How to manage urinary symptoms in patients with myasthenia gravis?

Management of Urinary Symptoms in Myasthenia Gravis

Patients with myasthenia gravis (MG) have significantly more lower urinary tract symptoms (LUTS), particularly overactive bladder symptoms, than healthy individuals, and these symptoms should be actively managed to improve quality of life.

Understanding Urinary Symptoms in MG

Urinary symptoms in MG patients are common and can significantly impact quality of life. Research shows:

• MG patients have higher rates of daytime frequency (43%), nocturia (24%), and urinary incontinence (43%) compared to healthy controls 1
• Symptoms are often related to:
  • Disease-related autonomic dysfunction
  • Medication side effects, particularly from acetylcholinesterase inhibitors
  • Potential involvement of muscarinic acetylcholine receptors in smooth muscle

Assessment of Urinary Symptoms

Initial Evaluation

1. Medication review:

   • Assess current pyridostigmine dosage (doses >300mg daily correlate with higher overactive bladder scores) 2
   • Review other medications that may affect bladder function

2. Urinalysis:

   • Rule out urinary tract infection or microhematuria
   • If microhematuria is present, follow AUA guidelines for risk stratification 3

3. Post-void residual (PVR) assessment:

   • Essential for patients with MG to evaluate for urinary retention 3
   • Critical for those with neurological conditions to prevent upper tract complications

4. Consider urodynamic studies:

   • Complex cystometrogram (CMG) to distinguish between detrusor overactivity and other bladder dysfunction
   • Pressure flow studies to differentiate between bladder outlet obstruction and detrusor hypocontractility 3

Management Algorithm

Step 1: Optimize MG Treatment

• Adjust pyridostigmine dosing:
  • Use lowest effective dose to control MG symptoms while minimizing cholinergic side effects on bladder 2
  • Target maximum of 120mg orally four times daily 4
  • Consider dose reduction if urinary symptoms are prominent and MG is well-controlled

Step 2: Manage Overactive Bladder Symptoms

For patients with frequency, urgency, and urge incontinence:

• Behavioral modifications:

  • Timed voiding
  • Fluid management
  • Pelvic floor exercises

• Pharmacotherapy options:

  • Use with caution: Anticholinergics may worsen myasthenic weakness
  • Consider: Beta-3 adrenergic agonists (mirabegron) as they have fewer anticholinergic effects
  • Monitor: For worsening of MG symptoms with any medication

Step 3: Manage Urinary Retention

For patients with elevated PVR or retention:

• Avoid distigmine bromide:

  • Can cause severe cholinergic crisis even at therapeutic doses 5

• Consider intermittent catheterization for patients with significant retention

Step 4: Special Considerations

• Surgical interventions:

  • If prostatectomy is required in male MG patients, open surgery is preferred over transurethral resection to reduce risk of post-operative incontinence 6
  • If TURP is necessary, high-frequency current with careful resection at the prostatic apex is recommended 6

• For refractory symptoms:

  • Consider referral to urology for specialized management
  • Evaluate for concomitant neurological or urological conditions

Monitoring and Follow-up

• Regular reassessment of urinary symptoms with treatment adjustments
• Monitor for upper urinary tract complications in patients with significant retention
• Reassess after any changes in MG treatment regimen

Important Pitfalls to Avoid

1. Don't assume urinary symptoms are solely medication side effects - they may be part of the disease process itself involving muscarinic receptors 7

2. Don't overlook the impact of urinary symptoms on quality of life - LUTS-related QOL is significantly worse in MG patients 1

3. Avoid medications that can exacerbate both MG and urinary symptoms - careful medication selection is essential

4. Don't miss concurrent urological conditions - perform appropriate risk-based evaluation for microhematuria or other urological findings 3

By systematically addressing urinary symptoms in MG patients with this approach, clinicians can significantly improve quality of life while maintaining optimal management of the underlying myasthenia gravis.