Functional Urology

Physiology and Classification

Storage and voiding depend on a coordinated reflex network from the bladder wall up to the brain. Understanding the anatomy, the autonomic/somatic innervation, and the reflexes that switch between storage and voiding is the foundation for classifying every lower-urinary-tract (LUT) dysfunction as a failure to store or a failure to empty, due to the bladder or the outlet.

Lower Urinary Tract Anatomy

• Bladder layers:
  • Urothelium (~7 cells thick) — functions: (1) a relatively impermeable barrier (uroplakin and tight-junction proteins); (2) sentinel defense against uropathogens (uroplakins are the attachment site for type-1 piliated E. coli); (3) afferent signaling (urothelial cells release/respond to neurotransmitters via myofibroblasts); and (4) modulation of detrusor contractility. The glycosaminoglycan layer may aid bacterial anti-adherence but has no proven impermeability role.
  • Lamina propria — a plexus of unmyelinated nerves, interstitial cells (myofibroblasts), and microvasculature.
  • Detrusor — fascicles in random directions; gap junctions let excitation propagate through the smooth-muscle syncytium; has afferent innervation; contractility declines rapidly with ischemia.
• Internal (smooth) sphincter — a competent ring at the bladder neck in males (absent in females); a physiologic, not anatomic, sphincter, not under voluntary control.
• External (striated) sphincter (EUS): under voluntary control, innervated by the pudendal nerve (S2–S4), with slow-twitch fibers (sustained tone) and fast-twitch fibers (rapid tone for sudden pressure rises). Two parts: the periurethral pelvic-floor striated muscle (both fiber types; pelvic-floor exercises may convert fast- to slow-twitch) and the rhabdosphincter (predominantly slow-twitch, in the outer wall of the proximal urethra).

Smooth Muscle and Bladder Mechanics

• Contraction: parasympathetic acetylcholine acts on muscarinic receptors → Ca²⁺ entry → Ca²⁺-calmodulin activates myosin light-chain kinase → actin–myosin interaction; relaxation when intracellular Ca²⁺ falls. Interstitial cells/myofibroblasts may pace spontaneous activity.
• Storage (filling): compliance = ΔV/ΔP. Decreased compliance results from (1) viscoelastic changes — more collagen/less elastin (from injury, obstruction, denervation; once collagen-replaced, it is unresponsive to drugs/distention/nerve section and often needs augmentation), fast filling rate (slow physiologic filling keeps Pves <10 cm H₂O), and detrusor hyperactivity; or (2) central neural input. Types I, III, IV collagen predominate; type III especially associates with poor storage.
• Voiding: Pdet = Pves − Pabd. Low voiding pressure in women does not necessarily mean impaired contractility.

Neural Control

Micturition uses three nerves, all carrying efferent and afferent fibers: parasympathetic (pelvic, S2–S4), sympathetic (hypogastric, T11–L2), and somatic (pudendal, S2–S4).

• Parasympathetic (sacral S2–S4) — contributes to voiding: excites the bladder and relaxes the urethra. Cauda equina/pelvic plexus injury causes decentralization (not complete denervation).
• Sympathetic (T11–L2) — contributes to storage: relaxes the bladder (β-adrenergic), contracts the bladder base and urethra (α-adrenergic).
• Somatic (pudendal, S2–S4; motoneurons in the Onuf nucleus) — contributes to storage: contracts the EUS.

Afferents:

Fiber type	Location	Normal function	Effect of inflammation
Aδ (finely myelinated)	Smooth muscle	Sense bladder fullness (wall tension)	Discharge at lower pressure threshold
C fiber (unmyelinated)	Mucosa	Stretch/volume sensing	Discharge at lower threshold
C fiber (unmyelinated)	Mucosa/muscle	Nociception to overdistention; silent afferent	Sensitive to irritants; becomes mechanosensitive, unmasking a new afferent pathway

Pelvic-nerve afferents are most important for normal micturition. Modulators of afferent sensitivity include nitric oxide (major mediator of urethral smooth-muscle relaxation; PDE5 terminates NO action) and urothelial ATP release. Aging and diabetes reduce afferent sensitivity → impaired voiding and higher residuals.

• Pontine micturition center (PMC / Barrington nucleus): the essential control center integrating afferent input and coordinating sphincter relaxation with detrusor contraction; glutamate is its primary neurotransmitter. The PMC indirectly inhibits the Onuf nucleus via GABAergic interneurons.

Reflex Circuitry

• Storage (guarding) reflex — bladder distention → low-level Aδ afferent firing → sympathetic outflow (contract bladder base/urethra, relax bladder) and pudendal outflow to the EUS; parasympathetic is inactive.
• Voiding (spinobulbospinal) reflex — high-level afferent activity activates the PMC, which inhibits the guarding reflex and stimulates parasympathetic outflow (contract bladder, relax internal sphincter). The ascending signal travels pelvic nerve → periaqueductal gray → PMC → descending output. The reflex functions as an on/off switch; without higher control (infants, neuropathic bladder), involuntary emptying occurs at a critical volume.
• Emptying phase: initial urethral-sphincter relaxation (NO-mediated + withdrawal of sympathetic input), then bladder contraction and flow.
• Duloxetine (norepinephrine/serotonin reuptake inhibitor) increases both sphincter and bladder activity — used for stress and urgency incontinence.
• After spinal cord injury, a capsaicin-sensitive C-fiber spinal reflex develops and contributes to detrusor overactivity (also in MS); the research-only ice-water test is negative in healthy bladders but positive (cannot retain) when C-fiber reflexes dominate.

Classification of LUT Dysfunction

Normal storage requires low-pressure accommodation with normal sensation, a closed outlet, and no detrusor overactivity; normal emptying requires a coordinated detrusor contraction, lowered sphincter resistance, and no anatomic obstruction. Dysfunction is classified as failure to store or failure to empty, each due to the bladder or the outlet.

