Influence of Urethral Sphincter Incompetence on Bladder Shape and Function in Myelodysplastic Children

Authors


Osamu Yokoyama, MD, PhD, Department of Urology, Faculty of Medical Science, University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji, Fukui 910-1193, Japan. Tel: +81-776-61-8396; Fax: +81-776-61-8126. Email: oyoko@u-fukui.ac.jp

Abstract

Objectives: This study was undertaken to investigate the influence of the urethral function on bladder shape and function in myelodysplastic children.

Methods: Of 39 myelodysplastic children, 30 were treated with intermittent catheterization. The diagnosis of internal sphincter incompetence (SI) was based on cystographic findings (open bladder neck) and that of external SI on urodynamic findings (underactive external sphincter identified on electromyography and maximum urethral closure pressure of less than 50 cm H2O). Follow up included evaluation of bladder deformity and compliance.

Results: The mean observation period was 8.6 years. In the 11 patients with external SI, bladder deformity and compliance significantly improved as a result of intermittent catheterization. However, of 12 patients with overactive sphincter and/or closure pressure of 50 cm H2O or more, eight showed deterioration or no improvement in bladder deformity, and three showed upper urinary tract deterioration.

Conclusion: These results indicate that an increase in urethral resistance may lead to deterioration of bladder shape.

1. INTRODUCTION

Sphincter incompetence (SI) in myelodysplastic children is associated with intractable urinary incontinence and has a deleterious effect on personal development in adolescents. Since the effects of pharmacological treatment, including anticholinergic or α-adrenergic prophylactics, are not always satisfactory, urinary incontinence caused by SI has been treated with uncertain results by bladder neck reconstruction, artificial sphincter, and polytetrafluoroethylene (Teflon) or collagen injection around the urethra.1–7 The sling procedure for SI, on the other hand, has become the treatment of choice for achieving continence,8,9 but many problems have yet to be solved such as making the operation time suitable for children and the management of concomitant operations (bladder augmentation). Furthermore, upper urinary tract changes have been reported in myelodysplastic patients treated by artificial sphincter.3,4 As a first step in finding solutions for these problems, we evaluated the influence of urethral function on bladder shape and function.

2. METHODS

Thirty-nine myelodysplasia patients (19 male and 20 female) were evaluated. The mean age at first visit to our clinic was 8.4 ± 1.3 (mean ± standard error of the mean) years old. Thirty patients were treated with intermittent catheterization, while the other nine patients were allowed to void voluntarily.

Urological evaluation, including excretory urography and urodynamic studies, was performed during the first visit to our clinic. The diagnosis of internal or external SI was based on cystography and urodynamic findings. We classified bladder deformity, such as trabeculation, as grade 0 (none), grade 1 (mild), grade 2 (moderate) or grade 3 (severe) on the basis of cystography.10,11 A spontaneously open bladder neck observed on erect cystography was considered a sign of incompetent internal sphincter.12

Cystometry was performed with physiological saline or carbon dioxide as the filling medium at a rate of 25–50 mL/min via an 8F catheter. Simultaneous electromyography (EMG) of the external sphincter was performed with two platinum wire electrodes inserted at the 3 and 9 o’clock positions on the sphincter. An underactive external sphincter was identified by the absence of increased sphincter EMG activity during bladder filling.9 Maximum urethral closure pressure was determined from the urethral pressure profile, which was measured with physiological saline at a rate of 5–10 mL/min. The diagnosis of external SI was based on both an underactive external sphincter and a maximum urethral closure pressure of less than 50 cm H2O.13

The patients treated with intermittent catheterization were divided into four groups according to the type of SI (Table 1). Group A consisted of patients with an incompetent internal and external sphincter. Group B consisted of patients with an incompetent internal sphincter, but without incompetency of the external sphincter. Group C consisted of patients with an incompetent external sphincter, but without incompetency of the internal sphincter. Group D consisted of patients without incompetency of either the internal or external sphincter. Follow ups included cystography and urodynamic studies to evaluate bladder deformity and compliance at least once a year.

