Botulinum toxin type A injections into the urethral sphincter for idiopathic chronic non-obstructive urinary retention

Idiopathic non-obstructive urinary retention is the inability to completely empty the bladder when there is no physical obstruction (in the urethra or bladder neck) to normal urine flow. It can be caused by urethral sphincter dysfunction. This can be because of dysfunctional voiding, urethral sphincter hyperactivity or inadequate relaxation of the urethral sphincter (for example, Fowler's syndrome in younger women and people with female anatomy), or bladder functional problems (detrusor muscle underactivity, or detrusor hyperreflexia and inadequate contractility). But the specific underlying cause of the condition is unknown. Idiopathic non-obstructive urinary retention is often asymptomatic, but some people have lower abdominal discomfort and pain. Also, it can cause complications such as recurrent urinary tract infections and chronic kidney disease.

Current treatments for non-obstructive urinary retention include urotherapy (that is, education and rehabilitation for bladder and bowel management), an alpha-adrenoreceptor blocker medicine, urethral dilatation or clean intermittent catheterisation. When the condition is refractory to these treatments, it may be treated with sacral nerve stimulation or urinary diversion procedures.

Botulinum toxin type A injection into the urethral sphincter for idiopathic chronic non-obstructive urinary retention is usually done as an outpatient procedure with the person awake and lying in the lithotomy position. A local anaesthetic is used on either side of the external meatus. Botulinum toxin type A diluted with normal saline is injected directly into the external urethral sphincter using a syringe needle. A transperineal route (guided by electromyography) is used in women and a transurethral route (using electrical stimulation and cystoscopy guidance) is used in men.

The dose and number of injections used, and the depth and the position of injections on the endoscopic ultrasound, vary and depend on the discretion of the clinician. People have oral antibiotics for a week. The aim of the procedure is to relax the sphincter muscle and restore voiding function. It may be repeated every few months.