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Urinary Retention

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Overview

Urinary retention describes the inability to pass urine and empty the bladder. Its causes can include blockage or narrowing of the urethra, neurological dysfunction, bladder dysfunction, and certain drugs.

Acute urinary retention is a medical emergency characterised by the sudden inability to pass urine (usually over hours). 

Chronic urinary retention is more gradual and occurs over months-years.

High pressure urinary retention describes the presence of hydronephrosis and deranged renal function tests.

Low pressure urinary retention is where no hydronephrosis is present and renal function tests are normal.

Epidemiology

  • Acute urinary retention is around 10 times more common in men than in women
    • Estimates show around 1 in 3 men >80 years old will develop acute urinary retention over 5 years
  • Chronic urinary retention is more common in men due to cause of lower urinary tract symptoms such as benign prostatic hyperplasia, but there is still a significant incidence in women

Causes

Causes of urinary retention include:

  • Urologic causes:
    • Renal causes:
    • Prostate causes:
      • Benign prostatic hyperplasia – the most common cause
      • Other causes include: prostatitis and prostate caner
    • Urethral causes:
    • Bladder causes:
    • Penile causes:
  • Drug-induced causes – thought to affect up to 10% of cases of acute urinary retention:
    • Drugs with anticholinergic effects are a notable cause, such as:
      • Tricyclic antidepressants – such as amitriptyline, clomipramine
      • Antipsychotics – such as quetiapine, clozapine
      • Antimuscarinics – such as ipratropium, tiotropium, oxybutynin, atropine, and some first-generation antihistamines such as promethazine
    • Other drugs include opioids, NSAIDs, and alpha agonists 
  • Neurologic causes – tend to be chronic, but can be acute:
  • Infectious causes:
  • Other causes:
    • Constipation
    • Pregnancy complications (e.g. prolonged labour, injuries during caesarean section)
    • Decreased mobility
    • Iatrogenic (e.g. genitourinary surgery) and post-operatively
    • Psychogenic
    • Pelvic trauma

Presentation

Acute urinary retention

Acute urinary retention usually develops over hours with an inability to pass urine. Features include:

  • Lower abdominal pain – this is often severe, and patients may be restless
  • A tender, enlarged bladder may be felt with dullness to percussion
  • Delirium or an acute worsening of dementia may be present in older patients
  • Features of an underlying cause (e.g. phimosis or enlarged prostate)

Physical examinations including a digital rectal exam, neurological exam, and pelvic exam (for women) may narrow down the suspected underlying cause.

Chronic urinary retention

Chronic urinary retention is more insidious and develops over months to years. It tends to be painless. Other features include:

Investigations

Acute urinary retention

Initial investigations include:

  • Urinalysis and culture:
    • May identify infection
    • May only be possible after catheterisation
  • Urea and electrolytes (U&Es):
    • May identify kidney injury
  • Full blood count (FBC):
    • May show leukocytosis suggesting infection
  • C-reactive protein (CRP):
    • Non-specific marker of inflammation, may be elevated in infection
  • Ultrasound scan:
    • Commonly used and can screen for hydronephrosis, genitourinary tract abnormalities, and measure post-void residual urine volume

Further tests depend on the suspected underlying cause. Prostate-specific antigen (PSA) is not usually measured in acute urinary retention as it is often elevated.

Chronic urinary retention

Initial investigations include:

  • Urinalysis and culture:
    • May identify infection
    • May only be possible after catheterisation
  • Urea and electrolytes (U&Es):
    • May identify kidney injury
  • Blood glucose:
    • May identify diabetes mellitus
  • Full blood count (FBC):
  • C-reactive protein (CRP):
    • Non-specific marker of inflammation, may be elevated in infection
  • PSA testing:
    • Considered if LUTS suggest benign prostatic hyperplasia, the prostate gland feels abnormal on examination, or if the person is concerned about cancer
  • Ultrasound scan:
    • Commonly used and can screen for hydronephrosis, genitourinary tract abnormalities, and measure post-void residual urine volume.

Further tests depend on the suspected underlying cause. Some other tests include:

  • MRI/CT of the urinary tract
  • Urodynamic studies
  • IV pyelography
  • Renal radionuclide scanning

Management

Acute urinary retention

  • 1st-line: immediate catheterisation and manage underlying cause
    • This relieves urinary retention and pain
    • Before the catheter is removed, a 2-day course of an alpha-blocker should be given to manage acute urinary retention
  • Refer patient to the corresponding speciality (e.g. neurologists, gynaecologists, or urologists). If no cause is found, refer to urology.

Chronic urinary retention

  • 1st-line: investigate and manage underlying cause
  • Self- or carer-administered intermittent urethral catheterisation is tried first before considering indwelling catheterisation

Complications

  • Post-obstructive diuresis:
    • A temporary increase in urine output by the kidneys after decompression as the kidneys adjust back to normal.
    • This can become excessive and result in dehydration and electrolyte imbalances, therefore, some patients require IV fluids and correction of electrolytes
  • Hydronephrosis and renal injury:
    • Increasing pressure in the kidneys can lead to swelling which can reduce renal blood flow. This can lead to potentially irreversible renal damage and chronic kidney disease if not treated early.
  • Infection and septic shock:
    • Urinary flow obstruction may have an associated infection or may become infected, increasing the risk of sepsis and septic shock.
  • Post-retention haematuria:
    • Occurs due to rapid decompression and usually self-limiting

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