Urinary retention is the inability to voluntarily urinate. Acute urinary retention (AUR) is a medical emergency characterised by the abrupt development of the inability to pass urine over a period of hours (Joint Formulary Committee, 2021). AUR may occur due to urethral blockage, drug treatment (such as use of antimuscarinic drugs, sympathomimetics or tricyclic antidepressants), conditions that reduce detrusor contractions or interfere with relaxation of the urethra, and neurogenic causes. It may also occur postpartum or postoperatively.
Men are more likely to suffer AUR than women. There is a lack of recent studies. Past research indicates that 86% of hospital admissions for AUR involve men and 14% women. Older men are at greater risk of AUR and around 10% of men aged 70–75 will experience an episode of AUR (Cathcart et al, 2006). In the UK, more than 30 000 people are admitted annually with AUR and greater numbers attend emergency departments (Aning et al, 2007).
Why does AUR occur?
There are a number of reasons why AUR can occur. Causes can be grouped into four main categories (Selius and Subedi, 2008; Serlin et al, 2018):
- Outflow obstruction
- Infectious and inflammatory causes
- Neurological causes
- Iatrogenic causes/other causes.
Table 1 provides more details on the main causes of AUR.
Table 1. Mechanisms and causes of acute urinary retention
| Mechanism | Possible causes |
|---|---|
| Obstructive | Bladder calculi; bladder neoplasm; faecal impaction; gastrointestinal or retroperitoneal malignancy/mass; urethral strictures, foreign bodies, and stonesMale genitourinary: prostatic hypertrophy; meatal stenosis; paraphimosis; phimosis; prostate cancerFemale genitourinary: organ prolapse (cystocele, rectocele, uterine prolapse); pelvic mass, malignancy, uterine fibroid, ovarian cyst; retroverted impacted gravid uterus |
| Infectious and inflammatory | Aneurysmal dilation; bilharziasis (schistosomiasis); cystitis; echinococcosis; oedema; Guillain-Barré syndrome; herpes simplex virus; Lyme disease; periurethral abscess; transverse myelitis; tubercular cystitis; urethritis; varicella-zoster virusMale: balanitis; prostatic abscess; prostatitisFemale: acute vulvovaginitis; Behçet syndrome; vulval lichen planus; vulval lichen sclerosus; and vulval pemphigus |
| Neurological | Can be due to central nervous system problem causes such as cerebrovascular disease, spinal cord disease such as haematoma or spinal cord trauma, peripheral nerve damage and autonomic neuropathy |
| Iatrogenic/other | Trauma leading to disruption of posterior urethra and bladder neck, pharmacologic; postoperative complication; psychogenicMales: laceration; penile constricting bands; penile traumaFemales: postpartum complication; urethral sphincter dysfunction (Fowler syndrome) |
Source: adapted from Selius and Subedi, 2008; Serlin and Heidelbaugh, 2018
Investigations and treatment
A person with AUR is normally seen in the emergency department and has a full assessment to determine the cause of the AUR.
Assessment will include checking what medication the person has been taking as some can cause AUR. There is little research data; however, observational studies suggest that up to 10% of episodes of AUR may be caused by medication (Verhamme et al, 2005; 2008). Medication with anticholinergic activity such as antipsychotics, antidepressants and anticholinergic respiratory medication, opioids and anaesthetics, alpha-adrenoceptor agonists, benzodiazepines, non-steroidal anti-inflammatory drugs (NSAIDs), detrusor relaxants and calcium channel antagonists can lead to AUR (Verhamme et al, 2005; 2008).
Older men are at greater risk of developing drug-induced urinary retention, because they are likely to have prostatic hypertrophy and to take a number of medicines with anticholinergic effects (Verhamme et al, 2005; 2008).
History taking will enable the clinician to determine a possible diagnosis. The subjective, objective, assessment and plan (SOAP) method of documentation helps guide healthcare workers to use their clinical reasoning to assess, diagnose and treat a patient based on the information provided by them (Podder et al, 2020).
Physical examination in men will include a rectal and prostate examination (Aning et al, 2007). If a man has acute prostatitis the prostate will be tender and a penile discharge may be present. Phimosis and paraphimosis will be evident and if a man has a foreskin this will not normally be retractable.
If a man has prostatic hypertrophy the prostate will feel smooth and enlarged. In prostatic cancer, history and symptoms vary according to the stage of the disease. A man may have a history of weight loss and the prostate may have palpable nodules during a prostate examination (National Institute for Health and Care Excellence (NICE), 2019). Taking a patient history, checking for pyrexia, performing an examination and routine blood tests such as a full blood count and C-reactive protein enable the clinician to diagnose infection. Tests such as prostate specific antigen (PSA) will help detect prostate cancer.
If the individual is also constipated this will be treated. An enema is usually administered and if it enables the person to empty the bowel the person is then asked to try to pass urine. This can, if successful, avoid the need for catheterisation.
