Bladder Outflow Obstruction

Definition/diagnostic criteria BOO is a condition characterised by a blockage at the base or neck of the bladder, impeding urine flow. Diagnosis is often based on a combination of symptoms, urodynamic studies and imaging.

Epidemiology The prevalence of BOO is significantly higher in older men, primarily due to benign prostatic hyperplasia (BPH). In the UK, about one-third of men over 50 show symptoms of BOO. Although less common, women can also be affected, often due to pelvic organ prolapse or bladder neck obstruction.

Clinical features: BOO typically presents with lower urinary tract symptoms (LUTS), including hesitancy, poor stream, frequency, urgency and nocturia. In severe cases, it can lead to urinary retention, infection or renal impairment. The severity of symptoms can be assessed using the International Prostate Symptom Score (IPSS).

Initial assessment involves a physical examination, focusing on the abdominal and genital areas. A digital rectal examination (DRE) is essential in men to evaluate prostate size and texture.


  • Urinalysis is performed to rule out infection or haematuria. Serum creatinine measurements help assess renal function.
  • Uroflowmetry and post-void residual (PVR) volume measurement are key investigations. A PVR >50ml suggests significant retention. Urodynamic studies can confirm the diagnosis and assess the severity of obstruction.
  • Imaging – typically ultrasound – may be used to evaluate the anatomy of the bladder, prostate and kidneys.

Treatment Treatment depends on the severity of symptoms and the underlying cause.

  • For mild cases, watchful waiting with lifestyle modifications is often advised. Medications include alpha-blockers (e.g., tamsulosin) and 5-alpha-reductase inhibitors (e.g., finasteride) for men with prostatic enlargement.
  • For moderate to severe symptoms, minimally invasive therapies like transurethral resection of the prostate (TURP) may be indicated. In cases where medication or less invasive procedures are not effective, open surgery may be necessary.
  • Catheterisation is used for acute urinary retention. Long-term management may involve intermittent self-catheterisation or, in certain cases, long-term catheterisation.

Prognosis The prognosis of BOO varies depending on the underlying cause, the severity of obstruction and the timeliness of treatment. Early intervention can alleviate symptoms and prevent complications such as bladder damage or renal failure. Chronic BOO, especially if untreated, can lead to significant morbidity.

For men with BPH, surgical intervention often provides significant symptomatic relief. In women, addressing the underlying cause, such as prolapse, often improves symptoms.

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