• Failure to store — from bladder overactivity (involuntary contractions and/or low compliance), decreased outlet resistance, or altered sensation.
  • Bladder overactivity is most commonly seen with neurologic disease (CVA, MS, Parkinson are the top causes of urge UI via loss of suprapontine inhibition → neurogenic detrusor overactivity), BOO (BPH in men; post-anti-incontinence-surgery in women), iatrogenic radiation, aging, SUI, inflammation/irritation, and idiopathic causes. Diabetes causes NDO early and impaired emptying late.
  • Decreased outlet resistance — from damage to sphincter innervation/structure or (in women) outlet support. Intrinsic sphincter deficiency is most often iatrogenic (radical prostatectomy is the most common surgical cause in men; urethral/anti-incontinence surgery in women), plus neurologic disease, lumbosacral injury, α-antagonist/relaxant drugs, and obstetric trauma.
• Failure to empty — from bladder underactivity (reduced magnitude/coordination/duration → overflow incontinence; from lumbosacral/conus disease, diabetic/alcoholic neuropathy, radical pelvic surgery) or increased outlet resistance (more common in men; anatomic obstruction or sphincter dyssynergia).
• ICS terms: overactive detrusor (neurogenic vs idiopathic); underactive detrusor (inadequate magnitude/duration); acontractile detrusor (no contraction on UDS); areflexia (acontractility from absent neural control); dysfunctional voiding (intermittent flow from periurethral striated contraction in neurologically normal patients); detrusor sphincter dyssynergia (detrusor contraction with involuntary striated-sphincter contraction); non-relaxing urethral sphincter obstruction (usually neurologic).

Urodynamics

Urodynamics (UDS) measures the pressure–volume and pressure–flow behavior of the bladder and outlet to reproduce a patient's symptoms and identify dangerous storage. It should be performed only when it will change management; failure to record an abnormality does not exclude it.

Terminology

• Cystometrography (CMG): the bladder pressure/volume relationship during filling. Pdet = Pves − Pabd (Pves in the bladder, Pabd in the rectum/vagina — the bladder is a DIVA: Det = Ves − Abd), distinguishing a true detrusor rise from raised abdominal pressure.
• Physiologic filling rate is below the predicted maximum (body weight in kg ÷ 4).

Role and Dangerous Findings

Potentially dangerous UDS findings requiring intervention: impaired compliance; detrusor–external sphincter dyssynergia (DESD); detrusor–internal sphincter dyssynergia; detrusor leak point pressure >40 cm H₂O; high-pressure detrusor overactivity throughout filling; and poor emptying with high storage pressures. Decide in advance whether to test on or off medication (on, to assess therapeutic effect; off, to uncover a cause).

The 9 Cs of pressure-flow UDS — filling/storage: Contractions (involuntary detrusor), Compliance, Coarse sensation, Continence, Cystometric capacity; emptying: Contractility, Complete emptying, Coordination, Clinical obstruction.

Filling / Storage Phase

• Detrusor overactivity (DO): involuntary contractions during filling. Characterized as neurogenic (SCI, MS) vs idiopathic; spontaneous vs provoked; phasic (rising amplitude with volume — any phasic contraction is DO regardless of amplitude) vs terminal (a single contraction at capacity causing incontinence). Non-phasic pressure changes reflect compliance, not DO. Always interpret against symptoms; failure to demonstrate DO doesn't exclude it.
• Compliance (ΔV/ΔP, mL/cm H₂O): normal 46–124. Impaired by neurologic conditions (SCI, spina bifida — usually via ↑ outlet resistance), long-term BOO, radiation cystitis, and TB. False-positive low compliance from rapid filling; false-negative (seems better than it is) from "pop-off" mechanisms (VUR, diverticula). Absolute pressure matters most — storage pressure >40 cm H₂O harms the upper tract.
• Leak point pressures:
  • Abdominal LPP (ALPP) — the Pves at which leakage occurs from raised abdominal pressure without a detrusor contraction; a measure of sphincter strength applicable only to SUI. <60 cm H₂O suggests ISD; 60–90 equivocal; >90 little/no ISD. Current technology cannot distinguish ISD from hypermobility in women (if there is no hypermobility, SUI must be ISD regardless of ALPP).
  • Detrusor LPP (DLPP) — the lowest Pdet at which leakage occurs without raised abdominal pressure or a detrusor contraction; higher urethral resistance → higher DLPP → higher upper-tract risk. Most useful with upper-motor-neuron lesions (DO + DESD), decentralization, or low compliance. When treating impaired compliance, aim for pressure well <40 cm H₂O.

Voiding / Emptying Phase

A minimum voided volume of 150 mL is needed to assess uroflow. Pressure-flow studies identify three patterns: normal (low/normal Pdet + high/normal flow); obstruction (high Pdet + low/normal flow); and detrusor underactivity (low Pdet + low flow).

• In men: Bladder Outlet Obstruction Index (BOOI) = Pdet@Qmax − 2(Qmax) — ≥40 obstructed, 20–40 equivocal, ≤20 unobstructed. Bladder Contractility Index (BCI) = Pdet@Qmax + 5(Qmax) — >150 strong, 100–150 normal, <100 weak. ~2/3 of men with symptomatic BOO have DO, resolving in 50–67% after treating obstruction.
• In women: obstruction when Qmax ≤12 mL/s and Pdet@Qmax ≥25 cm H₂O; BOOI underestimates female obstruction (women void at lower pressures).
• Sphincter coordination: EMG activity normally decreases before a voluntary contraction. DESD (involuntary sphincter activity with the detrusor contraction) requires a neurologic lesion between the pons and sacral cord and is a risk factor for upper-tract deterioration; without a lesion it is dysfunctional voiding. Pseudodyssynergia is an EMG flare from attempted voluntary inhibition of an involuntary contraction (not true DSD).

