Urodynamic follow-up of experimental urethral obstruction in individual guinea pigs

Congenital peritoneal encapsulation: A review and novel classification system

Congenital peritoneal encapsulation (CPE) is a very rare, congenital condition characterised by the presence of an accessory peritoneal membrane which encases a variable extent of the small bowel. It is unclear how CPE develops, however it is currently understood to be a result of an aberrant adhesion in the peritoneal lining of the physiological hernia in foetal mid-gut development. The condition was first described in 1868, and subsequently there have been only 45 case reports of the phenomenon. No formal, systematised review of CPE has yet been performed, meaning the condition remains poorly understood, underdiagnosed and mismanaged. Diagnosis of CPE remains clinical with important adjuncts provided by imaging and diagnostic laparoscopy. Two thirds of patients present with abdominal pain, likely secondary to sub-acute bowel obstruction. A fixed, asymmetrical distension of the abdomen and differential consistency on abdominal palpation are more specific clinical features present in approximately 10% of cases. CPE is virtually undetectable on plain imaging, and is only detected on 40% of patients with computed tomography scan. Most patients will undergo diagnostic laparotomy to confirm the diagnosis. Management of CPE includes both medical management of the critically-unstable patient and surgical laparotomy, partial peritonectomy and adhesiolysis. Prognosis following prompt surgical treatment is excellent, with a majority of patients being symptom free at follow up. This review summarises the current literature on the aetiology, diagnosis and treatment of this rare disease. We also introduce a novel classification system for encapsulating bowel diseases, which may distinguish CPE from the commoner, more morbid conditions of abdominal cocoon and encapsulating peritoneal sclerosis.

Development of an Improved Animal Model of Overactive Bladder: Transperineal Ligation versus Transperitoneal Ligation in Male Rats

Purpose

We compared a transperineal ligation model and a transperitoneal ligation model in male rats to determine which animal model of overactive bladder (OAB) was more useful based on cystometrography, estimations of oxidative stress, and measurements of pro-inflammatory cytokine levels.

Materials and Methods

Male rats were randomly divided into three groups (n=15 in each): the control group, the transperineal ligation group, and the transperitoneal ligation group. Four weeks after the ligation procedure, cystometrography was performed and oxidative stress, pro-inflammatory cytokine levels, and histologic changes were evaluated. Oxidative stress was assessed by measuring 8-hydroxy-20-deoxyguanosine and superoxide dismutase, and pro-inflammatory cytokine activity was investigated by measuring levels of interleukin (IL)-6, IL-8, and tumor necrosis factor-α.

Results

The transperineal model led to results similar to those observed for the transperitoneal model, namely (1) increased voiding frequency and reductions in the non-voiding contraction interval and the maximal vesical pressure, (2) increased levels of oxidative stress markers, (3) increased pro-inflammatory cytokine levels, and (4) fibrotic changes in the bladder tissue.

Conclusions

We suggest that the transperineal procedure can be used as an alternative OAB model in male rats.

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.

Changes in bladder wall blood oxygen saturation in the overactive obstructed bladder

PURPOSE

Several studies suggest that hypoxia of the bladder wall contributes to bladder dysfunction but the exact relation between bladder function and blood oxygen saturation, a surrogate marker for hypoxia, is not known. We determined bladder wall blood oxygen saturation in vivo in an animal model of bladder outlet obstruction to establish the exact relation between blood oxygen saturation and bladder function.

MATERIALS AND METHODS

In 8 sham operated and 8 urethrally obstructed guinea pigs we measured blood oxygen saturation of the bladder wall by differential path length spectroscopy before surgery and 8 weeks postoperatively. Urodynamic investigations performed during the whole 8-week period provided data on bladder function.

