Detrusor Muscle Hyperactivity: Medical Terminology and Clinical Context
Yes, detrusor muscle hyperactivity does exist, and the formal medical term is "detrusor overactivity" (DO), which is defined as a urodynamic observation characterized by involuntary detrusor contractions during the bladder filling phase that may be spontaneous or provoked. 1
Standardized Medical Terminology
Detrusor overactivity is the precise urodynamic diagnosis endorsed by the International Continence Society and should be used instead of older, imprecise terms like "detrusor hyperactivity" or "detrusor instability." 1, 2
Key Distinctions in Terminology:
Detrusor overactivity (DO) is a urodynamic finding—it requires cystometry to diagnose and documents involuntary bladder contractions during filling. 1, 2
Overactive bladder syndrome (OAB) is a symptom-based clinical diagnosis defined as urgency with or without urgency incontinence, usually accompanied by frequency and nocturia, and does not require urodynamic confirmation. 1, 2
DO can be further classified as idiopathic detrusor overactivity (when no neurological cause is identified) or neurogenic detrusor overactivity (NDO) (when associated with neurological conditions like multiple sclerosis, spinal cord injury, Parkinson's disease, or stroke). 2, 3, 4
Clinical Presentations Across Patient Populations
Adults with Lower Urinary Tract Symptoms
In older men, DO is one component of lower urinary tract symptoms (LUTS) that includes both storage symptoms (urgency, frequency, nocturia) and voiding symptoms, and may coexist with bladder outlet obstruction from prostatic enlargement. 1
In women with urgency incontinence or mixed incontinence, multichannel filling cystometry can identify DO when invasive or irreversible treatments are being considered, though the absence of DO on a single study does not exclude it as a causative factor. 1
Women with high-grade pelvic organ prolapse may have occult DO that becomes apparent only when the prolapse is reduced during urodynamic testing. 1
Pediatric Populations
In children, DO may coexist with dysfunctional voiding patterns, creating mixed presentations with urgency, urge incontinence, and incomplete bladder emptying. 1
Children with overactive bladder symptoms are most commonly diagnosed with idiopathic detrusor overactivity disorder (IDOD), characterized by urgency with a short EMG lag time and quiet pelvic floor EMG during voiding. 5
Neurological Disease Populations
A wide spectrum of neurological disorders cause NDO, including Parkinsonian syndromes (18%), multiple system atrophy (18%), multiple sclerosis (18%), spinal cord lesions (15%), and multiple cerebral infarction (12%). 4
NDO in patients with multiple sclerosis or spinal cord injury frequently leads to increased storage pressures that put the upper urinary tract at risk for deterioration, making pressure reduction a primary therapeutic goal. 3
Complex Presentations: Detrusor Overactivity with Impaired Contractility
A critical pitfall to recognize: Detrusor overactivity can paradoxically coexist with detrusor underactivity, creating a condition called detrusor hyperactivity with impaired contractile function (DHIC). 1, 4
This mixed dysfunction results in episodes of urgency and urge incontinence combined with incomplete bladder emptying, as detrusor contractility is impaired and the tonic phase of voiding is not well sustained. 1
DHIC is commonly caused by neurological diseases including Parkinsonian syndromes, multiple system atrophy, progressive supranuclear palsy, multiple sclerosis, and cervical spondylotic myelopathy. 4
In children, DHIC may represent the clinical endpoint where urge incontinence leads to dysfunctional voiding, high bladder pressures, and eventual detrusor decompensation. 1
Diagnostic Approach
Urodynamic studies with multichannel filling cystometry are required to definitively diagnose detrusor overactivity, as this is a urodynamic observation, not merely a symptom. 1
Symptoms and signs should be recorded during urodynamic studies to correlate them with any involuntary contractions, as this correlation is essential for accurate diagnosis. 2
Two types of DO are recognized: phasic detrusor overactivity (which may or may not lead to incontinence) and terminal detrusor overactivity (a single involuntary contraction that often results in complete bladder emptying). 2
Common Clinical Pitfall
Most patients with OAB symptoms are treated empirically without urodynamic confirmation of DO, which is appropriate for initial conservative and pharmacological management. 2 However, when conservative treatments fail and invasive, potentially morbid, or irreversible treatments are considered (such as botulinum toxin injection, sacral neuromodulation, or surgery), urodynamic confirmation becomes important to guide therapy selection. 1