Nocturia is defined as the need to awaken from sleep one or more times to urinate. This affects men and women equally, increases in prevalence as we get older, and can be sleep-disruptive. Although only 3% of adults under 30 years old will awaken from sleep two or more times in order to urinate, this increases to 40% after age 70. Nocturia can have a negative impact on quality of life, resulting in daytime fatigue, an increased risk of traffic accidents, and an increased incidence of risk of fall-related nighttime injuries.
Nocturia has many different causes, sometimes related to sleep disorders, sometimes to fluid or medication issues, sometimes to medical problems and sometimes on the basis of urological problems.
Sleep disorders include insomnia, obstructive and central sleep apnea, restless legs syndrome, and parasomnias. Under these circumstances, nocturia occurs because of poor quality sleeping, not because the patient is awakened as a result of a full bladder. Excessive fluid consumption before bedtime, especially caffeinated beverages (coffee, tea, colas, chocolate) and alcohol, will often cause nocturia. Patients on diuretic medications will have a tendency towards frequent nocturnal visits to the bathroom.
Polyuria is defined as a urine output in excess of 2500 ml/24 hours. It occurs in response to conditions that cause increased fluid intake, which in turn leads to excessive urine production. Polyuria causes both daytime as well as nighttime urinary frequency. Common causes of polyuria are diabetes mellitus and diabetes insipidus.
Nocturnal polyuria is defined as an increase in nocturnal urine production with a corresponding decrease in daytime urine production. Also known as physiologic nocturnal dieresis, it may result from a disruption in the nighttime secretion of the hormone responsible for retaining fluid, known as anti-diuretic hormone. Fluid accumulation in the lower extremities that gets reabsorbed into the circulation is another cause for nocturnal polyuria. This fluid accumulation, known as edema, can be on the basis of congestive heart failure, venous stasis, hypoalbuminemia, or excessive salt intake. This fluid tends to accumulate in the legs with gravity. Upon assuming the recumbent position when sleeping, this fluid returns to the circulation causing the kidneys to increase urine production.
Nocturia can also be on the basis of bladder storage problems, including failure to completely empty the bladder, prostate enlargement, urethral obstruction, overactive bladder, small capacity bladder, a bladder that is not stretchy and compliant, and bladder irritation from cancer, stones, interstitial cystitis, infections, etc. Neurologic conditions, including stroke, Parkinson’s disease, multiple sclerosis, spinal cord injury, etc., can often engender frequent voiding. Extrinsic pressure on the bladder, such as occurs with pregnancy, can give rise to nocturia. It can also occur when a uterine fibroid or rectal fullness due to gas or constipation, puts pressure on the urinary bladder.
Evaluation of nocturia starts with a medical history, particularly with respect to diabetes, hypertension, congestive heart failure, edema, neurologic diseases, sleep disorders, and urological surgery. Medication review is important, especially with regard to diuretics. Fluid intake patterns need to be examined carefully. Physical examination includes digital rectal exam in men and a pelvic exam in women. Urine analysis is obtained and the volume of urine remaining after completing voiding is ascertained. The principal diagnostic tool for assessing nocturia is the 24 hour bladder diary in which the patient keeps a record over a 24 hour period of the timing of voids, the number of voids, and volume of urine voided. Based upon this diary, the nocturia can be classified as polyuria, nocturnal polyuria, or bladder storage problems.
If fluid intake is found to be excessive, simple moderation of fluid intake will be helpful, particularly with respect to caffeinated beverages and high-fluid content foods. Restricting fluid intake after dinner is often advisable. Minimizing high salt content foods and table salt can help prevent fluid retention. If edema is the issue, compression stockings worn during the day as well as elevating the legs can be of value. Diuretics taken during the late afternoon may decrease fluid accumulation.
Medications may be helpful depending upon the cause of the nocturia. DDAVP, a synthetic hormone often used for childhood bedwetting, has proven very useful for adults with nocturnal polyuria. Taken right before bedtime, this medication decreases the production of urine by the kidneys. Anti-cholinergic medications including Tolteridine, Oxybutinin, Trospium, Solifenacin and Darifenacin can be useful agents when an overactive bladder gives rise to the nocturia. Alpha-blocking medications including Tamsulosin and Alfuzosin and 5-DHT inhibitors including Finasteride and Dutasteride can be helpful when prostate obstruction engenders the nocturia.
Andrew L. Siegel, M.D.
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