RESULTS

Before surgery and 8 weeks after sham surgery blood oxygen saturation in the bladder wall was between 88% and 95% during filling. It decreased during voiding and returned to greater than 90% within 30 seconds. Eight weeks after obstruction saturation was significantly lower than in the sham operated group during filling and voiding. The decrease was positively related to bladder pressure during filling and voiding, and was more pronounced when overactivity was present. Local bladder contractions occurred without a measurable increase in bladder pressure but were associated with a decrease in saturation.

CONCLUSIONS

A normal bladder maintains a high oxygen saturation level during filling. Bladder obstruction compromises this ability, especially when it involves overactivity. Local bladder contractions without a measurable increase in bladder pressure were associated with a decrease in blood saturation.

Animal models in overactive bladder research

Overactive bladder syndrome (OAB) is a symptom-based diagnosis characterised by the presence of urinary urgency. It is highly prevalent and overlaps with the presence of bladder contractions during urine storage, which characterises the urodynamic diagnosis of detrusor overactivity. Animal models are needed to understand the pathophysiology of OAB, but the subjective nature of the symptom complex means that interpretation of the findings in animals requires caution. Because urinary urgency cannot be ascertained in animals, surrogate markers such as frequency, altered toileting areas, and non-micturition contractions have to be used instead. No model can recapitulate the subjective, objective, and related factors seen in the clinical setting. Models used include partial bladder outlet obstruction, the spontaneous hypertensive rat, the hyperlipidaemic rat, various neurological insults and some gene knock-outs. Strengths and weaknesses of these models are discussed in the context of the inherent difficulties of extrapolating subjective symptoms in animals.

Phenotypic variation of colonic motor functions in chronic constipation

BACKGROUND & AIMS

Colonic motor disturbances in chronic constipation (CC) are heterogeneous and incompletely understood; the relationship between colonic transit and motor activity is unclear. We sought to characterize the phenotypic variability in chronic constipation.

METHODS

Fasting and postprandial colonic tone and phasic activity and pressure-volume relationships were assessed by a barostat manometric assembly in 35 healthy women and 111 women with CC who had normal colon transit (NTC; n = 25), slow transit (STC; n = 19), and defecatory disorders with normal (DD-normal; n = 34) or slow transit (DD-slow; n = 33). Logistic regression models assessed whether motor parameters could discriminate among these groups. Among CC, phenotypes were characterized by principal components analysis of these measurements.

RESULTS

Compared with 10th percentile values in healthy subjects, fasting and/or postprandial colonic tone and/or compliance were reduced in 40% with NTC, 47% with STC, 53% with DD-normal, and 42% with DD-slow transit. Compared with healthy subjects, compliance was reduced (P <or= .05) in isolated STC and DD but not in NTC. Four principal components accounted for 85% of the total variation among patients: factors 1 and 2 were predominantly weighted by fasting and postprandial colonic phasic activity and tone, respectively; factor 3 by postprandial high-amplitude propagated contractions; and factor 4 by postprandial tonic response.

CONCLUSIONS

Fasting and/or postprandial colonic tone are reduced, reflecting motor dysfunctions, even in NTC. Colonic motor assessments allow chronic constipation to be characterized into phenotypes. Further studies are needed to evaluate the relationship among these phenotypes, enteric neuropathology, and response to treatment in CC.

The effect of oxybutynin on structural changes of the obstructed guinea pig bladder

PURPOSE

Oxybutynin is used clinically to lower intravesical pressure and detrusor overactivity. In vitro it inhibits stretch induced bladder smooth muscle cell proliferation. We tested whether oxybutynin also prevents hypertrophic bladder changes in vivo in a model of partial bladder obstruction.

MATERIALS AND METHODS

Subvesical obstruction was induced in immature guinea pigs by a silver ring around the urethra. Eight animals received 0.4 mg oxybutynin per kg body weight per day in 2 doses. Control groups were obstructed without oxybutynin treatment or sham operated. Urodynamic pressure flow studies were performed at 1-week intervals for 10 weeks in all animals under anesthesia with ketamine/xylazine. After 10 weeks the animals were sacrificed and the bladder was removed for structural analysis with periodic acid-Schiff stain, in which the number of glycogen granules was also scored as a measure of previous ischemia.

