Home Forums Other Specialities Nephrology/Urology ACUTE URINARY RETENTION- BACK TO BASICS.

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    Differential diagnosis -ACUTE URINARY RETENTION.
    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.

    Urinalysis – check for infection, haematuria, proteinuria, glucosuria.
    Blood tests:
    U&E, creatinine, eGFR.
    Blood glucose.
    Prostate-specific antigen (PSA). NB: 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 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, 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 (eg, urethral trauma or stenosis), refer to a urologist. Alternatives include angulated Coude® catheters or suprapubic catheters.

    A Cochrane review suggested that the use of silver alloy indwelling catheters for catheterising hospitalised adults short-term (<14 days) reduced the risk of catheter-acquired UTI but subsequent studies have found that they are not cost-effective.

    Pharmacological treatment for postoperative retention (eg, cholinergics, intravesicle prostaglandin) has been explored as an alternative to catheterisation but further studies are required.
    As for any intimate examination, the patient should always have the option of a chaperone, although many will decline.

    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.

    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. Such an approach requires impeccable communication between the hospital services and primary care.

    Alpha-1 blockers given before catheter removal increase the chances of a successful TWOC.

    A high PSA level and post-void 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.

    Renal failure.
    Post-obstructive diuresis (marked natriuresis and diuresis with electrolyte disturbance, including hypokalaemia, hyponatraemia, hypernatraemia, and hypomagnesaemia).
    Post-retention haematuria - 2-16% in one study after rapid decompression via a catheter and usually self-limiting.

    There is an increased mortality rate associated with AUR:

    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 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.

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

    Prevention of AUR in men with BPH may be achieved by long-term medical treatment (5-alpha reductase inhibitors alone or in combination with alpha-blockers).[
    One study suggested that delaying 5-alpha reductase inhibitor therapy resulted in an increased risk of developing AUR.
    Some studies have developed algorithms for predicting when men with BPH are likely to develop AUR, based on variables such as selective alpha-1 blockers, prostate volume, PSA level, and maximal flow rate.

    G Mohan.

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