62 INCONTINENCE & ERECTILE DYSFUNCTION

# 63 INCONTINENCE & ERECTILE DYSFUNCTION

Detailed notes

Bladder anatomy and embryology

The bladder is a hollow muscular reservoir lined with transitional epithelium (urothelium). Two regions matter for the exam, because they have different origins and different behaviour.

The body of the bladder (dome and walls) is derived from the endodermal urogenital sinus — the anterior part of the cloaca after partitioning by the urorectal septum. It is lined by urothelium and powered by the detrusor, a network of interlacing smooth muscle bundles that contracts en masse during micturition.

The trigone is the smooth triangular area on the posterior wall, bounded by the two ureteric orifices superiorly and the internal urethral meatus inferiorly. It is mesodermal in origin, derived from the absorbed caudal ends of the mesonephric ducts. This is why the trigone behaves differently from the rest of the bladder — it is sensitive, non-distensible and the most common site for transitional cell carcinoma.

➡ Body of bladder = endoderm (urogenital sinus)

➡ Trigone = mesoderm (mesonephric duct remnants)

➡ Detrusor = smooth muscle of the body, contracts to void

The internal urethral sphincter is a smooth-muscle thickening at the bladder neck (involuntary). The external urethral sphincter is striated muscle in the deep perineal pouch surrounding the membranous urethra (voluntary).

👩‍⚕️ The trigone's mesodermal origin explains its dual personality: it shares innervation with the detrusor but is histologically and embryologically distinct, and it is where bladder cancers cluster.

Innervation — the only diagram that matters

Three nerve supplies act on the lower urinary tract. Get these right and most SBA questions on incontinence become trivial.

System	Roots	Effect	Phase
Parasympathetic (pelvic splanchnics)	S2–S4	Detrusor contracts, internal sphincter relaxes	Voiding
Sympathetic (hypogastric)	T11–L2	Detrusor relaxes (β3), internal sphincter contracts (α1)	Storage
Somatic (pudendal nerve)	S2–S4	External sphincter contracts (voluntary)	Continence

👩‍⚕️ Memory aid: "S2–4 keeps the floor; T11–L2 holds the urine in you." Or the classic: S2, 3, 4 keep the poo off the floor.

The micturition reflex: bladder stretch receptors fire → afferents via pelvic splanchnic nerves to S2–S4 → efferent parasympathetic outflow contracts detrusor and relaxes the internal sphincter. The brain (pontine micturition centre) coordinates voluntary relaxation of the pudendal nerve to open the external sphincter.

➡ Spinal cord transection above S2 → loss of voluntary control, but the pudendal reflex keeps the external sphincter tonically closed (reflex bladder).

➡ Cauda equina lesion below S2 → flaccid sphincter, overflow incontinence.

👩‍⚕️ Point and Shoot — Point (erection) = Parasympathetic, pelvic splanchnics, S2–4. Shoot (ejaculation) = Sympathetic, hypogastric, T11–L2. Damage during low anterior resection or radical prostatectomy classically destroys the cavernous nerves (autonomic plexus on the prostate) → erectile dysfunction.

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Benign prostatic hyperplasia (BPH)

Nodular hyperplasia of the transitional zone of the prostate (cancer favours the peripheral zone — a classic exam contrast). Incidence rises sharply with age: >50% of men by 60, >80% by 80. Driven by dihydrotestosterone (DHT), which is why 5α-reductase inhibitors help.

LUTS are categorised into three groups:

- Voiding (obstructive): hesitancy, weak/intermittent stream, straining, terminal dribbling, incomplete emptying.

- Storage (irritative): frequency, urgency, nocturia, urge incontinence.

- Post-micturition: post-void dribbling, sensation of incomplete emptying.

Investigations: IPSS score, urinalysis, U&Es, PSA (counsel first — DRE, recent ejaculation, UTI and instrumentation all raise it), post-void residual on USS, flow rate.

Management ladder:

1. Lifestyle — reduce evening fluids, caffeine, alcohol.

2. α1-blocker (e.g. tamsulosin) — relaxes prostatic smooth muscle, works within days. Side effects: postural hypotension, retrograde ejaculation, intra-operative floppy iris syndrome (warn cataract surgeons).

3. 5α-reductase inhibitor (e.g. finasteride) — shrinks the gland over 3–6 months; halves PSA (correct interpretation by doubling).

4. Surgical: TURP — gold-standard for refractory LUTS or complications (retention, stones, recurrent UTI, hydronephrosis). Open/robotic prostatectomy for very large glands.

TURP complications: bleeding, retrograde ejaculation (75%), erectile dysfunction, urethral stricture, and TUR syndrome — dilutional hyponatraemia and fluid overload from absorption of hypotonic glycine irrigation fluid through opened venous sinuses. Modern bipolar/saline systems have largely eliminated this.

