Which is CORRECT for the artificial urinary sphincter (AUS)?
Answer A
The bulbar urethra is the preferred cuff implantation site in post-prostatectomy incontinence. In neuropaths, in particular after spinal cord injury, patients are mostly wheelchair bound thus sitting with the whole-body weight on the bulbar urethra. Moreover, neuropathic patients often have an open bladder neck, especially in patients with infrasacral lesions. Consequently, the prostatic urethra is always filled with urine, which may possibly be a factor for recurrent infection and prostatic influx in male patients. Therefore, in neuropaths, the AUS cuff is placed at the bladder neck. The infection rate is 1%–5%. In non-neuropaths, the erosion rate is also 1%–5% but is higher in neuropaths. It is possible to place an artificial urinary sphincter at the same time whilst performing a cystoplasty. However, there can be an increased risk of infection and the patient must be warned accordingly
Which of the following statements is CORRECT with respect to sacral anterior root stimulator (SARS)?
SARS is also known as the Brindley or Finetech-Brindley stimulator. The sacral anterior root stimulator was developed by experiments on baboons in the MRC Neurological Prostheses Unit in London from 1969 to 1977.
Activation of the implant stimulates contraction of both the bladder and the external sphincter. However, because the bladder is composed of smooth muscle and the sphincter-striated muscle, sphincter contraction is relatively short, and the detrusor continues to contract (and therefore empty) long after sphincter contraction is complete. This improves bladder emptying, reduces residual volume and infection and lowers transmitted upper tract pressures. The posterior roots are cut to control neurogenic overactivity. The improvement in bladder capacity and compliance is secondary to the dorsal rhizotomy and not the SARS.
The effects of implant activation on the bowel are increased colonic activity, reduced constipation and sometimes defaecation during stimulation. Dorsal rhizotomy causes loss of reflex erection but activation of the implant will cause a penile erection.
Which is TRUE regarding anticholinergic medications?
M2 receptors are more abundant in the detrusor but M3 receptors are functionally more important. Anticholinergics work at muscarinic receptors to reduce the response to cholinergic stimulation, thus reducing detrusor contractions and detrusor pressure during filling. Oxybutynin has some selectivity for M1 and M3 receptor subtypes as well as direct smooth muscle relaxant affect, probably via calcium channel blockade. Randomised trials have confirmed the efficacy of oxybutynin at the expense of compliance due to side effect profiles. ER oxybutynin has comparable efficacy to immediate release but improved tolerability.
Tolterodine is not receptor specific but has greater affinity for the bladder compared to other organs. IR tolterodine has equivalent efficacy to oxybutynin with fewer side effects.
Solifenacin is an M3 receptor antagonist. The STAR trial was a prospective, doubleblind, 12-week study to compare efficacy and safety of solifenacin 5 or 10 mg and tolterodine ER 4 mg once daily in OAB patients. The study concluded that solifenacin had greater efficacy in decreasing urgency episodes, incontinence, urgency incontinence and pad usage and increasing the volume voided per micturition. Discontinuations were comparable and low in both groups.
Fesoterodine is a prodrug that is hydrolysed to the same active metabolite as tolterodine. [ER] = extended release; [IR] = immediate release; [OAB] = overactive bladder
Which is CORRECT regarding neuroanatomy of the bladder?
Answer B
The “wiring” of the bladder consists of an excitatory input by efferent parasympathetic nerves originating in the S2−S4 intermediolateral columns of the spinal cord. The sympathetic input to the bladder arises from neurons originating from the intermediolateral column of the T11−L2 spinal cord segments, in order to innervate the trigone and bladder neck smooth muscle.
The lower urinary tract is innervated by three types of peripheral nerves: parasympathetic (cholinergic) nerves, sympathetic (noradrenergic) nerves and somatic (cholinergic) nerves. The lateral border of the ventral horn (Onuf’s nucleus) is the origin of the cholinergic motor neurones to the external urethral sphincter. Fibres travel via the pudendal nerves (S2 and S3) to contract this sphincter.
The urodynamic trace below
demonstrates the following feature:
Answer D
The safety of the patient should be paramount during the study. There should be careful assessment of the patient’s ability to sit and stand safely and this should be documented in the report. The investigator should understand the phenomenon of autonomic dysreflexia (AD) and be competent to treat this life-threatening condition.
It is recommended to start filling at 20 mL/min with body warm fluid. This trace demonstrates a classical pattern of neurogenic detrusor overactivity and if accompanied with a video clip would have shown sphincter dyssynergia. There is a cough test in the beginning of the study with good subtraction. Ideally, the cough should be performed after every minute and at the end of the study to ensure optimal functioning of the lines. Although not clearly marked, it is unlikely more than 500 mL has been instilled in the bladder.
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