Table 1.  Classification and characteristics of patients managed by intermittent catheterization
 Sphincter incompetencenMean age (years)Mean observation period (years)P-value
InternalExternal
  1. NS, not significant.

  2. NA, not applicable.

Group AYesYes315.3 ± 10.88.2 ± 5.4NA
Group BYesNo413.0 ± 5.35.6 ± 1.6NA
Group CNoYes118.6 ± 1.910.4 ± 1.3NS
Group DNoNo127.8 ± 1.68.5 ± 1.1NS

Data were expressed as mean ± standard error of the mean. Statistical significance was determined by Wilcoxon signed-ranks test or Mann-Whitney U-test. A level of P < 0.05 was considered statistically significant.

3. RESULTS

The mean observation period was 8.6 ± 1.2 years. Patients in group A and B were excluded from statistical analysis because of the small number of patients and large individual differences in mean age at the first visit to our clinic and in mean observation period. Mean age and mean observation period in group C were not significantly different from those in group D (Table 1). There were no significant differences in sex, level of spinal lesion or degree of neurological deficit between group C and D. To preserve the bladder as a low pressure storage organ we adopted prophylactic use of anticholinergic agents in patients treated with intermittent catheterization. Nine patients in group C and 10 in group D received anticholinergic agents.

The mean grade of bladder deformity at initial evaluation of group C was 1.6 ± 0.3 versus 1.3 ± 0.3 for group D (not significant; Fig. 1). Grade of bladder deformity at initial and final evaluation was compared for each group. Mean grade of bladder deformity of group C significantly decreased from 1.6 ± 0.3 to 0.5 ± 0.2 (P < 0.01) as a result of intermittent catheterization. However, the corresponding variable for group D only changed from 1.3 ± 0.3 to 1.4 ± 0.3 (not significant). Eight patients in group C showed evidence of improvement in bladder deformity, but eight in group D showed deterioration (three patients) or no improvement (five patients). One of the three patients showing deterioration showed detrusor-sphincter dyssynergia on cystometrography and EMG.

Figure 1.

Comparison of mean grade of bladder deformity at initial and final evaluation. Mean observation period was 10.4 years for group C (competent internal sphincter and incompetent external sphincter) and 8.5 years for group D (competent internal and external sphincter). Values represent mean ± standard error of the mean. NS, not significant.

Bladder compliance at initial evaluation of group C was 13.7 ± 3.5 mL/cm H2O versus 8.0 ± 1.4 mL/cm H2O for group D (not significant; Fig. 2). Bladder compliance at initial and final evaluation was compared in each group. Bladder compliance of group C significantly improved from 13.7 ± 3.5 to 28.9 ± 5.5 mL/cm H2O (P < 0.05), and that of group D also significantly improved from 8.0 ± 1.4 to 18.5 ± 3.4 mL/cm H2O (P < 0.05). Bladder compliance at final evaluation was significantly higher in group C than in group D (P < 0.05).

Figure 2.

Comparison of bladder compliance at initial and final evaluation. Mean observation period was 10.4 years for group C (competent internal sphincter and incompetent external sphincter) and 8.5 years for group D (competent internal and external sphincter). Values represent mean ± SEM.

Three of the 11 patients in group C, and four of the 12 in group D showed signs of vesicoureteral reflux (VUR) during their first visit to our clinic. Two patients in group C showed no reflux after a mean observation of 5.1 years, while the reflux grade progressed for one patient and remained unchanged for three patients in group D. Two patients in group D developed minor ureteral dilatation after the start of intermittent catheterization.

4. DISCUSSION

Intermittent catheterization has been recommended for maintaining low storage and voiding pressure, which result in a reduction in incontinence volume. However, refractory incontinence persists in many myelodysplastic patients, even in those on intermittent catheterization. In myelodysplastic patients, urinary incontinence due to sphincter incompetence is a formidable social handicap and remains a challenging issue.

