Rigi10™ Malleable Penile Prosthesis
Also Known As
Bladder voiding, Urination, Micturition, Voiding function, Detrusor contraction and urethral relaxation, Urinary elimination
Definition
Bladder emptying is the physiological process by which urine is completely voided from the bladder through the coordinated contraction of the detrusor muscle and relaxation of the urethral sphincters.1 This complex process requires precise integration between the central nervous system (brain and spinal cord) and peripheral nervous system to achieve proper coordination.2 The micturition reflex, which controls bladder emptying, involves two distinct phases: the storage phase, where the bladder relaxes and fills with urine while the urethral sphincters remain contracted, and the voiding phase, where the detrusor muscle contracts while the urethral sphincters relax.3
The neural control of bladder emptying involves multiple pathways and neurotransmitters. Parasympathetic nerves from sacral segments S2-S4 provide excitatory input to the bladder through the release of acetylcholine, which acts on muscarinic receptors (primarily M3) in the detrusor muscle to trigger contraction.4 Simultaneously, inhibition of sympathetic activity (which normally maintains urethral tone) and somatic activity to the external urethral sphincter allows the urethra to relax, creating a pathway for urine flow.5 This coordination is orchestrated by the pontine micturition center in the brainstem, with higher cortical centers providing voluntary control over the process.6
Problems with bladder emptying can lead to urinary retention, a condition where urine cannot be completely expelled from the bladder, resulting in residual urine that increases the risk of urinary tract infections, bladder damage, and kidney complications.7
Clinical Context
Bladder emptying dysfunction is a significant clinical concern that affects approximately 10% of men over age 70 and up to 30% of men over 80, with lower prevalence in women.1 Problems with bladder emptying can manifest as acute (sudden) or chronic (gradual) urinary retention, which is the inability to completely void urine from the bladder.2
The causes of bladder emptying problems can be categorized into several groups:
Obstructive causes include benign prostatic hyperplasia (BPH), which is the most common cause in older men, urethral strictures, bladder stones, tumors, and in women, cystocele or rectocele.3 These physical obstructions prevent the normal flow of urine through the urethra despite proper bladder contraction.
Neurogenic causes involve disruption of the neural pathways controlling micturition and include conditions such as stroke, multiple sclerosis, Parkinson’s disease, diabetic neuropathy, and spinal cord injuries.4 These conditions can affect either the afferent (sensory) pathways that detect bladder fullness or the efferent (motor) pathways that control muscle contraction and relaxation.
Medication-related causes are common and include anticholinergics, antidepressants (particularly tricyclics), antihistamines, opioids, and muscle relaxants.5 These medications can interfere with the normal neural control of bladder function, often by blocking the action of acetylcholine on muscarinic receptors in the detrusor muscle.
Other factors include post-surgical effects (particularly after pelvic or spinal surgery), infections or inflammation of the urinary tract, and weakened bladder muscles due to aging or chronic overdistension.6
Diagnosis of bladder emptying problems typically involves measuring post-void residual urine volume, urodynamic testing to assess bladder and urethral function, cystoscopy to visualize the bladder and urethra, and imaging studies.7 Treatment approaches depend on the underlying cause and may include catheterization (intermittent or indwelling), medications (such as alpha-blockers for BPH), surgery to relieve obstruction, neuromodulation for neurogenic causes, and behavioral techniques.8
Complications of untreated bladder emptying problems include recurrent urinary tract infections, bladder damage from chronic overdistension, kidney damage due to backflow of urine, overflow incontinence, and bladder stones.9 Early diagnosis and appropriate management are essential to prevent these complications and improve quality of life.