Title : The bladder cooling reflex and its clinical application
Abstract:
The ice-water test is a simple supplementary urodynamic test that is useful in differenting neurogenic from non-neurogenic bladder dysfunctions. Bors and Blinn some 50 years ago reported that rapid filling of the bladder with a small volume of ice water caused an immediate reflex detrusor contraction in patients with spinal upper motor neuron lesion but no response in those with lower motor neuron lesion or in neurologically normal subjects. A similar bladder cooling reflex has recently been characterised in the cat and was found to originate from specific cold receptors in the bladder wall. This presentation is a review of the physiology of the bladder cooling reflex and its clinical applications.
Materials and Methods: Adult cats under alpha-chloralose anesthesia were used for experiments. Two thin catheters were inserted into the bladder through a slit in the proximal urethra, one for bladder pressure recording, the other for bladder infusions of saline at different temperatures. Infusion evoked afferent and efferent nerve activity was recorded simultaneously from pelvic nerve branches to the bladder.
Clinically, the bladder cooling test was applied as a complement to routine cystometry both in children and adults. The outcome was evaluated retrospectively by members of our group. A total of 284 children with nonneurogenic and 108 with known or suspected neurogenic bladder dysfunction, ranging in age from 1 month to 18 years, were included together with 557 adults with overactive bladders, lower motor neuron lesions or pure stress incontinence. In adults, the bladder cooling test was performed as a rapid manual infusion of 100 ml cold saline (3 - 10O C), while for children about half the cystometric capacity was used after pretesting with an equal volume of body-warm fluid. The test was considered positive if the fluid was expelled from the bladder within 1 min or if a detrusor contraction greater than 30 cm H2O was evoked by the cold but not warm fluid.
Results: In the cat, reflex detrusor contractions were more readily evoked by infusions of cold than body-warm saline into the bladder. The threshold volume was lower and the efferent activity poorly correlated to the mechanoreceptor response showing prolonged after activity on bladder unloading. The cooling reflex was greatly exaggerated by intraluminal exposure of the bladder or the urethra to menthol (0.6 mM), which shifted the temperature-response curve towards higher temperatures. Afferent recordings demonstrated that cooling or menthol exposure activated a subgroup of unmyelinated C-afferents in the bladder pelvic nerve. Electrical stimulation at appropriate intensity revealed a corresponding bladder C-fibre reflex that survived an acute spinalization at a low thoracic level. Thus, the bladder cooling reflex is mediated by a segmental spinal pathway, partly separate from the ordinary micturition reflex.
Clinical studies in young children revealed that the bladder cooling test is positive during the first 2 years of life but typically becomes negative when the child gains voluntary control of its bladder. In neurologically intact adults the test is negative. It was positive in more than 90 % of patients with complete or incomplete upper motor neuron lesions and in about 75% of patients with multiple sclerosis, Parkinson's disease or previous cerebrovascular accident resulting in bladder hyperreflexia. Neither infusion speed nor infused volume was critical for the outcome of the test in such patients, provided that the bladder wall was sufficiently cooled. Thus, in adults, a positive test indicates overt or occult neuropathy.
Conclusions: The urinary bladder is equipped with a reflex system originating from cold receptors in the bladder wall and having a reflex pathway partly separate from that of the normal micturition reflex. The human bladder cooling reflex is in principle organized in the same way as that of laboratory animals. A positive bladder cooling test is an infant reflex response that becomes suppressed by descending signals from higher centers during maturation of the central nervous system. Excluding the age of factor, a positive test in patients with voiding dysfunction is an indicator of a latent or overt neurological disorder.
The bladder cooling test (“ice water test”) is a rapid and simple test, easy to interpret and well tolerated by patients. The test increases the precision of urodynamic evaluations.
What will audience learn from your presentation?
To learn bladder colling reflex.
1. What´s the triggering stimlus? Bladder tension, or bladder cooling?
2. Where are the bladder cooling receptors? Bladder and urethral walls, or structures around the bladder and urethra?
3. What type of receptors are involved? Ad fiber or C fiber cold receptors, or nociceptors (pain receptors)?
The benefits of bladder cooling test (BCT):
- The BCT is a simple and rapid add-on test
- Its outcome is easy to interpret
- It is well tolerated by patients
- The underlying physiology is reasonably well known
- It can in doubtful cases differentiate upper from lower motor neuron lesions
- It can varify a neurogenic etiology in certain types of urge incontinence