RESULTS

Compared to the sham treated group obstructed animals had significantly higher intravesical pressure and detrusor overactivity, lower compliance and increased contractility. Obstructed animals that received oxybutynin retained normal intravesical pressure, detrusor overactivity and compliance. Their bladder contractility increased as in obstructed animals. The oxybutynin group showed less collagen infiltration in the detrusor and fewer glycogen granules compared to those in obstructed animals.

CONCLUSIONS

Our results demonstrate that oxybutynin has a protective effect on bladder function and structure. Prevention of hypertrophic and ischemic bladder changes is an argument for an early start of oxybutynin treatment in children with inborn neurogenic bladder dysfunction, such as spina bifida, or in patients with urethral valves.

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.

Abnormal urine flow in boys with distal hypospadias before and after correction

PURPOSE

We established the urine flow rate and the effect of surgical correction on that rate in patients with hypospadias.

MATERIALS AND METHODS

The urine flow rate, voided volume and residual urine were measured using an ultrasound flow probe and bladder scan in boys with distal hypospadias before operative correction in 42 with a mean age of 16 months, 3 and 9 months after operative correction in 28 and 11, respectively, and in a control group of 51 boys 0 to 3 years old (mean age 11 months). Long-term flow data were obtained retrospectively from the records of 63 patients with hypospadias 1 to 10 years after operation.

RESULTS

Of the controls 37% had mainly intermittent and sometimes fractionated flows, 4% had a plateau phase flow and 59% had mainly bell-shaped flow curves. The average maximum flow rate +/- SD was 6.8 +/- 4.1 ml per second and maximum flow rate/voided volume was 0.26 +/- 0.11 l per second. Of the boys with distal hypospadias 76% produced intermittent flows (fractionated in the majority) before correction. After correction this percent decreased to 50%. The average maximum flow rate was 7.5 +/- 2.5 ml per second before correction, and 6.6 +/- 2.8 and 7.2 +/- 1.8 ml per second 3 and 9 months after operation, respectively. Average maximum flow rate/voided volume was 0.22 +/- 0.12 l per second before, and 0.16 +/- 0.09 and 0.16 +/- 0.09 l per second 3 and 9 months after operation, respectively. In the long-term group maximum flow rate/voided volume was 0.13 +/- 0.11 l per second. The number of patients voiding with a plateau phase increased from 6% before to 13% and 17% after correction, respectively. An obstructive pattern was also observed in 41% of the long-term followup group.

CONCLUSIONS

An intermittent flow pattern is common in 0 to 3-year-old boys. It appears to be more common and more pronounced or fractionated in boys with distal hypospadias at the same ages. In relation to voided volume patients with hypospadias already produce an abnormally low urine flow rate before correction and even more so thereafter in the short and intermediate term. The corrective procedure increases the occurrence of flows with an obstructive pattern.

Animal models in urological disease and sexual dysfunction

There are several conditions associated with dysfunction of the lower urinary tract or which result in a reduction in the ability to engage in satisfactory sexual function and result in significant bother to sufferers, partners and/or carers. This review describes some of the animal models that may be used to discover safe and effective medicines with which to treat them. While alpha adrenoceptor antagonists and 5-alpha-reductase inhibitors deliver improvement in symptom relief in benign prostatic hyperplasia sufferers, the availability of efficacious and well-tolerated medicines to treat incontinence is less well served. Stress urinary incontinence (SUI) has no approved medical therapy in the United States and overactive bladder (OAB) therapy is limited to treatment with muscarinic antagonists (anti-muscarinics). SUI and OAB are characterised by high prevalence, a growing ageing population and a strong desire from sufferers and physicians for more effective treatment options. High patient numbers with low presentation rates characterizes sexual dysfunction in men and women. The introduction of Viagra in 1998 for treating male erectile dysfunction and the success of the phosphodiesterase type 5 inhibitor class (PDE5 inhibitor) have indicated the willingness of sufferers to seek treatment when an effective alternative to injections and devices is available. The main value of preclinical models in discovering new medicines is to predict clinical outcomes. This translation can be established relatively easily in areas of medicine where there are a large number of drugs with different underlying pharmacological mechanisms in clinical usage. However, apart from, for example, the use of PDE5 inhibitors to treat male erectile dysfunction and the use of anti-muscarinics to treat OAB, this clinical information is limited. Therefore, current confidence in existing preclinical models is based on our understanding of the biochemical, physiological, pathophysiological and psychological mechanisms underlying the conditions in humans and how they are reflected in preclinical models. Confidence in both the models used and the pharmacological data generated is reinforced if different models of related aspects of the same disorder generate confirmatory data. However, these models will only be fully validated in retrospect once the pharmacological agents they have helped identify are tested in humans.