👩‍⚕️ BPH is in the transitional zone; prostate cancer is in the peripheral zone. That's why DRE detects cancer (peripheral, palpable) more readily than BPH (central).

Prostate cancer

Adenocarcinoma of the peripheral zone. Risk factors: age, Afro-Caribbean ethnicity, family history, BRCA2.

Presentation: often asymptomatic and picked up on raised PSA; advanced disease presents with LUTS, haematuria, or bone pain from sclerotic metastases (vertebrae, pelvis — via Batson's venous plexus).

Diagnosis: PSA + DRE → multiparametric MRI → transperineal (or trans-rectal) USS-guided biopsy. Histology graded with the Gleason score (sum of the two most common patterns, each 1–5; ≥7 is significant).

Staging: MRI pelvis, bone scan / PSMA-PET for metastases.

Treatment depends on risk and life expectancy:

- Localised: active surveillance, radical prostatectomy, or radical radiotherapy (external beam or brachytherapy).

- Locally advanced/metastatic: androgen deprivation therapy — LHRH analogues (goserelin, leuprorelin) with an anti-androgen (bicalutamide) cover during the initial testosterone flare; bilateral orchidectomy is the surgical equivalent.

👩‍⚕️ Sclerotic bone metastases in an older man = think prostate. Lytic mets in a woman with breast lump = think breast. (Breast can be mixed, but the contrast is the classic SBA pair.)

Urinary incontinence

Type	Mechanism	Trigger	First-line management
Stress	Weak urethral sphincter / pelvic floor	Cough, sneeze, laugh, exertion	Pelvic floor exercises (3 months) → duloxetine → mid-urethral sling / colposuspension
Urge	Detrusor overactivity	Sudden urge, can't make it	Bladder training → antimuscarinic (oxybutynin, solifenacin) or β3 agonist (mirabegron) → Botox / sacral neuromodulation
Overflow	Chronic retention with leak past full bladder	Constant dribble, palpable bladder	Treat cause (BPH, neurogenic), catheterise
Mixed	Stress + urge components	Both	Treat the dominant component first
Continuous	Anatomical: vesicovaginal fistula, ectopic ureter	Constant wetness, no warning	Imaging, surgical repair

Risk factors for stress incontinence: vaginal delivery (pudendal stretch, levator damage), menopause, obesity, post-radical prostatectomy (sphincter injury — leading cause of male stress incontinence).

Investigations:

➡ Urinalysis (exclude infection, haematuria)

➡ Bladder diary (3 days)

➡ Post-void residual on USS

➡ Urodynamics — gold standard to distinguish detrusor overactivity from sphincter weakness when surgery is being considered.

👩‍⚕️ Anticholinergics treat urge incontinence but cause overflow incontinence in men with BPH by impairing detrusor contraction. A classic SBA trap.

Erectile dysfunction

The inability to achieve or maintain an erection sufficient for satisfactory sexual activity. Erection is a parasympathetic event: NO release from cavernous nerves → cGMP rise → smooth muscle relaxation of helicine arteries → engorgement of corpora cavernosa → venous outflow compressed against the tunica albuginea.

Causes:

- Vasculogenic (commonest): atherosclerosis, diabetes, hypertension, smoking. ED often precedes coronary disease by 3–5 years — treat as a cardiovascular warning sign.

- Neurogenic: post-radical prostatectomy (cavernous nerve injury), spinal cord lesions, MS, pelvic surgery, diabetic autonomic neuropathy.

- Endocrine: hypogonadism (low testosterone), hyperprolactinaemia (suppresses GnRH), thyroid disease, Cushing's.

- Drug-induced: β-blockers, thiazides, SSRIs, finasteride, antipsychotics, alcohol, opiates.

- Psychogenic: sudden onset, situational, preserved nocturnal/morning erections.

Investigations: fasting glucose/HbA1c, lipids, morning testosterone (if low → LH, FSH, prolactin), nocturnal penile tumescence if psychogenic suspected.

Treatment:

1. PDE5 inhibitors — sildenafil, tadalafil. Block cGMP breakdown → sustained erection. Absolutely contraindicated with nitrates (life-threatening hypotension) and with α-blockers given close together.

2. Vacuum erection device.

3. Intracavernosal alprostadil injection or intraurethral pellet.

4. Penile prosthesis — last resort.

👩‍⚕️ "I just took my GTN spray" + sildenafil = profound hypotension. This pairing appears in the exam.

Priapism

Painful, prolonged erection lasting >4 hours. Urological emergency in the low-flow form.