Other Studies

• Urethral pressure profilometry — maximum urethral closure pressure (MUCP) is the maximum urethral-minus-intravesical pressure; in continent women, functional length ~3 cm and MUCP 40–60 cm H₂O.
• Video-urodynamics (VUDS) — the procedure of choice for bladder-neck dysfunction; primary bladder neck obstruction can only be diagnosed on VUDS. Useful for localizing obstruction, detecting occult incontinence, evaluating VUR, and in neuropathic dysfunction. Consider for high-risk patients (neurogenic disease, unexplained female retention, prior radical pelvic surgery/diversion/transplant, prior radiation).
• Clinical use: UDS is not very useful in pure SUI with normal emptying and demonstrable leak; it is most useful with significant urgency/UUI, emptying problems, prior SUI surgery, uncertain diagnosis, prior radiation, neurologic disease, or very severe symptoms. Significantly impaired compliance is the only absolute urodynamic indication to treat BOO. In conditions with potentially harmful storage (SCI, myelomeningocele), UDS is essential before treatment and during follow-up.

Urinary Incontinence

Continence during raised abdominal pressure depends on passive pressure transmission to the proximal urethra (compressing it against its posterior support) and the active guarding reflex. Incontinence is classified by type, and evaluation screens for transient and treatable causes before targeting the underlying mechanism.

Sphincteric Mechanisms

• Male: the internal sphincter (bladder neck to verumontanum) contributes to continence; loss of the external sphincter may not cause incontinence if the bladder neck is intact.
• Female: continence comes mainly from striated muscle bulk along the proximal/mid-urethra under tonic pudendal tone, plus pubourethral-ligament fixation and posterior musculofascial (hammock) support; the relatively weak female bladder neck makes any sphincter deficiency more likely to cause leakage.

Types of Incontinence

1. Stress (SUI) — abdominal pressure exceeds urethral pressure (mostly women; men usually post-prostatectomy).
2. Urgency (UUI) — leakage with/just before urgency.
3. Mixed (MUI) — both SUI and urgency leakage ("OAB wet"); SUI with "OAB dry" is not MUI; treat the most bothersome symptom.
4. Continuous.
5. Nocturnal enuresis — leakage during sleep (vs nocturia, which is intentionally rising); in men may signal high-pressure chronic retention with renal risk.
6. Postmicturition dribble.
7. Insensible — urethral diverticula (postvoid), ectopic ureter (continuous), overflow (small-volume frequent loss).
8. Other — coital, giggle.

Epidemiology

• Women: prevalence 25–40% (SUI 10–25% > MUI 5–20% > UUI 3–10%).
• Men: prevalence 11–34% (SUI uncommon except after radical pelvic surgery/TURP/neurologic disease; UUI/MUI more common, often from BOO/OAB); higher remission than women.

Pathophysiology of Female SUI

Loss of posterior musculofascial (hammock) urethral support causes leakage; restoring posterior support — not necessarily repositioning the urethra — restores continence. ISD (severe SUI without hypermobility, the classic "pipe-stem" urethra) is identified by ALPP <60 cm H₂O; most SUI involves some ISD. Treatments correcting hypermobility (Burch, needle suspension) are less helpful with severe ISD and limited mobility.

Risk Factors

• Both sexes: age (the strongest risk factor in men), pelvic-floor disorders, neurologic disease.
• Women: Caucasian ethnicity (African-American women have higher urethral closure pressures); pregnancy (SUI ~40% in pregnancy; Cesarean confers advantage over vaginal delivery; increasing parity raises risk); obesity (BMI >30 doubles UI risk); smoking; diabetes; oral estrogen ± progestogen (raises UI risk — topical estrogen does not and treats atrophy); caffeine (urgency/MUI); and depression.

Transient Causes — DIAPPERS

Delirium, Infection (UTI), Atrophic vaginitis/urethritis, Psychological, Pharmacologic, Excess urine production, Restricted mobility, Stool impaction.

Diagnosis and Evaluation

• History — characterize the incontinence (severity, quantity, triggers, impact) and voiding pattern; in women add obstetric/gynecologic and menopausal/HRT history.
• Exam — BMI; in women, external genitalia and estrogen status (signs of deficiency: urethral caruncle, urethral prolapse, labial adhesions), urethral mobility (Q-tip hypermobility = >30° from horizontal), and prolapse (lithotomy and standing); anal sphincter tone (S2–4).
• Labs: urinalysis (± PSA, electrolytes). Imaging not routine (VCUG for recurrent UTI/diverticulum/VUR; MRI for anatomy/prolapse).
• Supplemental evaluation when the diagnosis is unclear, with concomitant OAB, prior LUT/anti-incontinence surgery, suspected neurogenic bladder, negative stress test, abnormal urinalysis, elevated PVR, high-grade (≥stage 3) prolapse, or dysfunctional voiding.
• Tools: a 3-day voiding diary (as informative as 7-day), questionnaires (ICIQ-SF), PVR, and selective cystoscopy (urgency, hematuria, prior anti-incontinence/radiation/prolapse surgery).
• Urodynamics only when it will change management (planned invasive surgery, prior failed reconstruction, mixed/obstructive symptoms, elevated PVR, neurologic disease). Watch for cough-induced DO incontinence (mimics SUI). Occult SUI is unmasked by prolapse reduction — 11–50% of clinically continent patients develop de novo SUI after high-grade prolapse repair. The CARE trial showed concomitant Burch at sacrocolpopexy significantly reduced postop SUI (24% vs 44%).
• Pad test: a positive 24-hour test is urine loss >1.3 g (normal vaginal secretions up to ~0.3 g).
• Dye testing distinguishes urine from discharge and localizes fistulae: oral phenazopyridine colors urine orange; intravesical methylene blue stains a tampon blue with a vesico-/urethrovaginal fistula; with intravesical blue + oral phenazopyridine, orange staining = ureterovaginal, blue = bladder communication.

LUTS Pharmacology

Drug therapy for lower-urinary-tract symptoms targets the relevant receptors: antimuscarinics and β3-agonists increase storage; α-blockers, 5α-reductase inhibitors, and PDE5 inhibitors decrease outlet resistance; and a few agents target the sphincter, contractility, or urine production.

Muscarinic Physiology

Detrusor contraction occurs when acetylcholine stimulates muscarinic receptors. There are 5 subtypes (M1 cognition; M2 cardiac; M3 salivation/bowel/accommodation; M4/M5). All are present in the bladder; M2 predominates ≥3:1 over M3, but M3 is most important for contraction (Ca²⁺ influx + IP3-mediated release). In obstructed/neurogenic bladders the subtype shifts from M3 toward M2.

