When a person is unable to pass urine, he or she is said to be in urinary retention. Urinary retention can be:
- Complete or incomplete (still able to pass urine but has a large amount of urine left in the bladder).
- Acute or chronic.
- Symptomatic or asymptomatic.
In men, an enlarged prostate can often obstruct the bladder, therefore urinary retention is more common in men than in women. The male-to-female ratio of urinary retention is 13:1, and the incidence is about 7 per 100,000 population per year.
Transient causes of urinary retention are:
- Immobility (e.g., post-operative).
- Urinary tract infection.
- Constipation or faecal impaction.
- Psychological problems.
- Endocrinological problems.
Long-term causes of urinary retention can be multifactorial and include:
- Idiopathic (unknown).
- Anatomic obstruction:
- In women, these include vaginal prolapse, tight sling, urethral stricture, urethral mass (e.g., diverticulum, caruncle), meatal stenosis (in postmenopausal women), and other vaginal mass (e.g., gynaecological tumour).
- In men, these include benign prostatic enlargement, urethral stricture, meatal stenosis.
- Large blood clots in the bladder can cause blockage (see haematuria).
- Bladder outlet dysfunction:
- Primary bladder neck obstruction.
- Dysfunctional voiding (e.g., Fowler’s syndrome in women, learned voiding dysfunction).
- Bladder dysfunction (bladder is unable to contract fully to expel all the urine or underactive bladder):
- Neurological disease (e.g., multiple sclerosis, spinal cord injury).
- Old age (incidence of underactive bladder is 30% by age 80).
- Medication-related (e.g., narcotics, anticholinergics).
- Pain or inflammatory disease.
- Pelvic surgery causing denervation of pelvic nerves.
- Psychogenic (e.g., conversion disorder).
- Failure of urinary sphincter relaxation (usually due to a neurological disorder). This is also called detrusor sphincter dyssynergia (DSD).
- Bladder outlet dysfunction:
Abdominal pain or bloating
Patients who are in complete urinary retention are unable to pass urine. They feel uncomfortable with a sensation of bloating in the lower abdominal area (where the distended bladder is).
Patients who are in partial urinary retention can still pass a bit of urine but describe struggling to start the stream, having to push and strain when voiding, prolonged voiding time, together with a slow urinary flow that can be intermittent. They often have a sensation of incomplete emptying and the need to pass urine again soon after having done one.
Some patients with partial urinary retention, describe needing to pass urine frequently, with strong urgency and/or waking up multiple times at night to void (see night-time symptoms).
- Some patients have infrequent voids, and have a long interval between each void. This can happen if the bladder sensation has also been affected, resulting in diminished awareness of bladder filling.
- Some describe a continuous unaware leaking called overflow incontinence.
- Partial urinary retention can also predispose the patient to getting recurrent bladder infections.
- Very rarely, urinary retention can also cause hold up of urine further upstream in the kidneys, resulting in kidney failure.
The basic tests that are helpful are:
Renal tract ultrasound
Renal tract ultrasound allows checking prostate volume in men, and post-void residual volume (PVR), which is the amount of urine that is left behind after a void. It can also screen for possible sequelae of urinary retention such as swelling of the kidneys or bladder stones.
Urine test is a collection of a midstream urine sample that can be tested for infection.
Blood test is a collection of a blood sample to check for kidney impairment.
Other tests that may be useful are:
Urodynamics is the definitive bladder function test to diagnose and find out the cause of urinary retention. It is a safe test that is done under local anaesthesia. It allows the clinician to assess if the bladder is obstructed vs. a bladder that does not generate a strong enough contraction. If there is an obstruction, the level of the obstruction and the cause can often be diagnosed during this test. The test is often combined with other techniques such as using X-ray (fluoroscopy), ultrasound, urethral pressure profile or EMG (a pressure sensor that assesses urethral sphincter activity).
Cystoscopy allows checking for urethral mass or stricture, prostate enlargement (in men), tight bladder neck, bladder stone, bladder wall changes (e.g., diverticulum or pouch, trabeculation or stretch marks, signs of infection).
