removed and SMCs from the dome and bladder neck were grown using standard explant methodology. At passage 2, the cells were made quiescent and then further incubated in foetal calf serum (FCS), control age-matched rabbit serum (CRS) or partial BOO serum (BRS) in the presence or absence of ET(A)-antagonist (BQ123) or ET(B)-antagonist (BQ788). SMC proliferation was then measured 24 h later with 5-bromo-2'deoxy-uracil and by cell counting using a haemocytometer at 48 h. Immunostaining for alpha-actin was performed on detrusor and bladder neck cells to confirm the presence of smooth muscle cells.

RESULTS

BQ123 and BQ788 did not influence detrusor or bladder neck SMC proliferation in FCS or CRS. However, in the presence of BRS, BQ123 and BQ788 (100 nmol/L) significantly (p = 0.008) inhibited detrusor and bladder neck SMC proliferation. Cell counts were significantly reduced from the detrusor (p = 0.03, p = 0.01 with BQ123 and BQ788, respectively) and bladder neck (p = 0.01 for both BQ123 and BQ78).

CONCLUSIONS

These results suggest that ET antagonists may have a role in preventing SMC hyperplasia associated with partial BOO.

Effect of partial outlet obstruction on the myogenic response to field stimulation

1. Experimental studies of outlet obstruction have been performed on rats, rabbits, guinea pigs, cats, dogs and pigs. There is evidence that partial outlet obstruction can alter the membrane properties of the bladder smooth muscle and result in progressive denervation. The current studies were designed to evaluate the effects of moderate partial outlet obstruction on the response of isolated strips of rabbit bladder smooth muscle to field stimulation in the absence and presence of tetrodotoxin (TTX). 2. The results are as follows: In the absence of TTX, partial outlet obstruction resulted in a significant reduction in the neurogenic response at all frequencies. In the presence of 1 microM TTX, which caused maximal inhibition of the release of neurotransmitters, partial outlet obstruction caused a significant increase in the myogenic response to field stimulation. 3. These studies clearly demonstrate that partial outlet obstruction results both in a significant decrease in the neurogenic response of the obstructed bladder to field stimulation and in a significant increase in the myogenic component.

Functional anatomy of the organs of micturition

The anatomy of the organs of micturition has been the subject of study for nearly 150 years. As a result of advances in techniques and methods of clinical and research investigation, studies over the past three decades have intensified and have been increasingly directed at the functional implications and significance of organ anatomy and structure. This has led to revision of many traditional ideas about micturition and the development of new viewpoints and modalities for study of its disorders. This article summarizes the evolution of our thinking and understanding of the functional anatomy of the bladder and urethra over the years, and suggests possible directions for continued clinical study and investigation.

Effect of slow and rapid cystometry on in vitro rat urinary bladder DNA synthesis

1. Partial outflow obstruction induces marked changes in detrusor contractile function and morphology. One common finding in all experimental animal models of partial outflow obstruction is a significant increase in bladder mass. 2. Previous studies have demonstrated that partial outlet obstruction induces a rapid and substantial increase in [3H]thymidine incorporation into virtually all cellular elements of the bladder. 3. The present study was designed to investigate the [3H]thymidine uptake and localization induced by exposure of the in vitro whole rat bladder model to various intravesical pressures and rates of intravesical infusion. 4. The results are as follows: (a) There were no differences in DNA concentration between control and other groups. (b) Slow infusion induced a mild increase in DNA synthesis ([3H]thymidine incorporation) at 0.5 ml and a significantly greater level of DNA synthesis at 1.6 ml. (c) [3H]thymidine incorporation was significantly increased by exposure to 7.5 cm H2O, 15 cm H2O, and 30 cm H2O. (d) Exposure to 60 cm H2O and 90 cm H2O did not initiate an increase in [3H]thymidine incorporation. (e) Autoradiography showed that all tissue elements (urothelium, connective tissue, smooth muscle) participated in the response.

Detrusor Morpho-functional Correlations in Obstruction due to Benign Prostatic Hyperplasia (BPH)

This study was aimed at checking out a possible connection between detrusor primary lesions and clinical and urodynamic data in patients with cervico-prostatic obstruction. 40 patients were evaluated, of whom 32 had symptomatic benign prostatic hyperplasia and 8 were controls. A biopsy of the right side wall of the bladder was carried out. The lesions found (muscular hypertropy, fibroelastosis, alteration of the nerve fibres) in relation to their gravity, correlated to the presumable date when symptoms started and to three data from urodynamic evaluation (significant residual p.m., degree of obstruction according to Schafer's chart, presence of detrusor-motor instability). The interference of physiological ageing on results is not underestimated, but this correlation exists. However, the lack of fine quantitative evaluations of follow-up on the possible reversibility of the same lesions after removal of the obstruction, make it impossible at this stage to state how close the correlation is.

