Underactive bladder

Disease Description (Causes and Symptoms)

• Definition summary: Underactive bladder (UAB) is a condition in which the contractile strength and/or duration of contraction of the detrusor muscle (the smooth muscle of the bladder) is reduced, preventing the bladder from emptying completely or sufficiently. This may result in prolonged urination or a large amount of residual urine.
• Pathophysiology: When effective detrusor contraction for urination is reduced or the outflow resistance is relatively high, residual urine can accumulate, potentially leading to bladder overdistension and progressive functional deterioration. Causes vary and include myogenic injury, neurogenic injury, surgical or traumatic factors, aging, and medication-induced causes.
• Major causes: Advanced age, diabetes and diabetic neuropathy, peripheral or central nervous system diseases (including spinal cord injury, Parkinson’s disease, and multiple sclerosis), nerve damage caused by pelvic surgery (such as colorectal or gynecologic surgery), degenerative changes in the detrusor muscle itself, and certain medications (including anticholinergics, antihistamines, opioids, and some antidepressants).
• Major symptoms: Weak urinary stream (reduced flow rate), delayed urination or hesitancy, straining to urinate (increased abdominal pressure), prolonged urination time, high residual urine volume (a feeling of incomplete emptying), recurrent urinary tract infections, and, in severe cases, overflow incontinence or worsening kidney function.

Treatment Methods

• Diagnostic evaluation: Assessment of urinary symptoms, a voiding diary (urine volume and frequency), measurement of post-void residual urine (PVR) (by ultrasound or catheterization), uroflowmetry (Qmax), and, when necessary, comprehensive urodynamic testing to evaluate detrusor contractility and bladder and urethral function. To identify the cause, blood glucose testing, neurological examination, and confirmation of a history of pelvic surgery may also be performed.
• Conservative (non-surgical) treatment
  • Behavioral therapy: Regular, scheduled urination (timed voiding), double voiding, bladder training, fluid and caffeine management, and treatment of constipation.
  • Medication therapy:
    • Medications that reduce outflow resistance (mainly when coexisting BPH is present in men): Alpha-blockers (e.g., tamsulosin) — reduce resistance in the urethra and bladder neck.
    • Detrusor stimulants (cholinergic agents, e.g., bethanechol) — should be used cautiously because of limited evidence and adverse effects (increased oral secretions, diarrhea, bronchoconstriction, etc.).
    • Anticholinergics should generally be avoided or used cautiously because they may worsen residual urine and voiding dysfunction.
  • Electrical and neuromodulation therapy: In selected patients, sacral neuromodulation may help with non-obstructive urinary retention, but the indications and effectiveness vary depending on patient selection. Peripheral nerve electrical stimulation (tibial nerve stimulation) has limited supporting evidence.
• Invasive treatment
  • When outflow resistance is the cause (e.g., severe BPH): Correct the underlying disease (medication or surgical prostate treatment, such as TURP).
  • When persistent residual urine is present and does not improve with conservative treatment: Clean intermittent catheterization (CIC) is recommended (with a relatively low risk of infection and complications). If CIC is not possible, an indwelling urethral catheter or suprapubic catheter may be considered.
  • If recurrent urinary tract infections, bladder stones, or reduced kidney function develop, treatment of the relevant complication and consultation with a specialist are necessary.
• Precautions, complications, and self-management
  • Complications: Recurrent urinary tract infections, bladder stones, irreversible deterioration of bladder function (worsening bladder contractility), upper urinary tract (kidney) damage, and worsening kidney function (in cases of high-pressure residual urine).
  • Medication side effects: Cholinergic medications (diarrhea, excessive secretions, bronchoconstriction, etc.), alpha-blockers (low blood pressure, dizziness), and others.
  • Self-management: Manage residual urine (measure and record residual urine), learn clean self-catheterization techniques, drink sufficient fluids (avoiding both excessive and insufficient intake), and prevent constipation. Regular monitoring of residual urine and kidney function (creatinine) is necessary according to the doctor’s instructions.

Checklist Before an Outpatient Visit (Including Items to Bring and Sample Questions)

• Items to bring / information to record
  • A list of all medications and supplements currently being taken (including dosage and duration of use)
  • Copies of previous test results, if available, such as recently measured PVR values, urodynamic testing, ultrasound, or prostate examinations
  • A 2–3-day voiding diary (including urination times, urine volume, and nighttime awakenings)
  • The time of symptom onset and course (whether gradual or acute), surgical history (related to the pelvis or urinary tract), and neurological symptoms (such as decreased sensation or movement disorders)
  • Underlying diseases (diabetes, neurological diseases, etc.) and test results
• Sample questions to prepare in advance for the outpatient visit
  • When did urination become uncomfortable, and did the symptoms develop suddenly or worsen gradually?
  • Is there a feeling of incomplete emptying after urination, or are there actual measurements of the residual urine volume?
  • Could any of the medications currently being taken affect urination (e.g., anticholinergics, antidepressants, pain medications, etc.)?
  • Have there recently been urinary tract infections or signs of complications such as fever or flank pain?

General Sample Questions to Ask the Doctor

• What is the suspected cause of this condition? (Is it neurogenic, myogenic, or mechanical obstruction?)
• Is urodynamic testing or any other additional testing necessary? What will the tests determine?
• Is clean intermittent catheterization (CIC) necessary for my current symptoms? If so, what are the criteria for starting and how is it performed?
• What are the expected benefits and major side effects of the prescribed medication?
• What is the long-term prognosis (the likelihood of preserving bladder and kidney function)? Can treatment improve the condition?

Examples of Condition-Specific Questions

• Regarding residual urine volume criteria: "At what residual urine volume (PVR) do you recommend clean intermittent catheterization (CIC)? (For example, a threshold of 100 mL or 200 mL.)"
• Urodynamics and diagnostic criteria: "Which findings on urodynamic testing (e.g., reduced detrusor contraction pressure or decreased Qmax) are decisive for diagnosing underactive bladder? What additional imaging or neurological tests are needed?"

(Note: The clinical significance of residual urine varies depending on the patient’s condition, symptoms, and kidney function. In general, a PVR >100–200 mL may be clinically significant, so additional evaluation and treatment should be considered.)