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Renal & Urinary System

Bladder Outlet Obstruction (BOO)

Blockage at the base of the bladder that reduces or prevents the flow of urine into the urethra. Can be acute (Acute Urinary Retention - AUR) or chronic.

Also known as: BOO, Urinary Obstruction

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Referral and warning signs

When to refer

Urgent referral to hospital (HC4/H/RR)/Urology for: Acute Urinary Retention requiring catheterization. Signs of AKI or hydronephrosis due to obstruction. Suspected malignancy causing obstruction. Failed Trial Without Catheter (TWOC). Need for definitive management of underlying cause (e.g., TURP for BPH, stricture repair).

Red flags

  • Inability to pass urine (AUR)
  • Palpable, painful bladder
  • Signs of AKI (rising creatinine, oliguria/anuria)
  • Fever/signs of infection with obstruction
  • Painless gross haematuria (suspect malignancy)
  • Neurological symptoms suggesting spinal cord issue

Signs and symptoms

  • Acute Urinary Retention (AUR): Sudden inability to pass urine despite full bladder, severe suprapubic pain, palpable distended bladder.
  • Chronic Bladder Outlet Obstruction:
  • - Obstructive LUTS: Weak stream, hesitancy, intermittency, straining, incomplete emptying, post-void dribbling.
  • - Storage LUTS: Frequency, urgency, nocturia, urge incontinence.
  • - Overflow Incontinence (in severe chronic retention): Involuntary leakage from an overly full bladder.
  • - Suprapubic discomfort or painless palpable bladder.
  • - Recurrent UTIs.
  • - Signs of Chronic Kidney Disease (if prolonged obstruction leads to hydronephrosis/renal damage).

Risk factors

  • Men: Benign Prostatic Hyperplasia (BPH), Prostate cancer, Urethral stricture, Meatal stenosis.
  • Women: Pelvic organ prolapse (cystocele), Urethral stricture, Pelvic masses (fibroids, ovarian tumours), Post-surgical scarring.
  • Both sexes: Bladder stones, Bladder tumours, Neurogenic bladder dysfunction (spinal cord injury, MS, diabetes), Medications (anticholinergics, opioids, decongestants), Faecal impaction.

Diagnosis

Clinical assessment

AUR diagnosed by inability to void and palpable/percussible bladder. Chronic BOO diagnosed by history of LUTS and evidence of obstruction (e.g., high PVR, findings on imaging/urodynamics). Identify underlying cause via history, DRE (prostate size/nodules), pelvic exam (prolapse), neurological exam.

Investigations

  • Bladder Scan or Catheterization: Confirm urinary retention, measure Post-Void Residual (PVR) volume (high PVR suggests BOO).
  • Urinalysis & Culture: Rule out/treat UTI.
  • Serum Creatinine/eGFR & Electrolytes: Assess renal function.
  • Kidney/Bladder Ultrasound: Assess PVR, bladder wall thickness, prostate size, hydronephrosis (kidney swelling due to back pressure), stones, tumours.
  • PSA (men): Assess prostate cancer risk.
  • Uroflowmetry: Measures urine flow rate.
  • Cystoscopy: Visualize urethra and bladder for strictures, stones, tumours.
  • Urodynamic Studies: Assess bladder pressure/flow relationships (specialist test).

Diagnostic criteria

Clinical presentation (AUR or chronic LUTS) + Objective evidence of obstruction (e.g., high PVR, imaging findings, urodynamics).

Management

Non-pharmacological management

  • Acute Urinary Retention (AUR): Immediate Bladder Decompression:
  • - Urethral Catheterization (Foley catheter - Size 16-18F usually). Use adequate lubrication, consider lignocaine gel. If difficulty, try coude tip catheter.
  • - Suprapubic Catheterization: If urethral catheterization fails or contraindicated. Performed surgically or percutaneously.
  • - Monitor post-obstructive diuresis after decompression (risk of dehydration/electrolyte imbalance).
  • Chronic BOO:
  • - Treat underlying cause (see specific conditions like BPH, Stricture).
  • - Timed voiding, double voiding techniques.
  • - Intermittent self-catheterization (for neurogenic bladder/atonic bladder).

Pharmacological treatment

  • Treat underlying cause:
  • - BPH: Alpha-blockers +/- 5-ARIs (see REN010).
  • - UTI: Antibiotics (see REN006).
  • Trial Without Catheter (TWOC) after AUR:
  • - Often attempted after starting alpha-blocker (e.g., Tamsulosin) for few days.
  • - Remove catheter and monitor ability to void and PVR.
  • Manage constipation (can worsen BOO).

Monitoring

Monitor urine output, PVR. Monitor renal function. Monitor LUTS severity. Monitor for complications.

Complications

  • Acute Kidney Injury (AKI) from post-renal obstruction
  • Chronic Kidney Disease (CKD) from chronic obstruction/hydronephrosis
  • Recurrent Urinary Tract Infections (UTIs)
  • Bladder stones
  • Bladder damage (detrusor hypertrophy/trabeculation, diverticula, hypotonic/atonic bladder)
  • Hydronephrosis / Hydroureter
  • Overflow incontinence

Prevention

  • Early management of BPH.
  • Prompt treatment of UTIs.
  • Avoid constipating medications if prone to retention.
  • Manage neurogenic bladder appropriately.

Patient education

  • Explain the cause of obstruction.
  • Catheter care instructions if applicable.
  • Signs of UTI or worsening obstruction.
  • Importance of treating underlying cause (e.g., BPH medications/surgery).
  • Fluid intake advice (avoid large volumes at once, esp. evening).
  • Voiding techniques.

Uganda-specific notes

BPH and urethral strictures are common causes. AUR is a frequent presentation. Catheterization (urethral or suprapubic) is key initial management. Access to specialist investigations (urodynamics, cystoscopy) and definitive surgery limited.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 7, Section 7.2.6

For learning and professional reference. Use current local guidance and clinical judgement.

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