Urinary retention

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Urinary retention is the inability to empty the bladder completely or at all, leading to an accumulation of urine. It can be classified as:

  • Acute Urinary Retention (AUR): sudden, painful inability to void, often requiring emergency management.
  • Chronic Urinary Retention (CUR): gradual bladder dysfunction with residual urine >300mL, often painless.

Aetiology

1. Obstructive Causes:

  • Benign Prostatic Hyperplasia (BPH): most common cause in men over 50.
  • Urethral Stricture: narrowing of the urethra due to scarring.
  • Bladder Neck Obstruction: post surgical or congenital causes.
  • Urethral Calculi: kidney stones causing blockage.
  • Pelvic Masses: tumours or enlarged uterus (e.g., pregnancy, fibroids).

2. Neurological Causes:

  • Spinal Cord Injury: trauma affecting bladder control.
  • Multiple Sclerosis: disrupts nerve signals to the bladder.
  • Diabetic Neuropathy: affects bladder sensation and contraction.
  • Stroke: impairs voluntary control of urination.

3. Medication-Induced:

  • Anticholinergics: (e.g., oxybutynin, amitriptyline) reduce bladder contractility.
  • Opioids: cause urinary sphincter dysfunction.
  • Alpha-adrenergic agonists: (e.g., pseudoephedrine) tighten the bladder neck.
  • Calcium channel blockers: reduce detrusor muscle contractions.

4. Infectious and Inflammatory Causes:

  • Prostatitis: inflammation of the prostate.
  • Urinary tract infection (UTI): may cause bladder swelling and retention.

Pathophysiology

  • Urinary retention occurs when there is an imbalance between bladder filling and emptying.
  • Obstruction or impaired detrusor muscle contraction leads to urine accumulation.
  • Over time, chronic retention can cause bladder overstretching and dysfunction.
  • In severe cases, backpressure may lead to renal impairment (hydronephrosis).

Risk Factors

  • Male sex (due to BPH risk).
  • Older age.
  • History of urinary tract infections.
  • Recent pelvic or spinal surgery.
  • Neurological disorders (e.g., Parkinson’s disease, MS).
  • Long-term catheterisation.
  • Use of anticholinergic or opioid medications.

Signs and Symptoms

Acute Urinary Retention:

  • Sudden and severe lower abdominal pain.
  • Inability to pass urine despite a full bladder.
  • Suprapubic tenderness and distension.
  • Anxiety and restlessness.

Chronic Urinary Retention:

  • Incomplete bladder emptying.
  • Weak urine stream or hesitancy.
  • Nocturia (frequent urination at night).
  • Overflow incontinence (involuntary dribbling of urine).
  • Recurrent urinary tract infections.

Investigations

  • Bladder Ultrasound (Post-Void Residual Volume - PVR): measures retained urine (>300mL suggests chronic retention).
  • Urinalysis: checks for infection (UTI, haematuria).
  • Serum U&Es: assesses kidney function (hydronephrosis risk).
  • PSA (Prostate Specific Antigen): if BPH or prostate cancer suspected.
  • Renal Ultrasound: for suspected hydronephrosis.
  • Urodynamic Studies: assesses bladder function in neurological cases.
  • MRI/CT Spine: if spinal cord compression is suspected.

Management

1. Immediate Management of Acute Retention:

  • Catheterisation:
    • First line: urethral catheter insertion to relieve retention.
    • Suprapubic catheterisation: if urethral catheterisation fails.
  • Monitor Post-Catheterisation Diuresis: sudden decompression can lead to hypotension and post-obstructive diuresis.
  • Pain relief: paracetamol or NSAIDs.

2. Treat Underlying Cause:

  • BPH: alpha blockers (e.g., Tamsulosin 400mcg OD), 5-alpha reductase inhibitors (e.g., Finasteride 5mg OD).
  • UTI: antibiotics based on urine culture.
  • Neurological causes: referral to neurology or urology.
  • Medication review: stop or adjust drugs contributing to retention.

3. Chronic Urinary Retention Management:

  • Intermittent self Catheterisation: preferred in patients with neurogenic bladder.
  • Long-term Indwelling Catheter: consider only if intermittent catheterisation is unsuitable.
  • Bladder training: for improving detrusor muscle function.

4. Referral Criteria:

  • Recurrent urinary retention.
  • Hydronephrosis or renal impairment.
  • Suspected prostate cancer (raised PSA, abnormal DRE).
  • Neurological bladder dysfunction.
RenalmypanotesUrinary retention