3H-thymidine uptake by the rat urinary bladder after partial outflow obstruction

Partial outflow obstruction induces marked changes in detrusor contractile function and morphology. One common finding in all experimental animal models of outflow obstruction is a significant increase in bladder mass. It is not clear which tissue compartments undergo hypertrophy, hyperplasia, or both. The present study was designed to evaluate the time-related changes in 3H-thymidine uptake and distribution within each tissue compartment induced by partial outflow obstruction using autoradiography. Partial outlet obstruction in rats induced a mild 2-fold increase in mass over a 14 day period. DNA synthesis increased significantly at 1 day following surgery, and remained increased through 7 days. DNA synthesis returned to control levels by 14 days. Distribution studies (using autoradiography) demonstrated a marked increase in the number of labelled urothelium cells at 1 and 3 days after obstruction. Sham surgery also initiated an increase in the number of labelled cells in the urothelium at 1 day. Although both sham and obstructive surgeries induced substantial increases in the labelling of cells within the connective tissue components, the magnitude of the increase in labelled connective tissue cells of the obstructed bladders was greater than that of the sham group. The number of labelled smooth muscle cells of the obstructed bladder increased significantly at 3, 5, and 7 days. However, there were no changes in smooth muscle incorporation of 3H-thymidine by the sham groups. In conclusion, partial outflow obstruction induced time-dependent increases in bladder wall proliferation. The urothelium and connective tissue were the compartments first affected, followed by smooth muscle.

Structural basis of geriatric voiding dysfunction. IV. Bladder outlet obstruction

Several aspects of the pathogenesis of voiding dysfunction in bladder outlet obstruction remain unresolved. The structural basis of obstructive versus nonobstructive dysfunction was investigated in a prospective ultrastructural/urodynamic study of 35 elderly subjects of comparable age. Detrusor structure was examined by electron microscopy, with blinded clinical and urodynamic information. Seven detrusor specimens were segregated by a distinctive myohypertrophy, structural pattern, which matched with 6 male and 1 female subjects 72 to 96 years old (mean age 83) who had urodynamically proved outlet obstruction. This pattern was characterized by widely separated muscle cells with reduction of intermediate cell junctions, collagenosis, that is abundant collagen plus some elastic fibers, in the markedly widened spaces between individual muscle cells and abundant profiles characteristic of enlarged, hypertrophic muscle cells. Superimposed degeneration of muscle cells and axons in 6 specimens matched those of 5 men and 1 woman who had impaired detrusor contractility. In 3 specimens there were also abundant protrusion junctions and ultra-close abutments; these matched those of 2 men and 1 woman with obstruction plus detrusor overactivity. Observations on the degree of bladder trabeculation in the entire population of 35 subjects are presented. It is concluded that bladder outlet obstruction is associated with changes in detrusor structure that can account for the resultant voiding dysfunction. Features of the myohypertrophy pattern, with or without superimposed degeneration, can explain overall weakness of the obstructed detrusor despite hypertrophy of its cells. Protrusion junctions and abutments probably mediate electrical coupling of muscle cells leading to involuntary contractions in the overactive (unstable) obstructed detrusor. Excessive deposits of elastic fibers (hyperelastosis) between widely separated muscle cells and in interstitium are suggested as the probable structural basis for increased bladder distensibility and chronic retention.

Structural basis of geriatric voiding dysfunction. III. Detrusor overactivity

Detrusor overactivity in the absence of outlet obstruction is common in the elderly. The few available studies on structure of the overactive detrusor generally have dealt only with its innervation. We conducted a prospective study to examine the ultrastructure of muscle cells, interstitium and nerves of the detrusor in biopsies from 35 elderly subjects to identify structural correlates of various urodynamically defined forms of voiding dysfunction. A distinctive dysjunction structural pattern was identified blindly in 15 detrusor biopsies. These patterns matched 12 women and 3 men 66 to 96 years old (mean age 79 years) who were segregated independently as a detrusor overactivity group by prospective urodynamic evaluation. All but 1 patient had incontinence and/or other symptoms, and none had diabetes or a significant neurological deficit. The dysjunction pattern was characterized by moderately widened intercellular spaces, scarce intermediate muscle cell junctions, abundant distinctive protrusion junctions and ultra-close cell abutments, and absence of profiles characteristic of enlarged hypertrophic cells. There was superimposed widespread degeneration of muscle cells and axons in 8 specimens, which matched the subgroup of patients with impaired detrusor contractility. The remaining 7 specimens with no degeneration matched the patients with normal contractility. Protrusion junctions and abutments are proposed as a possible manifestation of a process of muscle cell de-differentiation associated with natural aging, as well as the mediator in overactive detrusor of electrical coupling of muscle cells, in lieu of their normal mechanical coupling curtailed by marked reduction of intermediate cell junctions. On this basis, a bipartite myogenic mechanism is proposed to account for the involuntary contractions yet allow neurally triggered unitary voiding contractions in the overactive detrusor. Superimposed degeneration is proposed as the structural basis of impaired detrusor contractility, when also present.

