Acute urinary retention

See also the separate Chronic urinary retention, Catheterising bladders and Benign prostatic h#perplasia articles.

What is acute urinary retention?

Acute urinary retention (AUR) is the sudden inability to pass urine. It is usually painful and requires emergency treatment with a urinary catheter.

Causes of urinary retention are numerous and can be classified by sex. Some of the commonest causes are listed here by category.

Anatomical causes

• In men - benign prostatic hyperplasia (BPH), meatal stenosis, paraphimosis, penile constricting bands, phimosis, prostate cancer.

• In women - prolapse (cystocele, rectocele, uterine), pelvic mass (gynaecological malignancy, uterine fibroid, ovarian cyst), retroverted gravid uterus.

• In both - bladder calculi, bladder cancer, faecal impaction, gastrointestinal or retroperitoneal malignancy, urethral strictures, foreign bodies, stones.

Infectious and inflammatory

• In men - balanitis, prostatitis and prostatic abscess.

• In women - acute vulvovaginitis, vaginal lichen planus and lichen sclerosis, vaginal pemphigus.

• In both - bilharzia, cystitis, herpes simplex virus (particularly primary infection), peri-urethral abscess, varicella-zoster virus.

Drug-related urinary retention

Up to 10% of acute urinary retention episodes are thought to be attributable to drugs. Those known to increase risk include:

• Anticholinergics (for example, antipsychotic drugs, antidepressant agents, anticholinergic respiratory agents).

• Opioids and anaesthetics.

• Alpha-adrenoceptor agonists.

• Benzodiazepines.

• Non-steroidal anti-inflammatory drugs.

• Detrusor relaxants.

• Calcium-channel blockers.

• Antihistamines.

• Alcohol.

Neurological

More often causing chronic retention but may cause acute urinary retention:

• Autonomic or peripheral nerve (for example, autonomic neuropathy, diabetes mellitus, Guillain-Barré syndrome, pernicious anaemia, poliomyelitis, radical pelvic surgery, spinal cord trauma, tabes dorsalis).

• Brain (for example, cardiovascular disease (CVD), multiple sclerosis (MS), neoplasm, normal pressure hydrocephalus, Parkinson's disease).

• Spinal cord (for example, invertebral disc disease, meningomyelocele, MS, spina bifida occulta, spinal cord haematoma or abscess, spinal cord trauma, spinal stenosis, spinovascular disease, transverse myelitis, tumours, cauda equina).

Other causes

• In men - penile trauma, fracture or laceration.

• In women - postpartum complications (increased risk with instrumental delivery, prolonged labour and caesarean section);³ urethral sphincter dysfunction (Fowler's syndrome).

• In both - pelvic trauma, iatrogenic, psychogenic.

BPH is by far the most common cause of urinary retention.

Acute urinary retention is often encountered postoperatively and the reasons for this are multifactorial:

• Pain.

• Traumatic instrumentation.

• Bladder overdistension.

• Drugs (particularly opioids).

• Iatrogenic - for example:

  • Urethral sling procedures for stress incontinence. ⁴

  • Posterior colporrhaphy.⁵

• Decreased mobility and increased bed rest.

Studies suggest that over five years, 10% of men over age 70 and close to one third in their 80s will develop acute urinary retention.¹ It is ten times more common in men than in women and highest in men aged over 70.⁶

Symptoms of acute urinary retention include:

• Being unable to pass urine.

• A strong urge to pass urine.

• A tender, distended bladder.

• General uncomfortableness.

It is necessary to consider the diagnosis in those unable to describe symptoms - for example, unconscious patients following trauma. History and examination should be directed towards determining a cause for the acute urinary retention. Whilst BPH is very common, rarer but serious causes such as cauda equina or cord compression must not be missed.

See also the separate Genitourinary history and examination (male) and Genitourinary history and examination (female) articles.

History

• Nature and duration of current symptoms - for example, anuria, pain.

• Any other associated symptoms - for example, fever, weight loss, sensory loss, weakness.

• Enquire regarding previous episodes of retention and history of lower urinary tract symptoms (LUTS).

• Consider precipitants - for example, alcohol consumption, recent surgery, urinary tract infection (UTI), constipation, large fluid intake, cold exposure or prolonged travel.

• Past medical history - for example, neurological conditions.

• Check medication (both prescribed and over-the-counter) for agents known to cause urinary retention.

Examination

• General - look for fever and signs of infection and systemic illness.

• Abdominal - a tender enlarged bladder with dullness to percussion well above the symphysis pubis, often almost to the level of the umbilicus.

• Genitourinary:

  • In men, look for phimosis or meatal stenosis, as well as urethral discharge and genital vesicles.