Antimuscarinics (Increase Storage)

• Mechanism: primarily decrease afferent (C and Aδ) activity during storage (when there is no parasympathetic input), with a lesser direct detrusor effect. They are safe in men with BOO (no change in flow, voiding pressure, or retention) — caution with large PVRs. In patients with involuntary contractions they raise volume to first DO, total capacity, and mean voided volume, and reduce urgency and contraction amplitude, without affecting leak-point pressures.
• Pharmacology: tertiary amines (oxybutynin, tolterodine, fesoterodine, solifenacin, darifenacin) cross the BBB (high lipophilicity, small size, low charge increase penetration); quaternary amines (trospium, propantheline) penetrate the CNS minimally. Many are CYP2D6/3A4 metabolized (drug-interaction risk).
• Contraindications: untreated narrow-angle glaucoma, GI obstruction, myasthenia gravis, history of urinary retention, cognitive impairment, hypersensitivity.
• Adverse effects: dry mouth (~30% vs 8% placebo), constipation, blurred vision, CNS effects, and rarely cardiac (QT prolongation via hERG, not muscarinic). Longest persistence reported with solifenacin.

Agent	Notable features
Oxybutynin	Antimuscarinic + direct relaxant + local anesthetic; metabolite N-desethyloxybutynin causes dry mouth (transdermal reduces it); may impair cognition (elderly, children)
Tolterodine	Bladder-selective; active metabolite 5-HMT; low cognitive effect; no QT effect
Fesoterodine	Prodrug → 5-HMT; 4/8 mg (8 mg more effective, more dry mouth)
Darifenacin	Relatively M3-selective; no effect on cognition, QT, or heart rate; no nocturia benefit
Solifenacin	Modest M3 selectivity; reduces nocturia; no cognitive/HR effect (30 mg may prolong QT)
Trospium	Quaternary amine, renally excreted, not CYP-metabolized; reduces nocturia; no cognitive effect
Propiverine	Antimuscarinic + calcium-antagonist; available in Canada (not US at time of writing)

β3-Adrenoreceptor Agonists

Mirabegron stimulates β3 receptors (the most expressed β-AR subtype in the bladder) → adenylyl cyclase → cAMP → detrusor relaxation, and inhibits afferent activity. It improves capacity/frequency/urgency/incontinence without affecting flow or PVR. Contraindicated with severe uncontrolled hypertension (SBP ≥180 or DBP ≥110), pregnancy, or hypersensitivity; CYP-mediated drug interactions; small reversible rises in BP/HR (monitor); no QT effect.

Toxins

• Botulinum toxin (onabotulinumtoxinA/Botox; abobotulinumtoxinA/Dysport): from Clostridium botulinum (subtype A has the longest action). Mechanisms: cleaves SNAP-25 → blocks acetylcholine release → paralysis (recovers in 2–4 months), terminal axonal degeneration, blocks other transmitters (ATP, substance P), and reduces afferent activity. Effective in neurogenic and idiopathic DO and OAB. Dose: 200 U for neurogenic OAB; 100 U (off-label) for idiopathic OAB. Contraindicated with active UTI, retention, inability/unwillingness to catheterize, or hypersensitivity. Adverse effects: bladder pain, hematuria, UTI; most serious is urinary retention requiring CIC (~5–6%); avoid aminoglycosides during treatment.
• Vanilloids (capsaicin, resiniferatoxin): RTX is ~1000× more potent than capsaicin for desensitization; not commonly used.

Increasing Outlet Resistance (for SUI)

• Imipramine (TCA) — anticholinergic + serotonin/noradrenaline reuptake blockade; the only agent widely used for storage symptoms despite limited RCT support; effective for childhood nocturnal enuresis. Contraindicated with MAOIs; serious cardiovascular toxicity and QTc prolongation (children especially sensitive); taper to stop.
• Duloxetine (SNRI) — improves SUI storage symptoms; licensed in the EU for moderate–severe female SUI but withdrawn from the US SUI process.
• α-agonists (ephedrine) — largely abandoned (phenylpropanolamine raised stroke risk in women). There is currently no effective drug for male SUI.
• Estrogens — oral estrogen ± progestogen worsens UI; vaginal estrogen treats urogenital atrophy/OAB symptoms but is not effective for SUI.

Facilitating Bladder Emptying

• α1-blockers reduce smooth-muscle tone at the bladder outlet and prostate. The α1A subtype mediates prostatic/urethral contraction; α1D blockade improves storage symptoms. Non-selective (TAD): terazosin, alfuzosin, doxazosin; selective: silodosin (most selective), tamsulosin, naftopidil. Effective for storage and voiding symptoms in BOO; ineffective (and may cause SUI) for female OAB. Adverse effects: dizziness (most common; highest with terazosin/doxazosin), orthostatic hypotension, headache, nasal congestion, and retrograde/ejaculatory dysfunction (silodosin 14% > tamsulosin 2%). Cautions: planned cataract surgery (intraoperative floppy iris syndrome — tamsulosin highest risk, 40× alfuzosin; hold 4–7 days preop but risk persists), multiple antihypertensives/orthostasis (prefer silodosin), and concomitant PDE5 (sildenafil/vardenafil potentiate terazosin/doxazosin hypotension; tamsulosin 0.4 mg does not).
• 5α-reductase inhibitors convert testosterone to DHT — finasteride inhibits type 2; dutasteride inhibits types 1 and 2. The Finasteride Study Group (Gormley 1992): 5 mg reduced symptoms, prostate size (~19%), and PSA (~50%). Adverse effects: reduced ejaculate volume (~4%), ED (4%), reduced libido (3%), gynecomastia (2%). Other benefits: improved PSA/DRE sensitivity for cancer detection, reduced prostatitis, and reduced risk of retention and BPH surgery.
• Striated sphincter: no drug selectively relaxes it; botulinum toxin is used (e.g. neurologic sphincter dyssynergia).
• Contractility: no effective drug for underactive bladder; bethanechol has little proven efficacy.
• PDE5 inhibitors: monotherapy improves IPSS and IIEF but not Qmax; combined with an α-blocker, improves IPSS, IIEF, and Qmax. Only tadalafil is approved for LUTS/BPH.
• Phytotherapy: saw palmetto showed no benefit over placebo (Bent 2006).