	Low-flow (ischaemic)	High-flow (non-ischaemic)
Mechanism	Venous outflow obstruction → stagnant blood, hypoxia	Unregulated arterial inflow (cavernous artery fistula)
Pain	Painful	Painless
Causes	Sickle cell, leukaemia/malignancy, intracavernosal injections, trazodone, cocaine	Perineal / penile trauma
Blood gas (corpus)	Acidotic, hypoxic	Arterial, well-oxygenated
Treatment	Emergency — aspirate corpora, intracavernosal phenylephrine, shunt	Observation, selective arterial embolisation

👩‍⚕️ Sickle cell + painful erection = low-flow priapism. Untreated >4 hours causes fibrosis of the corpora and permanent ED.

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Test yourself

A 35-year-old woman sustained urinary incontinence during obstructed labour. Which nerve roots are responsible?

• ((L4, L5::Lower limb innervation; do not supply pelvic floor.))
• ((L5, S1::Sciatic territory; not the urethral sphincter.))
• ((S1, S2::Incomplete — pudendal needs all of S2–S4.))
• ((S2, S3, S4::☑️ Pudendal nerve supplies the external urethral sphincter and pelvic floor.))

👩‍⚕️ Prolonged labour stretches the pudendal nerve as it hooks round the ischial spine.

The external urethral sphincter is innervated by which nerve?

• ((Pelvic splanchnic nerves::Parasympathetic to detrusor — not the external sphincter.))
• ((Hypogastric nerve::Sympathetic; closes internal sphincter, ejaculation.))
• ((Pudendal nerve (S2–S4)::☑️ Somatic, voluntary control of the external urethral sphincter.))
• ((Obturator nerve::Supplies thigh adductors.))

A young man with complete spinal cord transection above S2 retains some bladder continence. Why?

• ((Intact pelvic splanchnic nerves::These would empty the bladder, not retain urine.))
• ((Parasympathetic innervation of the external sphincter::The external sphincter is somatic, not parasympathetic.))
• ((Sympathetic preservation alone::T11–L2 closes the internal sphincter but cannot guarantee continence.))
• ((Intact pudendal reflex to external sphincter::☑️ Below the lesion, pudendal tone keeps the external sphincter closed.))

👩‍⚕️ Cord transection above S2 = reflex (spastic) bladder. Below S2 = flaccid bladder with overflow.

A 50-year-old woman with faecal incontinence after a prolonged labour 20 years ago. Which nerve was damaged?

• ((Pudendal nerve::☑️ Inferior rectal branch supplies the external anal sphincter.))
• ((Pelvic splanchnic nerve::Parasympathetic to viscera; not the external anal sphincter.))
• ((Obturator nerve::Thigh adductors.))
• ((Ilioinguinal nerve::Sensory to groin and anterior scrotum/labia.))

After resection of a low rectal tumour, a patient develops erectile dysfunction. Which nerves were injured?

• ((Pelvic splanchnic nerves::☑️ Parasympathetic S2–4 — "point" — vulnerable during TME dissection.))
• ((Pudendal nerve::Somatic; injury causes sphincter weakness, not ED.))
• ((Hypogastric nerve::Sympathetic — injury causes retrograde ejaculation, not loss of erection.))
• ((Obturator nerve::Adductor weakness.))

👩‍⚕️ Point = Parasympathetic = erection. Shoot = Sympathetic = ejaculation.

A 68-year-old man with BPH is started on tamsulosin. Mechanism of action?

• ((5α-reductase inhibition::That's finasteride; works over months by shrinking the gland.))
• ((α1-adrenoceptor blockade::☑️ Relaxes prostatic and bladder neck smooth muscle, improving flow.))
• ((Antimuscarinic::Used for urge incontinence; would worsen retention in BPH.))
• ((PDE5 inhibition::Treats ED; tadalafil also helps LUTS but not tamsulosin's mechanism.))

A man develops confusion, nausea and hyponatraemia during TURP. Diagnosis?

• ((Septic shock::Would cause hypotension and pyrexia, not hyponatraemia from irrigation.))
• ((Acute haemorrhage::Causes hypovolaemia, not dilutional hyponatraemia.))
• ((TUR syndrome::☑️ Absorption of hypotonic irrigation fluid causes dilutional hyponatraemia and fluid overload.))
• ((Anaesthetic-induced hyponatraemia::Not a recognised intra-operative syndrome.))

👩‍⚕️ Modern bipolar TURP uses saline and has nearly eliminated TUR syndrome.

A 72-year-old man has back pain and PSA of 80. Bone scan shows multiple sclerotic lesions. Most appropriate hormone therapy?

• ((Tamsulosin::Treats BPH symptoms; no anti-cancer effect.))
• ((Finasteride::Lowers PSA but not used as primary treatment for metastatic prostate cancer.))
• ((Goserelin (LHRH analogue) with bicalutamide cover::☑️ Androgen deprivation; bicalutamide prevents tumour flare from initial testosterone surge.))
• ((Sildenafil::Treats ED.))

