Patients may experience bladder symptoms that only happen or are worse at night. These symptoms include waking up once or more overnight to urinate (nocturia) and incontinence.
Nocturia (waking up more than once to pass urine) is a very common complaint. It can result in insufficient rest and tiredness during the day. In the elderly, this is a common cause of falls as they make their way to the toilet with poor lighting or level of alertness.
There are many causes for this. A distinction must be made between those who wake up because of sleep disturbances (e.g., sleep apnoea) or psychological factors (stress, anxiety) and those who are woken up by a desire to pass urine. The former group goes to the toilet because they are awake and are not bothered by any bladder urgency.
Those who are woken by the bladder are classified into those with bladder problems and those with high urine output (polyuria).
- Individuals can wake up multiple times at night due to a bladder that either does not empty or does not store properly.
- A bladder that does not empty properly, does not take long to fill up again and provoke a desire to void. This is seen in patients with an underactive bladder or in men with obstruction from an enlarged prostate (see benign prostatic hyperplasia).
- A bladder that does not store urine properly can also cause patients to wake up with bladder urgency. Examples include those with an overactive bladder or a stiff bladder that does not stretch to hold more urine (poorly compliant bladder).
- Other conditions like bladder infections or bladder pain syndrome can sometimes cause bladder discomfort and wake people up.
Polyuria (high urine output)
- This can be divided into 24-hour polyuria (high urine output all day long) and nocturnal polyuria (high urine output only at night).
- The causes of 24-hour polyuria include high fluid intake, untreated type 1 and type 2 diabetes, diabetes insipidus and diabetes associated with pregnancy.
- Nocturnal polyuria is defined as night-time urine output of >20% of the daily total in young adults and >33% in older adults. The causes include heart failure with fluid retention, swelling of the legs, certain drugs like diuretics (fluid tablets) and drinking too much before bed.
Night-time incontinence can be due to a few causes:
- Bed-wetting that has not resolved since childhood (primary nocturnal enuresis)
- An overactive bladder
- An underactive bladder with overflow incontinence
Some leakages occur day and night and are continuous and constant. Some causes include:
- A severely incompetent sphincter (ring of muscle below the bladder that controls continence) called intrinsic sphincter deficiency (see female stress urinary incontinence and post-prostatectomy urinary incontinence).
- An abnormal connection between the urinary tract and the vagina – fistula.
- A congenital condition in which the ureter (the tube that drains the kidney) can come down and open in another site other than inside the bladder – ectopic ureter.
What are the investigations?
A urine analysis is first done to rule out a simple cause like an infection. A bladder diary recording the frequency and volume voided and the fluid intake is very useful to distinguish between the various causes of nocturia and incontinence.
A CT scan or an ultrasound can be done if anatomical abnormalities are suspected.
Urodynamics can be conducted to identify why a bladder would have storage problems. An overactive or underactive bladder and a poorly compliant bladder can be diagnosed with urodynamics.
If diabetes is suspected, the patient will be referred to an endocrinologist. A blood test called HBA1c can be done to give an indication of how well blood sugar level is controlled in that person with diabetes, over the last 3 months.
If heart failure is suspected, the patient will then be referred to a cardiologist for further investigations.
What are the treatments?
The treatment of these symptoms should be catered according to the cause identified. Simple measures like restricting evening fluid intake, changing the time of taking a fluid tablet and treatment of sleep apnoea can be useful.
Specific medical conditions
Diabetics lose sugar molecules in the urine. These sugar molecules attract water molecules and hence result in a larger volume of urine. In those with poorly controlled diabetes, they should seek specialist help to achieve better sugar control.
The fluid that accumulates in the legs all day in those with leg swelling, is redistributed in the body and excreted in the urine when that person lies down flat in bed at night. These patients may benefit from the use of compressive stockings during the day, leg elevation during the afternoon and a reduction in salt intake.
Bedwetting rarely persists into adolescence (1% by age 15) and treatments involve changes in fluid intake and behavioural therapy (a waking regimen with the aid of alarms and sensors). In young adults, urodynamics studies should be done to rule out bladder storage problems like an overactive bladder. Medications such as a bladder-calming drug (for overactive bladder) or ADH (anti-diuretic hormone) may be useful in some cases.
Medications can be helpful for some patients. In those with an overactive bladder, medications to calm the bladder can be effective. A medication called ADH can help to reduce night-time urine output and is used in select patients. There is a risk of electrolyte imbalance (low sodium) and exacerbating heart failure, so patients who are on it have to be monitored closely.
Surgery may be indicated if the underlying problem is prostatic obstruction in men. In patients with overactive bladder who do not respond to medications, anti-spasm bladder injection or sacral neuromodulation (bladder pacemaker) may be tried.
In patients with an underactive bladder that does not empty properly, sometimes they have to learn intermittent self catheterisation to manage it. In certain frail elderly patients, long-term indwelling catheterisation may be considered.
Read A/Prof Gani’s publication:
Download Urodynamic findings in patients with nocturia and their associations with patient characteristics - PDF (2900 Kb)