  • In women, look for evidence of:

    • Vulval or vaginal inflammation or infection.

    • Cystocele, rectocele or uterine prolapse.

    • Pelvic mass (for example, retroverted gravid uterus, uterine fibroid, gynaecological malignancy).

• Per rectum (PR) - check anal tone, prostatic size, nodules, tenderness, etc and exclude faecal impaction.

• Neurological - look for evidence of prolapsed disc or cord compression by checking lower limb power and reflexes as well as perineal sensation.

Distinguish from chronic urinary retention:

• Acute urinary retention is usually painful, whilst slowly obstructing pathological processes tend to be relatively pain-free.

• Prostatic hyperplasia may be associated with obstruction uropathy that is relatively painless but frequently comes to light when a superimposed acute obstruction occurs preventing effective urination ('acute-on-chronic' urinary retention).

• Urinalysis - check for infection, haematuria, proteinuria, glucosuria.

• MSU.

• Blood tests:

  • FBC.

  • U&E, creatinine, estimated glomerular filtration rate (eGFR).

  • Blood glucose.

  • Prostate-specific antigen will be elevated in men with urinary retention so is of little use at this stage in terms of detecting ongoing prostate disease.

• Imaging studies which may be done in secondary care:

  • Ultrasound - commonly used, as it can provide a measure of post-void residual urine as well as looking for hydronephrosis and other structural abnormalities of the renal system.

  • CT scan - used to look for pelvic, abdominal or retroperitoneal mass causing extrinsic bladder neck compression.

  • MRI/CT brain scan - used to look for intracranial lesions (eg, tumour, stroke, MS).

  • MRI scan of the spine - used to look for disc prolapse, cauda equina syndrome, spinal tumours, spinal cord compression, MS.

  • Investigations such as cystoscopy, retrograde cystourethrography or urodynamic studies may also be undertaken depending on the suspected cause of retention.

Initial management

• Immediate and complete bladder decompression. The National Institute for Health and Care Excellence (NICE) recommends that men with acute urinary retention should be immediately catheterised. An alpha-blocker should be offered before removal of the catheter.⁸

• Pharmacological treatment for postoperative retention (for example, cholinergics, intravesicle prostaglandin) was explored in a Cochrane review in 2010 as an alternative to catheterisation.⁹ It concluded that further studies were required but there has been no subsequent convincing evidence in the scientific literature that this approach is likely to be effective.

Secondary management

This is dependent on the cause of the acute urinary retention. For AUR caused by prostatic enlargement:

• Previously,this consisted almost exclusively of prostatic surgery within a few days (emergency surgery) or a few weeks (elective surgery) of a first AUR episode. It is known, however, that there is greater morbidity and mortality associated with emergency surgery and that morbidity increases with prolonged catheterisation.

• Trial without catheter (TWOC) has become a standard practice worldwide for men with BPH and AUR. In most cases, an alpha-blocker is prescribed before commencing TWOC and significantly increases the chance of success. Prolonged catheterisation is associated with an increased morbidity, but intermittent catheterisation is sometimes offered.

• UTIs.

• Acute kidney injury.

• Post-obstructive diuresis (marked natriuresis and diuresis with electrolyte disturbance, including hypokalaemia, hyponatraemia, hypernatraemia and hypomagnesaemia).

• Post-retention haematuria - up to 15% after rapid decompression via a catheter and usually self-limiting. ¹⁰

There is an increased mortality rate associated with acute urinary retention:¹¹

• The mortality rate associated with AUR increases strongly with age and comorbidity. There is a high prevalence of comorbidities, such as CVD, diabetes and chronic pulmonary disease, in those with urinary retention.

• In one study of 100,067 men with spontaneous AUR, the one-year mortality was 4.1% in men aged 45-54 years and 32.8% in those aged 85 years and over.

• In men aged 75-84 years with spontaneous AUR - the most prevalent age group - the one-year mortality was 12.5% in men without comorbidity and 28.8% in men with comorbidity.

• The use of less invasive methods to treat underlying causes (for example, prostatic stents) may help to improve the prognosis of men with comorbidities.

Postoperative urinary retention is usually transitory but can be prolonged in some cases. It is associated with longer hospital stays and, if undiagnosed or diagnosed late, can lead to prolonged bladder distension and permanent change to the bladder musculature. However most return to baseline voiding function with no need for long-term intervention (medication, catheterisation, or surgery). ¹²

Prevention of acute urinary retention in men with BPH may be achieved by long-term medical treatment (5-alpha reductase inhibitors alone or in combination with alpha-blockers).¹³