The detrusor muscle is the smooth muscle found in the wall of the urinary bladder.
Its primary functions are to relax to allow the bladder to store urine and to contract during urination to push urine out of the bladder and into the urethra.
The detrusor muscle is composed of interwoven smooth muscle fibers oriented in longitudinal and circular layers: its multi-directional orientation allows the bladder wall to stretch significantly as it fills with urine.
The detrusor muscle is under the control of the autonomic nervous system.
During the storage phase, sympathetic nerves cause the detrusor muscle to relax while the internal urethral sphincter contracts to keep the bladder closed.
During voiding, this process reverses: the detrusor muscle contracts, and the urethral sphincters relax, allowing for the expulsion of urine.
Pathology of the detrusor muscle can lead to various urinary dysfunctions, including:
Overactive Bladder (OAB) / Detrusor Overactivity:
When the detrusor muscles contract too often or involuntarily, creating an urgent and frequent need to go to the toilet, which may lead to urge incontinence.
Overactive Bladder causes can be idiopathic, related to aging, or linked to neurological conditions like multiple sclerosis or spinal cord injury.
Underactive Bladder (UAB) / Detrusor Underactivity (DU)
This involves a contraction of reduced strength and/or duration, resulting in prolonged or incomplete emptying of the bladder.
This can lead to urinary retention and recurrent infections.
Potential causes include aging, diabetes mellitus, bladder outlet obstruction, and neurogenic issues.
Detrusor Hyperactivity with Impaired Contractility (DHIC) is a complex condition where the bladder is overactive but empties ineffectively, leading to both urgency symptoms and significant post-void residual urine.
Treatments vary depending on the specific condition and may include behavioral therapies (like Kegel exercises to strengthen pelvic floor muscles), medication, or in some cases, surgical options.