A 55-year-old woman leaks urine when she coughs. No urgency. Best first-line management?

• ((Oxybutynin::Antimuscarinic — for urge, not stress incontinence.))
• ((Mid-urethral sling::Surgical option after conservative measures fail.))
• ((Supervised pelvic floor exercises for at least 3 months::☑️ First-line for stress incontinence.))
• ((Indwelling catheter::Not appropriate for stress incontinence.))

A 70-year-old man on oxybutynin for "overactive bladder" develops a distended bladder and constant dribbling. Diagnosis?

• ((Stress incontinence::Leak on cough/exertion, not constant dribble with distended bladder.))
• ((Overflow incontinence::☑️ Anticholinergics worsened detrusor failure in undiagnosed BPH, causing chronic retention with overflow.))
• ((Urge incontinence::This is what was being treated; symptoms now differ.))
• ((Vesicovaginal fistula::Anatomically irrelevant in a man.))

👩‍⚕️ Always exclude bladder outflow obstruction before prescribing antimuscarinics in older men.

Which is the gold-standard investigation to classify the type of urinary incontinence?

• ((Urinalysis::Excludes infection; doesn't classify type.))
• ((Bladder diary::Useful screen but qualitative.))
• ((Cystoscopy::Visualises mucosa; doesn't measure function.))
• ((Urodynamics::☑️ Measures detrusor pressure and urethral function — distinguishes stress from urge.))

A 60-year-old diabetic smoker reports gradual-onset erectile dysfunction. Most likely cause?

• ((Psychogenic::Usually sudden, situational, with preserved morning erections.))
• ((Vasculogenic::☑️ Atherosclerosis of penile arteries; ED often heralds cardiovascular disease.))
• ((Neurogenic::Typically post-pelvic-surgery or spinal injury.))
• ((Endocrine::Less common; check testosterone and prolactin if suspected.))

A patient with chest pain takes GTN spray, then collapses with severe hypotension. Which drug must be excluded from his recent history?

• ((Tamsulosin::Causes postural hypotension but not the lethal interaction with nitrates.))
• ((Sildenafil::☑️ PDE5 inhibitors plus nitrates cause profound, sometimes fatal hypotension.))
• ((Finasteride::No significant interaction with nitrates.))
• ((Goserelin::No acute hypotensive interaction.))

A young man with sickle cell disease presents with a painful erection lasting 6 hours. Most appropriate immediate management?

• ((Observation and analgesia::Inadequate — ischaemic priapism causes irreversible fibrosis if untreated.))
• ((Sildenafil::Would worsen the situation.))
• ((Selective arterial embolisation::Treatment for high-flow (traumatic) priapism.))
• ((Corporal aspiration and intracavernosal phenylephrine::☑️ Standard emergency management of low-flow ischaemic priapism.))

👩‍⚕️ Painful + sickle cell = low-flow. Painless + perineal trauma = high-flow.

Revision summary

➡ Bladder body = endoderm (urogenital sinus); trigone = mesoderm (mesonephric ducts) — common site of TCC.

➡ Parasympathetic S2–4 (pelvic splanchnics): detrusor contracts → voiding.

➡ Sympathetic T11–L2 (hypogastric): internal sphincter contracts → storage.

➡ Somatic S2–4 (pudendal): external sphincter — voluntary continence.

➡ "S2–4 keeps the floor; T11–L2 holds the urine in you."

➡ Point = Parasympathetic = erection. Shoot = Sympathetic = ejaculation.

➡ BPH = transitional zone; prostate cancer = peripheral zone.

➡ BPH ladder: lifestyle → tamsulosin (α1) → finasteride (5α-reductase) → TURP.

➡ TUR syndrome = dilutional hyponatraemia from glycine irrigation.

➡ Prostate cancer: PSA + DRE → MRI → TRUS/transperineal biopsy → Gleason score. Sclerotic bone mets. Treat with LHRH analogues (goserelin) + bicalutamide cover.

➡ Stress = sphincter weak → pelvic floor exercises, duloxetine, sling.

➡ Urge = detrusor overactive → bladder training, antimuscarinics, mirabegron, Botox.

➡ Overflow = retention with leak (BPH, anticholinergics).

➡ Continuous = fistula or ectopic ureter.

➡ Urodynamics = gold standard for classification.

➡ ED: vasculogenic commonest; post-prostatectomy is neurogenic; sildenafil + nitrates = contraindicated.

➡ Priapism: low-flow (sickle, ischaemic, painful — emergency aspirate + phenylephrine) vs high-flow (traumatic, painless, embolise).