Effects of partial outlet obstruction of the rat urinary bladder on micturition characteristics, DNA synthesis and the contractile response to field stimulation and pharmacological agents

Partial outlet obstruction is one of the major urological complications induced by benign prostatic hypertrophy (BPH). The current study describes the time course of the effect of mild partial outlet obstruction (in rats) on in vivo micturition parameters, DNA synthesis, and on the in vitro response of the bladder to field stimulation, bethanechol, methoxamine, ATP, and KCl. Mild partial outflow obstruction was created by placing a catheter (outside diameter: 1.70 mm.) transabdominally in front of the urethra, tying a ligature (2-zero silk) around both the urethra and catheter, and then removing the catheter. The micturition pattern was monitored for 2 days prior to surgery, and then continuously for 14 days following the surgery. The changes in bladder weight and the in vitro detrusor function of control (sham operated) and obstructed bladders (1, 3, 5, 7, 14 and 28 days after surgery) were examined. Micturition frequency in the dark cycle decreased immediately after the operation, and then increased linearly reaching a maximum at the 5th day, and stabilized at this increased level for the duration of the micturition study. The frequency of the dark cycle was also decreased immediately after the sham surgery and then gradually increased over the period of observation. Bladder weight increased by day 1 following surgery, and remained high throughout the 28 day study. The contractile response of the obstructed bladder base to field stimulation was reduced at days 1 and 3. The response then increased above control for day 5, reached a maximum response at day 7 and remained at this level for days 14 and 28. A similar pattern was observed for the contractile response of the bladder body to bethanechol and KCl, and for the bladder base to methoxamine and KCl. Both obstructed and sham surgeries increased bladder DNA content and 3H-thymidine incorporation, which reached maximal values on days 5 and 3, respectively. DNA content and 3H-thymidine incorporation of obstructed bladders were greater than those of sham operated bladders. In conclusion, partial outlet obstruction in the rat resulted in a progressive increase in bladder mass, an increase in micturition frequency, increases in the in vitro contractile response to field stimulation, bethanechol, methoxamine, and KCl, and increases in bladder DNA content and 3H-thymidine incorporation.

Effect of partial outlet obstruction on contractility: comparison between severe and mild obstruction

Detrusor dysfunction is one of the most common problems in patients with outflow obstruction secondary to benign prostatic hyperplasia. These patients complain of various symptoms, including urinary frequency, urge incontinence, difficulty in voiding, and retention. The severity of the symptoms is dependent on the stage of disease and/or severity of the obstruction. We compared the changes in the rat detrusor function following both mild and severe models of partial outlet obstruction in the rat. Outflow obstructions were created by ligation of the urethra over which a catheter was placed. The size of the catheter determined whether the severity of obstruction was mild or severe (1.70 mm for mild obstruction and 1.09 mm for severe obstruction). Changes in the bladder weight, length-tension relationships, and the contractile response to field stimulation, pharmacologic agonists, and KCl were studied in bladders isolated from 1 and 2 week obstructed rats. Bladder weights of all obstructed rats increased significantly. The weight of the severe obstructed rats were significantly greater than rats subjected to mild obstruction. In general, passive length-tension curves of obstructed rats were shifted to right. The magnitude of the active tension induced by high KCl was higher in the mild obstruction and lower in the severe obstruction. The maximum response to KCl of mild obstruction was generated at greater lengths than for the other groups. In general, the contractile responses of the mild obstructed bladder body to field stimulation, bethanechol, KCl, and ATP, and of the bladder base to field stimulation, KCl, and methoxamine, were significantly increased when compared to the responses of the control bladder body and base. However in the severe obstructed bladder, the responses to field stimulation, KCl, ATP, and methoxamine were significantly reduced from the responses of the control strips; the response to bethanechol was similar for control and the severe obstructed groups. In conclusion, the severity of outlet obstruction significantly altered the contractile response of the bladder. Mild obstruction induced a mild increase in bladder mass, which was associated with significant increases to all forms of stimulation. Severe outflow obstruction induced a substantial increase in bladder mass and a significantly greater reduction in the response to field stimulation than the response to bethanechol (which was unchanged).

