Why does my bladder exhibit hyperreflexic urgency while the sensation of filling is muted after a straining injury three years ago and a fistulotomy seven months ago?

Understanding Your Bladder Dysfunction: Hyperreflexic Urgency with Muted Filling Sensation

What Is Happening in Your Bladder

Your bladder exhibits detrusor overactivity (the "hyperreflexic urgency") while simultaneously having impaired sensory signaling (the "muted" filling sensation)—a paradoxical pattern called "detrusor overactivity with impaired contractility." 1

This creates a confusing clinical picture where:

• The urgency comes from involuntary detrusor contractions that occur unpredictably during bladder filling, generating sudden, compelling urges to void that are difficult to defer 2, 3
• The muted filling sensation results from impaired sensory feedback from your bladder wall, meaning you don't get the normal, gradual awareness of bladder volume that healthy people experience 2, 1
• Your post-void residual remains normal (likely under 250-300 mL), indicating you're emptying adequately despite the sensory deficit 1

Why This Paradox Occurs

The Dual Mechanism

Detrusor overactivity generates urgency through involuntary muscle contractions, while impaired contractility simultaneously diminishes the normal sensory feedback that conveys filling awareness. 1

• The involuntary contractions trigger sudden urgency episodes and urge incontinence 1
• The impaired contractility blunts your ability to sense gradual bladder filling 1
• You may store larger bladder volumes without usual filling cues, then experience sudden urgency when an involuntary contraction occurs 1

Contributing Factors from Your History

Pelvic floor hypertonicity—likely from your straining injury and fistulotomy—generates additional afferent input through increased muscle tension that independently triggers or amplifies urgency sensations. 2

• This hypertonicity creates extra proprioceptive signaling that antimuscarinics cannot address 2
• The pelvic floor dysfunction may be perpetuating both the urgency and the altered sensory perception 2

The Role of Antimuscarinic Therapy

If you're taking anticholinergic medications (like oxybutynin), they block muscarinic M3 receptors in your bladder wall, which simultaneously reduces involuntary contractions (therapeutic goal) AND further blunts sensory signaling that conveys normal filling awareness. 1

This explains why:

• Your urgency may persist despite medication (incomplete suppression of detrusor overactivity or additional pathology beyond simple overactivity) 2
• Your filling sensation feels even more muted (the medication dampens both motor and sensory pathways) 1, 4

Clinical Management Strategy

Dual-Targeted Approach Required

Continue bladder-directed anticholinergic treatment while adding pelvic floor physical therapy to address the hypertonicity component that antimuscarinics cannot affect. 2

Key interventions:

• Scheduled voiding regimen (every 3-4 hours while awake) rather than relying on urge cues, since your bladder sensation is blunted 1
• Pelvic floor muscle training to reduce hypertonicity-related afferent signaling that contributes to urgency 2, 3
• Behavioral therapies including fluid management, caffeine reduction, and bladder training 3
• Periodic post-void residual monitoring to ensure values remain below 250-300 mL, confirming the sensory blunting isn't causing retention 1

When to Escalate

If urgency persists after optimizing anticholinergic dosing and completing pelvic floor therapy, urodynamic testing should be performed to verify whether detrusor overactivity is adequately suppressed or to identify alternative diagnoses such as bladder hypersensitivity without detrusor overactivity. 2

Common Pitfalls to Avoid

• Don't rely solely on sensation to trigger voiding—your impaired filling awareness means you need a time-based schedule 1
• Don't assume antimuscarinics alone will resolve urgency—the pelvic floor hypertonicity requires physical therapy 2
• Don't ignore the scheduled voiding regimen—storing larger volumes without cues increases risk of sudden urgency episodes 1

The Bottom Line

Your bladder has two simultaneous problems: overactive muscle contractions causing urgency, and impaired sensory nerves causing muted filling sensation. The straining injury and fistulotomy likely created pelvic floor hypertonicity that perpetuates both issues. Treatment requires addressing both the bladder muscle (with medications) and the pelvic floor (with physical therapy), while using scheduled voiding to compensate for your blunted sensation. 2, 1