Many kinds of surgical procedures have been proposed for persistent incontinence: urinary diversion, augmentation cystoplasty, bladder neck reconstruction, artificial sphincter, facial sling procedure, and polytetrafluoroethylene (Teflon) or collagen injection around the urethra.1–9,12 Except for urinary diversion, the principle underlying these procedures is surgical augmentation of bladder outlet resistance at the bladder neck or proximal urethra resulting from direct urethral compression. The success of these procedures depends on elevation of the intraurethral pressure. However, among 45 children with an artificial sphincter, Bauer et al. found that six had elevated filling pressure which resulted in three children who developed hydronephrosis.3 Furthermore, 4 of 20 meningomyelocele patients who received artificial sphincter implantation developed hydronephrosis and severe impairment of renal function.4 The patients who showed deterioration in the upper urinary tract were managed by means of voluntary voiding. These findings suggest that upper urinary tract deterioration may be attributable to high vesical pressure in the storage and voiding phase. To address the question of whether an additional increase in urethral resistance leads to an improved prognosis for the urinary tract, influences of the intrinsic sphincter potency on bladder shape and function were investigated in this study.

Bladder deformity such as trabeculation is reported to be an early manifestation of neurogenic dysfunction in acute spinal cord injury,14 and to be related to bladder compliance.10 Cystography is believed to be important for the prediction of upper urinary tract deterioration.15 In our study, of the 12 patients with a overactive sphincter and/or urethral closure pressure of 50 cm H2O or more (group D), three showed signs of deterioration in bladder deformity, and five showed no change in bladder deformity even when they were treated with intermittent catheterization. The reflux grade progressed in one of these patients, and minor ureteral dilatation was shown in two patients after the start of intermittent catheterization. In contrast, the 11 patients with underactive sphincter and urethral closure pressure less than 50 cm H2O (group C) showed significant improvement in bladder deformity as a result of intermittent catheterization. Deterioration of the upper urinary tract was not detected in this group. These findings suggest that the high storage pressure caused by urethral resistance may affect bladder shape. Even though low amplitude detrusor waves may be observed, the urethral resistance preserved urinary continence, leading to high storage pressure in the bladder. For this reason myelodysplastic patients with a competent sphincter should be carefully monitored for bladder deformity, which is an early prognosticator of upper urinary tract deterioration. Furthermore, an increase in urethral resistance, resulting from surgical procedures, may lead to deterioration of bladder shape. A reduction in bladder capacity and compliance has been shown in neurogenic bladder patients managed only with the fascial sling procedure.9 Patients should therefore be carefully selected for surgical procedures designed to enhance urethral closure function.

In this study, the mean grade of bladder deformity did not improve and deterioration of the upper urinary tract was seen in three patients in group D, but bladder compliance improved significantly from 8.0 to 18.5 mL/cm H2O during the mean observation period of 8.5 years. Bladder compliance is defined as the change in volume per unit change in pressure during bladder filling as determined in urodynamic studies, and indicates the storage function of the bladder. Low bladder compliance is regarded as a strong prognosticator of upper urinary tract function in myelodysplastic patients at risk.16,17 However, it has been shown that bladder compliance is not relevant for the VUR in myelodysplastic patients.13 The bladder wall consists of collagen, elastin and smooth muscle in addition to epithelium, nerves and blood vessels. The interrelationship between these elements determines bladder compliance. In addition, the possibility exists that an episode of bladder overdistension and inflammation of the bladder mucosa may affect bladder compliance.18 Furthermore, bladder compliance may also increase with an increase in body weight as a result of growth. When the patients show huge VUR, bladder compliance can be underestimated. Since bladder compliance depends upon several factors, it may not necessarily correlate with prognosis for the urinary tract.

5. CONCLUSION

Our studies suggest that a high storage pressure caused by urethral resistance may lead to deterioration of bladder shape in patients with myelodysplasia.

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