Other Agents

• Desmopressin — a vasopressin analogue (V2-receptor water reabsorption); fast onset, used for nocturia/nocturnal polyuria and childhood enuresis (suppresses but does not cure; combine with an alarm). Main risk: hyponatremia (risk factors: increasing age, female sex, cardiac disease, high 24-h urine volume). Females are more sensitive — 25 μg MELT for females, 50–100 μg for males; check serum sodium at baseline, ~day 7, ~day 30, then every 6 months. Contraindicated with type IIB/platelet-type vWD, impaired water excretion (hyponatremia, severe liver/renal/cardiac disease, polydipsia), or sodium-losing states.
• Phenazopyridine (Pyridium): urinary analgesic; ≤2 days when used with a UTI antibiotic; causes orange urine/skin discoloration; rare methemoglobinemia.
• Others: DMSO (intravesical, for interstitial cystitis), baclofen (GABA-B; poor DO efficacy), and calcium antagonists/potassium-channel openers (no bladder selectivity).

Combinations

• α-blocker + 5-ARI — MTOPS (n=3047): combination reduced clinical progression (1.5/100 person-years) more than doxazosin (2.7) or finasteride (2.9) alone (placebo 4.5). CombAT (n=4844, prostate ≥30 g): combination beat tamsulosin (but not dutasteride) for AUR/BPH surgery, and beat both monotherapies for clinical progression and symptoms at 4 years.
• α-blocker + antimuscarinic — better than an α-blocker alone in men with OAB + BOO.
• β3-agonist + antimuscarinic — mirabegron + solifenacin beats solifenacin alone without the added anticholinergic burden.

Overactive Bladder

Overactive bladder (OAB) is a symptom syndrome — urinary urgency, usually with frequency and nocturia, with or without urgency incontinence, in the absence of infection or obvious pathology — and is distinct from detrusor overactivity (a urodynamic observation).

Definitions and Pathophysiology

• Urgency is a sudden compelling, hard-to-defer desire to void; UUI is leakage with/just before urgency. OAB can coexist with SUI; SUI with "OAB dry" is not MUI.
• Three pathophysiologic hypotheses: neurogenic (loss of inhibition / re-emergence of primitive reflexes / afferent sensitization), myogenic (increased spontaneous excitation and propagation), and integrative (local contractions spreading via various routes).

Epidemiology

Prevalence ~12% (EPIC). Both sexes are similar, but men have more "OAB dry" and women more "OAB wet." Storage LUTS impact quality of life more than other LUTS.

Diagnosis and Evaluation

The 2017 CUA OAB guideline mandates four steps: history/physical, urinalysis, a questionnaire, and a voiding diary (the frequency-volume chart is the principal objective tool for frequency/nocturia). Screen for occult neurologic disease (new OAB with ED/tremor). Bladder pain syndrome is distinguished by pain (urgency in OAB does not include pain), pain rising with filling, more consistent voided volumes, and the ability to defer voiding.

Management

• Observation is acceptable once conditions requiring treatment are excluded.
• Conservative (≥6 weeks, ideally 3 months): weight loss, smoking cessation, reduced caffeine/fluid/alcohol, pelvic-floor training, and bladder retraining.
• Pharmacologic: an antimuscarinic if no contraindication (avoid in narrow-angle glaucoma, impaired gastric emptying, history of retention; consider cognition) — try at least two antimuscarinics for ≥4 weeks each; then mirabegron if antimuscarinics fail/aren't tolerated. Acute retention in men on antimuscarinics ± an α-blocker is up to 3%.
• Third-line/surgical (after confirming DO on UDS if needed): intradetrusor onabotulinumtoxinA, sacral neuromodulation, or percutaneous tibial nerve stimulation; augmentation cystoplasty is no longer recommended in adults. Two main UDS diagnoses associate with OAB — DO and increased filling sensation — though DO may be absent (especially in women) and present in asymptomatic patients.

LUTS / BPH

Benign prostatic hyperplasia (BPH) is a histologic diagnosis that can produce benign prostatic enlargement → obstruction → lower-urinary-tract symptoms. The 2021 AUA guideline structures evaluation and a stepwise ladder from behavioral measures through medical therapy to a range of surgical options chosen largely by prostate size.

Background and Evaluation

• BPH → BPE → BPO: not every man with BPH develops enlargement, and not every man with enlargement develops obstruction; long-standing obstruction can cause hydroureteronephrosis and renal insufficiency. BPH requires testosterone (5α-reductase → DHT drives growth). BPE contributes to LUTS by a static (bulk) and a dynamic (smooth-muscle tone) component. Prevalence rises with age (~60% at 60, ~80% at 80).
• Recommended initial evaluation: history/physical, urinalysis, and IPSS (AUA-SI: 7 symptoms scored 0–5 + a QoL question; 0–7 mild, 8–19 moderate, 20–35 severe). The single most important history item is the patient's motivation for treatment. Optional: PVR (>300 mL worth monitoring; weak correlation with obstruction), uroflowmetry (≥150 cc voided; Qmax <10 mL/s has 70% specificity for BOO), and urodynamics (the most complete way to confirm BOO; consider with diagnostic uncertainty or catheter-dependent retention with a possibly underactive detrusor).

