A novel animal model of underactive bladder: analysis of lower urinary tract function in a rat lumbar canal stenosis model.

AIMS: An animal model of neurogenic underactive bladder (UAB) has not been established. It was reported that a rat lumbar spinal canal stenosis (LCS) model created by cauda equina compression manifested intermittent claudication and allodynia. In this study, we examined the lower urinary tract function of the rat LCS model. METHODS: One small hole was drilled at the fifth lumbar vertebral arch (sham), and a rectangular piece of silicone rubber was inserted into the L5-L6 epidural space (LCS). Before and after surgery, a metabolic cage study was performed. After surgery, awake cystometry (CMG) and an in vitro muscle strip study were performed. Bladder morphology was evaluated by hematoxylin and eosin staining. RESULTS: The LCS rats showed a significant decrease in voided volume and a significant increase in postvoid residual volume and residual urine rate compared with Sham rats. CMG showed that the postvoid residual urine volume and numbers of non-voiding contractions significantly increased, while the voided volume, threshold pressure, and maximum intravesical pressure during voiding significantly decreased. There were no significant differences between sham and LCS rats in response to carbachol. In contrast, there was a significant increase in response to field stimulation, especially at lower frequencies, in LCS rats. LCS rats showed no obvious difference in detrusor morphology. CONCLUSIONS: This rat model requires a relatively simple surgical procedure and has characteristics of neurogenic UAB. It seems to be useful in the pathophysiological elucidation of UAB and might have potential for assessment of pharmacotherapy of UAB.

Preliminary study of a genetically engineered spinal cord implant on urinary bladder after experimental spinal cord injury in rats.

The objective of this study was to determine the effect of neurotrophin-secreting Schwann cell implants on the urinary bladder after spinal cord contusion. One hour after severe spinal cord contusion at the T8 to T11 level, carbon filaments containing nonsecreting Schwann cells, brain-derived neurotrophic factor (BDNF)-secreting Schwann cells, neurotrophin-3 (NT-3)-secreting Schwann cells, or Schwann cells secreting both BDNF and NT-3 were implanted into the spinal cord. Untreated spinal cord injured (SCI) rats and noncontused rats (C) were also studied. Two months after spinal cord injury, cystometry was performed and the bladders were studied using light microscopy. SCI rats had significantly increased bladder mass, thickness, and smooth muscle mass compared to C rats. Bladder capacity of SCI rats and rats with spinal cord implants were both significantly greater than that of C rats. This preliminary study suggests that neurotrophin-secreting Schwann cell implants may lead to improved bladder structure after spinal cord injury.

Comparative efficacy and safety of extended-release and instant-release tolterodine in children with neural tube defects having cystometric abnormalities.

AIM: To evaluate the comparative efficacy and safety of extended-release (ER) and instant-release (IR) tolterodine preparations in a pediatric population with neural tube defects having cystometric abnormalities. MATERIALS AND METHODS: Twenty-five patients with neural tube defects and a similar demographic profile underwent a routine hemogram, liver function tests, renal function tests, urine culture, X-ray lumbo-sacral spine, and renal and bladder ultrasound. Vesicoureteric reflux was diagnosed by micturating cystourethrogram under fluoroscopy. Dimercaptosuccinic acid renal scintigraphy was performed to study the presence or absence of renal scars. Patients were treated with tolterodine ER (Group I: 2mg once daily for 21 days) and tolterodine IR (Group II: 2mg twice daily for 21 day) in a cross-over study with a 10-day washout period between administrations. Evaluation was by subjective assessment, visual analog scale, urodynamic assessment and adverse drug reaction monitoring. RESULTS: There was ultrasound evidence of hydroureteronephrosis in 20% of the patients. One patient out of 25 had impaired renal function and eight patients had renal scarring on dimercaptosuccinic acid scans. Both forms of the drug increased the maximum cystometric bladder capacity, decreased detrusor leak pressures and increased compliance compared to pre-therapy levels (P=0.0001). Visual analog scale showed a significant clinical improvement with both ER and IR tolterodine. A significant increase in maximum bladder capacity in the group receiving IR tolterodine as compared to the ER preparation was noted (P=0.0001). The decrease in detrusor leak pressures and improvement in compliance were not significantly different between the groups. No adverse effects of hyperpyrexia, flushing or intolerance to outdoor temperatures, or dryness of mouth were observed in either group. No patient suffered from constipation. CONCLUSION: ER tolterodine 2mg once daily is as effective and well tolerated in children with neurogenic bladder as IR tolterodine 2mg twice a day. The latter was found to be more effective in terms of urodynamic parameters. ER formulation of tolterodine is less expensive and has the advantage of single dosage.

Clinical efficacy and safety of tolterodine compared to oxybutynin and placebo in patients with overactive bladder.

This study compared the clinical efficacy (determined from micturition diaries) and safety of 12 weeks' treatment with either tolterodine 2 mg twice daily, oxybutynin 5 mg three times daily or placebo in patients with an overactive bladder. A total of 277 patients were randomized and treated at 25 centers. Both tolterodine and oxybutynin significantly increased volume voided/micturition compared to placebo. Both treatment groups evoked greater decreases in micturitions per 24 hours and incontinence episodes per 24 hours compared to placebo; however, only tolterodine was significantly better than placebo in reducing micturition frequency. Tolterodine and oxybutynin were equivalent in their effectiveness. Tolterodine was significantly better tolerated than oxybutynin when adverse events (particularly frequency and intensity of dry mouth), dose reduction and patient withdrawals were considered. Oxybutynin is an effective drug whose frequent adverse effects limit its clinical usefulness. Tolterodine has equivalent efficacy to oxybutynin, but with less severe adverse effects. This will allow patients to receive more effective treatment for their condition, with better compliance.