In women, AUR can develop because of gynaecological problems such as uterine prolapse, pelvic mass or malignancy and the woman may require a specialist referral.
A rare cause of urinary retention in adults taking sodium-glucose cotransporter-2 (SGLT2) inhibitors Fournier's gangrene (necrotising fasciitis of the genitalia or perineum). SGLT2 inhibitors are a class of drugs used to treat type 2 diabetes mellitus—examples are dapagliflozin, canagliflozin, empagliflozin, and ertugliflozin (Medicines and Healthcare products Regulatory Agency, 2019).
Blood tests are carried out in all patients with AUR to determine renal function and any haematological abnormalities. An ultrasound scan of the renal tract may be indicated if there is evidence of renal impairment (Aning et al, 2007).
Indwelling urinary catheterisation
In many cases an indwelling urinary catheter will be required to drain the bladder. A small minority of people develop postobstructive diuresis. This is excessive urine production following relief of bladder outlet obstruction. It is thought to be more common when bladder volume is one litre or more (Halbgewachs and Domes, 2015). Some NHS hospitals have a policy that anyone with AUR who has a bladder volume of 1 litre or more is catheterised in hospital and admitted for observation (NHS Borders, 2019).
Treatment
Most acute urinary retention occurs in older men and is caused by prostatic hypertrophy. Two types of medication are used to improve the likelihood of successful voiding when indwelling catheters are removed. These are alpha-adrenergic blockers and 5-alpha reductase inhibitors (Fisher et al, 2014; García-Perdomo et al, 2015; Gravas et al, 2021).
Alpha-adrenergic blockers are the first line of treatment, especially in men whose prostate is only moderately enlarged. Tamsulosin 400 micrograms once daily is commonly used. Alpha-adrenergic blockers relax the smooth muscle in the prostate and bladder neck and improve urinary flow. They increase the chances of a successful trial without catheter. They are fast acting and relieve obstruction within days or weeks. Side effects of alpha blockers include hypotension, tiredness, dizziness and headache. These drugs can increase the risk of falling as they cause blood pressure to drop and should be given at bed time to reduce this risk (Fisher et al, 2014; Fitzpatrick and Kirby, 2006).
5-alpha reductase inhibitors work by blocking male hormones and shrinking the enlarged prostate by up to 30%. As the prostate shrinks, flow rates improve. The usual drug is finasteride. This is less effective than alpha blockers but is useful if the prostate is particularly large, if flow rates are very low and if the patient is unable to tolerate an alpha blocker (Roehrborn, 2005). It is used if prostate problems cause haematuria. One 5 mg tablet is given daily. Side effects may include erectile dysfunction (occurring in 19% of cases), headache and dizziness. Male-pattern baldness, a result of high levels of male hormones, is often reversed and many men find their hair regrows. It usually takes around 3 months before the patient notices an improvement in urinary symptoms. If the drug is stopped, symptoms return (García-Perdomo et al, 2015).
Men with moderate-to-severe symptoms may benefit from a combination of alpha blockers and 5-alpha reductase inhibitors (Hollingsworth and Wei, 2010).
Trial without catheter
Catheterisation for AUR is usually performed in hospital and if the person is discharged with a catheter in place, a trial without catheter (TWOC) appointment is arranged. Traditionally, this has involved the person attending a hospital clinic as a day case. However, the Royal College of Nursing (RCN) has recommended that a TWOC is carried out in the person's home if possible, as it is a more relaxed environment and may reduce the infection risks associated with attending a hospital clinic (RCN, 2019). During the trial, the person's catheter is removed to see if urine can be passed without it.
The COVID-19 pandemic has affected clinic waiting times and, in some areas, community nurses are undertaking TWOCs in patient's homes (Nazarko, 2020).
Surgical options
Medical treatment is not always successful in prostatic hypertrophy and surgery may be required. Surgery should be carried out on an elective basis rather than as an emergency (Thomas et al, 2004; Yoon et al, 2015). Treatment options include standard surgery and newer techniques such as Rezum, a minimally invasive procedure that can be carried out as an outpatient. This involves injecting steam to destroy excess prostate tissue (Gravas et al, 2021; NICE, 2020).
Conclusion
AUR is a medical emergency and can cause a great deal of discomfort and anxiety in people who are affected. In most cases it can be easily treated, although urinary catheterisation may be required for a period of time. In some cases, the person may require surgical or other treatment. If treatment is unsuccessful and a urinary catheter is still required then the person should be taught to use intermittent self-catheterisation where possible.
KEY POINTS
- Acute urinary retention (AUR) is a medical emergency and around 30 000 people require hospital admission annually
- There are a number of reasons why an individual may develop AUR and a through history taking, physical examination and investigations are required to determine the cause of AUR
- The majority people who develop AUR are older males
CPD reflective questions
- Think about the characteristics of an adult most likely to develop acute urinary retention and how they are managed in your clinical area
- What action would you take if a patient you were caring for declined to take his morning dose of tamsulosin?
- If a trial without catheter is unsuccessful, what are the management options?