Pre-selection of patients for pressure-flow analysis based on the maximum flow rate

OBJECTIVE

To study the effects of the application of flow rate prescreening to select men for invasive pressure-flow studies, notably the reduction of invasive pressure-flow measurements that can be achieved and the proportion of men in whom, on the basis of the application of a prescreening, an invasive measurement is unjustly not indicated (false negatives). In addition, the variables on which these effects depend are studied.

MATERIALS AND METHODS

Two hundred and sixty-two pressure-flow measurements in 131 patients (2 measurements/patient) and 89 free-flow measurements that preceded the invasive measurements in some patients were studied. A mathematical model was developed based on the outcomes of the invasive measurements. By means of the model the effects of several flow rate prescreening scenarios were estimated. A comparison of the model predicted and actually observed effects of flow rate prescreening was made for those measurements that were preceded by a free-flow rate measurement.

RESULTS

The application of a free-flow rate prescreening may result in a reduction of the number of invasive measurements of 20-30% at a 5% false negative rate. The reduction that may be achieved at an assumed constant false negative rate depends on the distribution of the maximum flow rate in the population and on the definition of bladder outlet obstruction used. When the measurement selection procedure was applied to the free-flow rate measurements that were available in 89 patients, a 21% reduction in invasive measurement indications was found (25% expected). Four patients (4.5%) would have been unjustly excluded from invasive procedures (maximally 5% expected), three of these four patients were borderline obstructed.

CONCLUSION

Considering the bother and risk to the patient and the cost of invasive measurements we think that a 20-30% gain in efficiency at a 5% risk of unjustly declaring a patient unobstructed makes a flow rate prescreening procedure cost effective in the diagnosis of bladder outlet obstruction.

Identification of bladder wall layers by Raman spectroscopy

PURPOSE

We explored the applicability of Raman spectroscopy to in situ investigation of bladder wall tissue.

MATERIALS AND METHODS

Bladder wall tissue was obtained from a guinea pig model and frozen sections were used for Raman spectroscopic investigations. From each section 500 to 700 spectra were obtained in a 2-dimensional grid spanning the urothelium, lamina propria and muscle layer. The data set of spectra was subdivided into groups of similar spectra by a cluster analysis algorithm. With each group assigned a different color Raman maps of frozen sections were constructed based on group membership of measured spectra. These maps were then compared with histological and histochemical data obtained from hematoxylin and eosin and immunohistochemical staining for collagen I and III and for smooth muscle actin to correlate Raman spectral features with bladder wall structure and molecular composition.

RESULTS

Urothelium, lamina propria and muscle layers could be clearly distinguished based on Raman spectra. Lamina propria spectra were dominated by signal contributions of collagen and the smooth muscle layer showed strong signal contributions of actin. The urothelium had a relatively strong lipid signal contribution.

CONCLUSIONS

These results and the fact that Raman spectroscopy is rapidly evolving into a technology that can be applied in vivo by thin, flexible fiberoptic catheters indicate that prospects are good for in vivo analysis of the molecular composition of the normal and pathological bladder without biopsies.