Effects of acute in vitro overdistension of the rabbit urinary bladder on DNA synthesis

Urinary bladder outflow obstruction induces a myriad of structural and functional changes in the organ. Among the morphological responses to outlet obstruction is both hyperplasia and hypertrophy of specific cellular elements. The initial event which has been implicated in the initiation of the response to outflow obstruction is an initial period of high intravesical pressure and subsequent distention of the bladder. In a previous study, it was shown that at one day following partial outlet obstruction there was a marked increase in thymidine labelling of the urothelium, at 3-5 days, the labeling shifted from the urothelium to the interstitial and serosal elements. The current study was designed to determine if acute distention of the urinary bladder can induce an increase in DNA synthesis (3H-thymidine incorporation), and localize the increased DNA synthesis via autoradiography of 3H-thymidine. In this study, the bladders of adult male New Zealand white rabbits were mounted in isolated in vitro baths. Each control bladder was filled to either 5 or 20 ml. with saline, or distended to 120% of capacity. The bladders were incubated for 7 hours at which time 3H-thymidine was placed both within and outside the bladder for an additional one hour. At the end of the time the bladder was divided at the ureteral orifices into bladder body and base, and each body and base divided into two sections. One section of bladder body and base was quantitatively analyzed for both labelled and unlabelled DNA; the second section was fixed and prepared for autoradiography. The results can be summarized as follows: 1) Acute overdistention for 8 hours induced a slight decrease in the DNA concentration which was mediated by edema of the bladder wall. 2) Acute overdistention induced a 5-fold increase in 3H-thymidine incorporation in the bladder body and a 3-fold increase in the bladder base. Radioautoradiography of the overdistended bladders showed significant and substantial labelling which was confined to the urothelial basal cells. The control bladders showed little or no labelling. These results are consistent with the theory that acute distention following partial outlet obstruction initiates the proliferative response of the bladder to outlet obstruction, and the urothelium is the initial target of the proliferative response. Functionally, the proliferative response may serve to maintain the structural as well as functional integrity of the bladder.

Bladder Wall Histology and Duration of Obstruction

In BPH patients, obstruction leads to a progressive modification in the structure of the bladder wall, with histo-pathological changes which are often irreversible. In order to detect these changes and their possible correlation with function, muscle biopsies of the bladder were taken from 28 patients during endoscopic resection for benign prostatic hyperplasia. The samples were examined by means of electron microscope to show ultrastructural charges. The magnitude of the lesions can be correlated to function, seriousness and duration of the obstruction. Detecting histo-pathological damage can justify earlier treatment in obstructed BPH patients, in order to avoid those bladder lesions, which are the probable cause of clinical disorders which may persist even after therapy of the adenoma.

Bladder wall abnormalities in myelodysplastic bladders: a computer assisted morphometric analysis

Myelodysplasia represents the most common cause of neurogenic bladder dysfunction in children. The specific histological features associated with myelodysplastic bladders have not been previously characterized. Our objective was to study the relationship between smooth muscle and connective tissue in control and myelodysplastic bladders using classical morphometric analysis with the assistance of an automated image analysis system. Gross histological analysis of the bladder specimens of normal stillborn fetuses showed organized muscle bundles embedded in a small amount of connective tissue. The bladder specimens of myelomeningocele stillborn fetuses showed a marked paucity of muscle bundles as well as a significantly diminished size of the muscle bundles. The myelomeningocele bladder specimens obtained from patients undergoing autopsy and those undergoing augmentation cystoplasty revealed significant interfascicular and pericellular infiltration of the smooth muscle by dense connective tissue. Quantitative morphometric analysis showed that the myelomeningocele stillborn fetuses have a significant increase in the volumetric content of connective tissue compared to control stillborn fetuses. The bladders of myelomeningocele patients who underwent autopsy or augmentation cystoplasty had a 3-fold increase in connective tissue when compared to normal controls. These findings reveal that structural changes in the histological components of the myelodysplastic bladder can be demonstrated not only in patients of varying ages undergoing autopsy or augmentation cystoplasty but also in the developing fetus. These findings enhance our understanding of the relationship of connective tissue proliferation to smooth muscle in the myelodysplastic bladder. We discuss the relationship of these findings to pathological detrusor morphology and detrusor dysfunction.

Effect of bladder outlet obstruction on the morphology, physiology, and pharmacology of the bladder

Bladder outlet obstruction secondary to benign prostatic hyperplasia induces numerous changes in bladder morphology, physiology, and pharmacology. These changes have been studied experimentally in various animal models, and while each species has advantages and disadvantages, it is unclear which is most like man. It has been shown that tissue hypertrophy leading to an increase in tissue mass develops rapidly after bladder outlet obstruction. Ischemia induced by the obstruction results in acute muscle dysfunction. The degree of functional impairment is directly related to the degree of tissue hypertrophy. However, the bladder contractile apparatus appears to have a surprising regenerative ability, such that recovery of bladder function becomes obvious 14 days after obstruction. Urodynamic changes include an increase in urinary frequency and voiding pressure and a decrease in voided volume. Clinically, involuntary bladder contractions are often present. Determination of which of these specific aspects of outlet obstruction the investigator is interested in studying will dictate the selection of the most appropriate animal model.