Medical Therapy

• Lifestyle/behavioral (first-line): limit fluids before bed/travel, caffeine/alcohol, and bladder irritants; avoid constipation; weight loss; timed and double voiding; pelvic-floor training.
• α-blockers (alfuzosin, doxazosin, silodosin, tamsulosin, terazosin) — all roughly equally effective (IPSS improvement 4–7 points). Switch for side effects, not for insufficient response. Avoid silodosin/tamsulosin in younger sexually active men (ejaculatory dysfunction; most with silodosin); prefer alfuzosin/tamsulosin/silodosin for orthostatic-hypotension risk; counsel re: IFIS and PDE5 interactions. For acute retention from BPH, start an α-blocker and complete ≥3 days before a voiding trial.
• 5-ARIs — finasteride (type 2; serum DHT ~70%) vs dutasteride (types 1+2; ~95%); reduce prostate size 15–25%, halve PSA (double the measured value after 1 year), and improve IPSS 3–4 points. Indicated to improve LUTS in demonstrably enlarged prostates (>30 cc, PSA >1.5 ng/dL, or palpable enlargement), to reduce progression/retention/surgery (PLESS), and for prostatic bleeding. Counsel on sexual side effects and the controversial association with prostate-cancer grade; slower onset than α-blockers.
• PDE5 (tadalafil 5 mg daily) — for LUTS/BPH irrespective of ED (IPSS ↓ ~1.7 points; no urodynamic improvement; do not combine with an α-blocker — no added benefit).
• Combinations: α-blocker + 5-ARI only for demonstrable enlargement (MTOPS/CombAT); α-blocker + antimuscarinic or + β3-agonist for predominant storage symptoms (monitor PVR; β3-agonist preferable in older patients where anticholinergics are avoided).
• Follow-up at 4–12 weeks (4 weeks for α-blockers/PDE5/β3/anticholinergics; 3–6 months for 5-ARIs) with AE review and IPSS.

Surgical Therapy

Indications: symptoms refractory to or intolerant of medical therapy, or complications — refractory retention, recurrent UTI, recurrent bladder stones, recalcitrant gross hematuria, renal insufficiency (GFR <60 for ≥3 months), or progressive bladder dysfunction. An asymptomatic diverticulum or elevated PVR alone is not an indication. Preoperatively, assess PVR (recommended) and consider prostate size/shape, uroflow, pressure-flow studies, and PSA; counsel on treatment failure and sexual (ejaculatory) side effects.

• TURP — the historical standard. Bipolar uses 0.9% saline (eliminating TUR syndrome) and allows longer resection for larger glands; monopolar uses iso-osmolar glycine/sorbitol/mannitol.
• TUIP — for prostates ≤30 cc; preserves ejaculation; higher retreatment than TURP.
• Photoselective vaporization (PVP/GreenLight) — 532 nm laser absorbed by hemoglobin (penetration 0.8 mm); saline irrigation; use 120 W or 180 W platforms.
• Simple prostatectomy (open/lap/robotic) — for large–very large glands.
• Prostatic urethral lift (UroLift) — transprostatic implants widen the lumen without ablation; for 30–80 cc prostates without an obstructive middle lobe; preserves erectile/ejaculatory function; no PSA change.
• Water vapor thermal therapy (Rezum) — convective steam ablates the transition zone; for 30–80 cc; preserves sexual function.
• Laser enucleation (HoLEP/ThuLEP) — prostate-size-independent; outcomes similar to TURP.
• Others: transurethral vaporization (bipolar TUVP), microwave therapy (TUMT; higher retreatment), aquablation/robotic waterjet (30–80 cc, general anesthesia). Not recommended: transurethral needle ablation and prostate-artery embolization (outside trials).

Prostate size	Surgical options
Small (<30 g)	TUIP, TURP, PVP, TUVP, TUMT, laser enucleation
Average (30–80 g)	TURP, PVP, TUVP, TUMT, laser enucleation, WVTT, RWT, PUL
Large (>80–150 g) / very large (>150 g)	Simple prostatectomy, laser enucleation

Sexual-function preservation: PUL and WVTT are preferred. Bleeding risk: PVP and laser enucleation are preferred (laser if anticoagulation cannot be stopped).

Nocturia

Nocturia is voiding that is preceded and followed by sleep; ≥2 voids/night is clinically significant. It is associated with decreased survival and quality of life, poor sleep efficiency, depression, metabolic syndrome, and falls. A voiding diary classifies it into nocturnal polyuria, decreased bladder capacity, or global polyuria.

Diagnosis and Evaluation

• History — nocturia may signal systemic illness (hypertension, diabetes, heart/kidney disease). Drugs causing it include those raising urine output (SSRIs, tetracyclines, calcium-channel blockers, lithium, and mistimed diuretics — give mid-afternoon), CNS stimulants/insomnia-causing agents, and direct bladder toxins (ketamine, cyclophosphamide).
• Exam — peripheral edema (cardiac, nephrotic, venous) and obesity/short neck (possible obstructive sleep apnea).
• Voiding diary is the most useful tool.

Nocturnal Polyuria

Defined as nocturnal urine volume >20–33% of the 24-h total (age-dependent: ~14% at <25, ~34% at >65), >6.4 mL/kg, or >54 mL/hr.

• Causes: diuretics (timing), congestive heart failure, obstructive sleep apnea (hypoxia → ↑ ANP → ↑ sodium/water excretion; a common cause), diabetes mellitus, excessive nighttime fluids, and peripheral edema.
• Management: treat comorbidities (CPAP for OSA can improve nocturia); conservative measures (stop fluids 4 h before bed, compression stockings, mid-afternoon diuretics); and medical therapy — desmopressin (bedtime V2 antidiuresis; hyponatremia risk <1% at age <65 vs 8% at >65; melt dose 50 μg males, 25 μg females; monitor sodium baseline, day 7, day 28, then q6 months) or imipramine (use cautiously — arrhythmia, QTc prolongation, rare sudden death).

Decreased Bladder Capacity

Nocturnal urine volume exceeds nocturnal bladder capacity. The Nocturnal Bladder Capacity Index (NBCi) = actual nightly voids − predicted nightly voids, where predicted = (Nocturia Index − 1) and Nocturia Index = nocturnal urine volume ÷ maximum voided volume; NBCi >0 indicates a small nocturnal capacity. Causes (11) include stones, cystitis (bacterial/interstitial/TB/radiation), cancer, BOO, neurogenic bladder, low compliance, medications (xanthines, β-blockers), idiopathic nocturnal DO, anxiety, and learned voiding dysfunction. Management targets the cause; TURP is superior to tamsulosin for BPH-related nocturia.

