Acute Urinary Retention

See also:

• Chronic Urinary Retention
• Catheterising Bladders

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

• Pain
• Traumatic instrumentation
• Bladder overdistension
• Drugs (particularly opioids)
• Iatrogenic (e.g. suburethral sling procedures for stress incontinence³)
• Decreased mobility and increased bed rest

It is a reasonably common emergency with an incidence of primary AUR in the UK of approximately 3/1,000 men per annum.⁴ Increasing age is a significant risk factor for men: a man in his 70s has a 1 in 10 chance of experiencing AUR within 5 years; for those in their 80s, the risk is nearly 1 in 3.⁵ It is much less common and under-studied in women.

Usually the diagnosis is self-evident. The patient is very uncomfortable and unable to pass urine with a tender, distended bladder. However, it is necessary to consider the diagnosis in those unable to describe symptoms e.g. unconscious patients following trauma. History and examination should be directed towards determining a cause for the AUR. Whilst BPH is very common, rarer but serious causes such as cauda equina or cord compression must not be missed.⁶ See also Urological History Taking and Examination.

History

• Nature and duration of current symptoms e.g. anuria, pain.
• Any other associated symptoms e.g. fever, weight loss, sensory loss, weakness.
• Enquire regarding previous episodes of retention and history of lower urinary tract symptoms (LUTS)
• Consider precipitants e.g. alcohol consumption, recent surgery, UTI, constipation, large fluid intake, cold exposure or prolonged travel.
• Past medical history e.g. 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 (e.g. 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:

• AUR is usually painful whilst slowly obstructing pathological processes tend to be relatively pain free.
• Prostatic hypertrophy 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). For about 50% of those with AUR, the acute retention was their first symptom of underlying prostatic hyperplasia.⁷

• Urinalysis - check for infection, haematuria, proteinuria, glucosuria
• MSU
• Bloods:
  • FBC
  • U&E, creatinine, eGFR
  • Blood glucose
  • PSA (note, this is elevated in the setting of AUR so is of limited use at this stage)
• Imaging studies:
  • Ultrasound - commonly used as it can provide a measure of postvoid residual urine as well as looking for hydronephrosis and other structural abnormalities of the renal system.
  • CT - used to look for pelvic, abdominal or retroperitoneal mass causing extrinsic bladder neck compression.
  • MRI/CT brain - used to look for intracranial lesions (e.g. tumour, stroke, MS).
  • MRI 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 suspected cause of retention.

Initial management

• Immediate and complete bladder decompression usually with a Foley® urinary catheter. This can be undertaken in a community or hospital setting. The patient should then be referred to the urologists for longer term management.
• If this fails or is contra-indicated (e.g. urethral trauma or stenosis), refer to a urologist. Alternatives include angulated Coude® catheters or suprapubic catheters.
• The use of silver alloy indwelling catheters for catheterising hospitalised adults short-term (<14 days) reduces the risk of catheter acquired urinary tract infection, but the cost-effectiveness of their use remains unproven.⁸

As for any intimate examination, the patient should always have the option of a chaperone although many will decline.^9,10

Secondary management

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

• Until recently, 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.
• A more conservative approach involving the use of a trial without catheter (TWOC) has steadily become adopted as standard practice. This involves removing the catheter after 1-3 days: patients are able to void in 23-40% of cases and surgery, if needed, can be planned for a later date.¹¹ In the UK, this has resulted in a progressive decrease in the number of surgical procedures following a first episode of AUR, but a slight increase in the AUR recurrence rate.
• α1-blockers given before catheter removal increase the chances of a successful TWOC.¹²
• A high prostate-specific antigen level and postvoid residual urine volume, and limited response to alfuzosin treatment after a first AUR episode managed conservatively, may help to identify patients at risk of an unfavourable outcome.

• Urinary tract infections
• Renal failure
• Post-obstructive diuresis (marked natriuresis and diuresis with electrolyte disturbance including hypokalemia, hyponatremia, hypernatremia, and hypomagnesemia)

There is an increased mortality rate associated with AUR:¹³

• Overall, mortality at one year in men admitted to hospital for AUR was 2-3 times higher than for the general male population.
• The highest relative increase in mortality was in men aged 45-54 (standardised mortality ratio 10.0 for spontaneous and 23.6 for precipitated AUR) and the lowest for men aged 85 and over.
• The mortality rate associated with AUR increases strongly with age and comorbidity. There is a high prevalence of comorbidities such as cardiovascular disease, diabetes and chronic pulmonary disease in those with urinary retention.

Prevention of AUR in men with BPH may be achieved by long-term medical treatment (5-alpha reductase inhibitors alone¹⁴ or in combination with α-blockers¹⁵).
Some studies have developed algorithms for predicting when men with BPH are likely to develop AUR based on variables such as PSA levels, urinary peak flow rates and symptom scores.¹⁶ This may allow better targeted medical preventative treatment but this remains to be proven.