Changes in bladder contractility and compliance due to urethral obstruction: a longitudinal followup of guinea pigs

Influence of sildenafil on blood oxygen saturation of the obstructed bladder

Background

Blood oxygen saturation (BOS) is decreased in a low-compliant, overactive obstructed bladder. The objective of this study is to determine the effect of Sildenafil (SC) on bladder function and BOS) in an in vivo animal model of bladder outlet obstruction.

Methods

Thirty-two guinea pigs; sham operated (n = 8), sham operated + SC (n = 8), urethrally obstructed (n = 8) and urethrally obstructed + SC (n = 8) were studied during an 8 week period. BOS of the bladder wall was measured by differential path-length spectroscopy (DPS) before obstruction, at day 0, and at week 8. The bladder function was evaluated by urodynamic studies every week.

Results

Before surgery and after sham operation all study parameters were comparable. After sham operation, bladder function and BOS did not change. In the obstructed group the urodynamic parameters were deteriorated and BOS was decreased. In the group obstruction + SC, bladder compliance remained normal and overactivity occurred only sporadic. BOS remained unchanged compared to the sham group and was significantly higher compared to the obstruction group.

Conclusions

In an obstructed bladder the loss of bladder function is accompanied by a significant decrease in BOS. Treatment of obstructed bladders with SC yields a situation of high saturation, high bladder compliance and almost no overactivity. Maintaining the microcirculation of the bladder wall might result in better bladder performance without significant loss of bladder function. Measurement of BOS and interventions focussing on tissue microcirculation may have a place in the evaluation / treatment of various bladder dysfunctions.

[Functional results after temporary continuous drainage of the hypocontractile bladder. The potential rehabilitation of the detrusor]

BACKGROUND

Impaired bladder emptying is a common problem in older people and a challenging task in treatment. Conservative and medical treatment options have shown beneficial effects on micturition; however, in a substantial number of patients the effectiveness of these therapies is disappointing. In the end the decompensated bladder needs indwelling catheterisation. To study the effects on the detrusor function, we analysed the urodynamic data of 31 patients during long-term bladder drainage retrospectively.

PATIENTS AND METHODS

All 17 female and 14 male patients showed impaired detrusor contractility, enlarged bladder capacity, decreased sensitivity and a high post-void residual urine volume (PVR). After exclusion of an acute pathology, the patients were treated continuously with a suprapubic catheter for an average of 13.1 weeks. By urodynamic measurements before and after the drainage period, we analysed the filling parameters, pressure-flow patterns, PVR and detrusor contractility.

RESULTS

At the end of the drainage period, significant changes in the detrusor function were obvious. Compared with the pre-treatment situation, the bladder volume at first desire to void decreased from 306.92 ml to 281.7 ml and the maximum bladder capacity from 691.8 ml to 496.8 ml, respectively. The compliance of the detrusor muscle diminished in the same period of time from 65.6 ml/cmH2O to 51.8 ml/cmH2O. The PVR dropped by 227.2 ml in average. The maximum flow rate was 9.4 ml/s, and the maximum detrusor pressure increased slightly up to 23.6 cmH2O.

CONCLUSION

The continuous drainage of the bladder results in significant changes in the motoric as well as sensoric detrusor function. The reduced bladder capacity and the decreased PVR might be indications of a regenerating process of the detrusor. The long-term drainage of the bladder shows beneficial and therefore therapeutic effects. It still remains to be investigated on a functional as well as structural basis to what extent age, gender and pathogenesis influences the rehabilitation of the detrusor.

Detrusor glycogen reflects the functional history of bladders with partial outlet obstruction

OBJECTIVE

To assess the relationship between glycogen content in bladder detrusor tissue and historical bladder function in a guinea-pig model of partial bladder outlet obstruction (PBOO).

MATERIALS AND METHODS

In male immature guinea pigs PBOO was created with a silver ring around the proximal urethra; a control group had a sham operation for comparison. Longitudinal individual urodynamic data were obtained weekly, so that guinea pigs were killed at different levels of bladder dysfunction. Bladder sections were stained with periodic acid-Schiff (PAS) to assess overall morphology and glycogen granule density, scored from 0 (no glycogen) to 3. Glycogen scores were related to both the end-stage and historical extremes of bladder function values.

RESULTS

Glycogen granules were seen only in the detrusor; as their number increased their location expanded from only close to the serosa (glycogen score 1), through the detrusor (score 2) up to the urothelium (score 3). A glycogen score of 0 correlated with normal values for all urodynamic variables. Compared with a glycogen score of 0 a score of 1 correlated with significant (P < 0.05) changes in end-stage compliance (decrease) and contractility (increase) and significantly higher historical values for contractility, pressure and number of unstable contractions (NUC). In the group with a glycogen score of 2 there were significant changes in both the end-stage values and historical extremes for compliance, pressure, contractility and NUC (all P < 0.05). In the group with a glycogen score of 3 all these changes were even more dramatic, except for the end-stage contractility, for which the increase was not significant. From glycogen score 0 to score 3 all changes increased in magnitude.

CONCLUSION

A high glycogen content reflects a history of abnormal urodynamic function. This finding exemplifies the added value of structural analysis to urodynamic studies. Further studies are needed to relate bladder structure to the potential for functional recovery.

The role of nitric oxide in bladder urothelial injury after bladder outlet obstruction

OBJECTIVE

To investigate the role of nitric oxide (NO) in the pathogenesis of injury to the bladder mucosa after bladder outlet obstruction (BOO).

MATERIALS AND METHODS

The response of bladder mucosa to BOO consists of thickening with fibrous connective tissue; NO is a multipurpose messenger important in blood vessel relaxation, neuronal communication and inflammatory activities of macrophages, and is synthesized by NO synthase (NOS), with three distinct isoforms; inducible (iNOS), endothelial (eNOS) and neuronal (nNOS). Fifteen male guinea pigs had a silk ligature placed around the bladder neck to induce BOO; controls included five sham-operated animals. The animals were killed at 2, 4, 6, 8 and 12 weeks after BOO. NADPH-diaphorase staining was used as a nonspecific method to determine NOS isoform distribution. Single- and double-label immunofluorescence histochemistry for iNOS, eNOS, nNOS and macrophage colony stimulating factor (M-CSF) were used, with laser scanning confocal microscopy to assess the results. The relative amount of iNOS mRNA was evaluated using reverse-transcription-polymerase chain reaction (RT-PCR), and a standard method to determine the degree of apoptosis.

RESULTS

Bladder mucosa had a markedly increased intensity of NADPH-diaphorase staining 2 weeks after BOO. iNOS immunoreactivity was markedly greater in the bladder mucosa 2 weeks after BOO than in controls. The immunolocalization of iNOS and M-CSF was identical in bladder mucosa after BOO. RT-PCR showed stronger iNOS mRNA expression in the obstructed bladder mucosa 2 weeks after BOO than in controls. eNOS and nNOS expression was detected only 8 weeks after BOO, with markedly more immunoreactivity 12 weeks after initiating BOO. Increased eNOS and nNOS immunoreactivity strongly correlated with the induction of apoptosis in the bladder mucosa.

CONCLUSION

There was overexpression of iNOS by activated macrophages in the early stages of BOO. This overexpression did not induce apoptosis in the iNOS-expressing cells of bladder mucosa in the early stages. After long-term BOO bladder mucosa showed strong eNOS and nNOS immunoreactivity, correlating with apoptosis. Thus we suggest that eNOS and nNOS, by triggering cell death, may be important in eliminating hyperplastic urothelial cells, reflecting the plasticity of the bladder response to obstructive stimuli.