Global Polyuria

24-h output >40 mL/kg causing both daytime frequency and nocturia. Causes: primary polydipsia, diabetes mellitus, and diabetes insipidus (central — ADH deficiency from hypothalamic/pituitary injury; nephrogenic — normal ADH but unresponsive kidneys).

Neurogenic LUT Dysfunction

Neurogenic lower-urinary-tract dysfunction is classified by lesion location, which predicts the storage/emptying pattern. The overriding management goal is low-pressure storage and emptying to protect the upper tracts.

Classification by Lesion Location

Lesion	History	PVR	Urodynamics	Sphincter
Suprapontine	Predominantly storage	Insignificant	Detrusor overactivity	Normal (synergic)
Spinal (infrapontine–suprasacral)	Storage + voiding	Usually elevated	DO + DSD (lesions above T6 may have autonomic dysreflexia and smooth-sphincter dyssynergia)	Overactive
Sacral / infrasacral (below S2)	Predominantly voiding	Usually elevated	Underactive/acontractile detrusor	Normal or underactive

Suprapontine lesions give DO with coordinated (synergic) sphincters; complete suprasacral cord lesions give DO with striated-sphincter dyssynergia; sacral lesions give detrusor areflexia with a fixed, non-voluntary striated sphincter tone.

Diseases at or Above the Brainstem

• CVA — acute retention (areflexia) initially; the most common long-term pattern is phasic detrusor overactivity with intact sensation and a synergic sphincter (no true DSD); UI within 7 days of stroke predicts poor outcome. Manage by reducing contractility and increasing capacity.
• Dementia — usually incontinence; antimuscarinics may be contraindicated in Alzheimer's (cortical cholinergic loss).
• Traumatic brain injury / brain tumor — usually DO with synergic sphincters (retention with frontal/posterior-fossa lesions).
• Cerebellar ataxia / normal-pressure hydrocephalus / cerebral palsy — usually DO with synergy (most CP patients have normal control).
• Parkinson disease — LUT dysfunction in 35–70%; DO is the most common UDS finding, smooth sphincter synergic; pseudodyssynergia/bradykinesia can mimic DSD; areflexia is uncommon; TURP is not contraindicated but warrants caution and full UDS.
• Multiple system atrophy (MSA) — earlier, more severe bladder symptoms with erectile dysfunction; DO common; VUDS shows an open bladder neck (unlike PD) and striated-sphincter denervation; both sphincters often insufficient → avoid outlet-reducing procedures in males.

Diseases Primarily Involving the Spinal Cord

• Multiple sclerosis — 2× more common in women; DO is the most common UDS finding, sphincter usually synergic, striated-sphincter dyssynergia in 30–65%, impaired contractility in 12–38%; rarely causes upper-tract damage. Avoid irreversible therapies (the urodynamic picture changes over time).
• Spinal cord injury —
  • Spinal shock: acontractile/areflexic bladder with a competent bladder neck and urinary retention; usually 6–12 weeks in complete suprasacral injury (sacral SCI → persistent areflexia); resolution begins with return of the bulbocavernosus reflex. Initial UDS within 3 months; VUDS with fluoroscopy is the gold standard.
  • Suprasacral SCI: DO + striated-sphincter dyssynergia + absent sensation (lesions above T6–T8 may add smooth-sphincter dyssynergia and autonomic dysreflexia) → both storage and emptying failure.
  • Sacral SCI: detrusor areflexia, a competent non-relaxing smooth sphincter, and fixed striated tone.
  • Management: keep storage pressures low; CIC ± antimuscarinics; for indwelling drainage a suprapubic catheter is preferred over a urethral catheter (less erosion/epididymo-orchitis). Routine follow-up for high pressures, VUR, stones, and infection.
  • Autonomic dysreflexia — a potentially fatal emergency in lesions above T6–T8: an exaggerated sympathetic response to a stimulus below the lesion (commonly bladder/rectal distention) → pounding headache, hypertension, flushing/sweating above the lesion, bradycardia. Do endoscopy under spinal/monitored anesthesia; sublingual nifedipine 10–20 mg can treat or prevent it.
  • VUR (17–25%, more in suprasacral SCI) — best initial treatment is to normalize urodynamics; UTI — treat only symptomatic disease; bladder cancer (SCC) is strongly associated with long-term indwelling catheters.
• Transverse myelitis — acute urinary retention (areflexia) is most common; after spinal shock, DO/DSD/low compliance.
• Neurospinal dysraphism — LUT dysfunction in 90%; the typical pattern is an areflexic bladder with an open bladder neck; the main goal is to avoid high storage pressures (CIC, intradetrusor onabotulinumtoxinA; augmentation if these fail). Tethered cord syndrome — stretch-induced dysfunction; UDS improves after detethering.
• Tabes dorsalis / pernicious anemia — "sensory" bladder (loss of sensation, large PVR). Poliomyelitis — "motor" bladder (retention, areflexia, intact sensation).

Diseases Distal to the Spinal Cord

• Disk disease — the sacral cord begins at T12–L1 and ends as the cauda equina at L2; central disk prolapse (15%) can compress the cauda equina (most protrusions at L4–L5/L5–S1). DESD does not occur (infrasacral); detrusor areflexia in ~27%; cauda equina syndrome = perineal sensory loss + loss of voluntary sphincter control + an acontractile, insensate bladder. Pre-laminectomy UDS is prudent.
• Radical pelvic surgery (APR, radical hysterectomy) — pelvic-plexus injury; ~1/3 have dysfunction (impaired contractility/failure of voluntary contraction, decreased compliance, a fixed non-relaxing striated sphincter); goal is low-pressure storage with periodic emptying (often CIC for 6–12 months); avoid prostatectomy in men unless clear BOO (worsens sphincteric UI).
• Diabetes — the most common cause of peripheral neuropathy; "diabetic cystopathy" classically progresses from impaired sensation to decreased contractility, but DO is the most common recent UDS finding; sphincter dyssynergia is not typical; early timed voiding helps.
• Guillain-Barré — usually reversible dysfunction (↑ PVR, ↓ sensation, DO, ↓ compliance); manage with reversible therapy. Herpes zoster — sacral ganglion invasion → retention/areflexia, usually resolving in 1–2 months.
• Miscellaneous: SLE, schistosomal myelopathy (bladder-neck obstruction), AIDS, and TB can cause storage or voiding symptoms.