Pelvic ultrasound in women
Pelvic ultrasound in women is an internal ultrasound (probe is placed in the vagina) that is useful to assess for urethral structures (such as a tight sling), gynaecological tumours, and lower abdominal masses arising from the female reproductive organs (e.g., ovarian cyst, uterine fibroid).
MRI pelvis in women
MRI pelvis in women allows assessment for urethral diverticulum (pouch in the urethra) or tumour (rare).
MRI brain and spine
MRI brain and spine allows assessment for neurological conditions causing retention (e.g., multiple sclerosis, lower spinal disc prolapse, nerve impingement, tumours).
Consequences of untreated urinary retention
If the cause of the retention is an obstruction, the patient will usually be very bothered with urinary symptoms like poor flow and needing to void again after having done one. The bladder may also develop secondary overactivity which causes symptoms like urinary frequency, urgency, urge leakage and waking up at night to pass urine (nocturia). If the obstruction does not get relieved after a long time, the bladder may undergo irreversible changes like forming diverticuli (pouches that don’t drain properly), and hypocontractility (bladder wall is so stretched that it is unable to generate a strong contraction during voiding). Very rarely, pressure in the bladder may ‘backflow’ into the ureters and kidneys, causing kidney damage.
As the urine does not clear properly (stasis), this predisposes the patient to suffer from recurrent bladder infections. Patients can get multi-resistant bacteria if they have been treated with multiple courses of antibiotics over the long term. Infections can rarely ascend from the bladder to the kidneys, making the patient very unwell (pyelonephritis).
The sediments at the base of the bladder can also form bladder stones which can worsen bladder infections and bladder symptoms. Surgery will be needed to remove the stones.
Chronic conscious or subconscious abdominal straining to assist with voiding, can result in the development of hernias, haemorrhoids or vaginal prolapses.
Medications are not effective and cannot restore bladder contractility. Antibiotics may be needed if there is an infection. Every individual is not the same; treatments are recommended according to the underlying cause of urinary retention.
Other treatment options are:
- Observation is suitable in certain patients who have mild chronic urinary retention, in the absence of bothersome symptoms or complications.
- Patients can be instructed to do timed voiding or double voiding.
- Pelvic floor physiotherapy and biofeedback.
- This is the mainstay of treatment if there is significant urinary retention. There are 2 forms of catheterisation: intermittent self-catheterisation (ISC) or indwelling catheterisation (IDC). Indwelling catheters can be inserted through the urethra (passage with drains the bladder to the outside) or through the lower abdomen (suprapubic catheter).
- ISC is always the preferred option over IDC, as long as the patient is able and willing to learn and perform the catheterisations. ISC is also useful in patients who have a urethral stricture (narrowing) as it allows intermittent dilatation of the passage.
Sacral neuromodulation is a bladder pacemaker, which may be suitable for some patients.
- Can potentially treat urinary retention due to functional obstruction (e.g., Fowler’s syndrome in women) or underactive bladder.
- Safe and minimally invasive.
- About 70% response rate seen in women with Fowler’s syndrome.
- Has 5% – 60% response rate for patients with the underactive bladder, resulting in more effective bladder emptying. Those with preserved bladder contractility have a higher response rate than those without.
- Lower response rate seen in neurogenic patients.
- An anti-spasm injection is administered into the bladder neck, external urethral sphincter, or pelvic floor to treat particular causes of functional obstruction.
- These are off label uses and are not commonly pursued.
Surgery is tailored to the particular cause of urinary retention.
- Men with a large prostate causing obstruction may be treated with transurethral resection of prostate or TURP.
- Women with an overly tight sling may have it divided or loosened. Sometimes surgery is done to free up a ‘stuck’ urethra (urethrolysis). If a large bladder vaginal prolapse is the cause of the obstruction, this can be repaired (cystocele repair).
- For both men and women, a tight bladder neck can be the cause of obstruction. This is more commonly seen in younger patients. A bladder neck incision can be done to relieve this. In men, this can result in retrograde ejaculation. If a stricture (narrowing) in the urethra is the cause of obstruction, a stricture repair or dilatation can be done. If a large bladder diverticulum (pouch) is sequestering urine and causing complications like infections, surgery to remove it may be considered (bladder diverticulectomy).