Other Conditions

• DSD — true DSD requires a lesion between the sacral cord and PMC (SCI, MS, transverse myelitis); be skeptical otherwise and distinguish from pseudodyssynergia. Untreated, >50% of men develop complications (VUR, upper-tract deterioration, stones, sepsis); treat with CIC, sphincterotomy, a stent, intrasphincteric onabotulinumtoxinA, or diversion.
• Dysfunctional voiding — involuntary striated-sphincter obstruction without neurologic disease (hard to prove; needs EMG evidence without abdominal straining).
• Bladder-neck dysfunction (smooth-sphincter dyssynergia) — incomplete bladder-neck opening, almost exclusively in young/middle-aged men with longstanding symptoms; diagnosed on VUDS; α-blockers help, and bladder-neck incision is the definitive male treatment.
• Female BOO — uncommon; from dysfunctional voiding, cystocele, prior incontinence surgery, stricture, prolapse, or diverticulum; operate cautiously (sphincteric-incontinence risk).
• Fowler syndrome — urinary retention in young women without overt neurologic disease, bladder capacity >1 L without urgency, impaired sphincter relaxation on EMG, detrusor acontractility; treat with neuromodulation.
• Postoperative retention (4–25%), radiation (early storage symptoms peaking at 4–6 weeks, usually recovering by 6 months), and the defunctionalized bladder (decreased capacity/compliance, rehabilitated by cycling).
• Aging-related changes: decreased afferent activity, efferent activity, detrusor contractility, and urethral pressure.

Goals of treating neurogenic dysfunction: preserve the upper tracts, control infection, adequate low-pressure storage and emptying, continence, no catheter/stoma, and social/vocational adaptability.

Neuromodulation

Neuromodulation uses electrical stimuli to alter neurotransmission in storage and emptying disorders — most importantly sacral neuromodulation and percutaneous tibial nerve stimulation for refractory OAB and non-obstructive retention.

Principles

Neurostimulation produces an immediate response; neuromodulation alters neurotransmission. The putative mechanism of sacral neuromodulation is activation of somatic sacral afferent inflow at the sacral root, which modulates the storage/emptying reflexes in the bladder and CNS — in OAB it modulates sensory outflow to the PMC to prevent involuntary contractions, and in retention it inhibits the guarding reflex.

Patient Selection

Neuromodulation is tried when conservative measures fail and before invasive surgery (enterocystoplasty, diversion); no UDS finding predicts response. Contraindications — absolute: significant spine/sacral anatomic abnormalities, cognitive dysfunction, physical limitations preventing pelvic-organ function, non-compliance; relative: pregnancy and MRI (older devices preclude spinal/below-head MRI; turn devices off; for elective MRI the device is often removed and replaced).

Sacral Neuromodulation (SNS)

• FDA-approved indications: non-obstructive urinary retention, urinary urge incontinence, urgency-frequency syndrome, and chronic fecal incontinence. Not FDA-approved for symptoms from known neuropathy (MS, Parkinson, SCI, pelvic-nerve injury).
• Technique (two stages): Stage I is a trial of an external lead in the S3 foramen (located ~9 cm cephalad from the sacral drop-off, 1–2 cm lateral to midline); Stage II implants the pulse generator if there is >50% improvement. Trial length: 1–2 weeks for urgency-frequency/UUI, 3–4+ weeks for retention.

Nerve root	Motor response	Sensory response
S2	Plantarflexion of the entire foot with lateral rotation; anal clamp	Leg and thigh
S3	Plantarflexion of the great toe + bellows reflex (anal wink/levator contraction)	Pulling in the rectum, scrotum, or vagina
S4	Bellows reflex only	Pulling in the rectum only

Selective Nerve Stimulation

• Percutaneous tibial nerve stimulation (PTNS) — the tibial nerve (L4–S3) modulates pelvic-floor/bladder/sphincter nerves; improves OAB similarly to antimuscarinics with a better adverse-effect profile; third-line OAB therapy (2019 AUA) for patients willing to attend frequent sessions (its main limitation); FDA-approved. AEs: stimulation discomfort and minor insertion-site bleeding.
• Pudendal and dorsal genital nerve stimulation are alternative afferent targets being studied.

OnabotulinumtoxinA vs Sacral Neuromodulation

OnabotulinumtoxinA is not ideal with emptying disorders or retention risk (if the patient won't catheterize) and needs retreatment ~every 6 months; sacral neuromodulation is less attractive in neurogenic conditions, for patients unwilling to undergo an implant, or who may need future MRIs.

Electrical Stimulation for Emptying

• Sacral rhizotomy/anterior root stimulation: S3 provides the dominant motor innervation of the bladder; posterior rhizotomy reduces reflex detrusor activity and improves compliance; the Brindley stimulator uses post-stimulus voiding (the sphincter relaxes faster than the detrusor between pulse trains).
• Sacral neuromodulation is successful for idiopathic non-obstructive retention, post-hysterectomy deafferentation retention, and Fowler syndrome.

Complications and Troubleshooting

• The most common test-stimulation complication is lead migration (12%); the most common post-implant complication is pain (15% at 12 months); surgical revision in ~33%, explant for inefficacy in ~10%; infection is managed by explanting the whole system.
• Impedance (normal 400–1500 ohms) checks integrity: open circuit (fractured lead/loose connection) → high impedance (>4000 ohms), identified on unipolar testing, no stimulation; short circuit (fluid intrusion/crushed wires) → low impedance (<50 ohms), identified on bipolar testing. For pocket vs output discomfort, turn the device off — if discomfort persists it is pocket-related.