Nocturnal polyuria
Nocturnal polyuria is defined as an increase in urine production during the night but with a proportional decrease in daytime urine production that results in a normal 24-hour urine volume. With the 24-hour urine production within normal limits, nocturnal polyuria can be translated to having a nocturnal polyuria index (NPi) greater than 35% of the normal 24-hour urine volume. NPi is calculated simply by dividing NUV by the 24-hour urine volume. Similar to the inability of control urination, a disruption of arginine vasopressin (ADH) levels has been proposed for nocturia. Compared with the normal patients, nocturia patients have a nocturnal decrease in ADH level.Other causes of nocturnal polyuria include diseases such as

congestive heart failure
nephritic syndrome
liver failure
lifestyle patterns such as excessive nighttime drinking
sleep apnea increasing obstructive airway resistance. Obstructive sleep apnea sufferers have shown to have increases in renal sodium and water excretion that are mediated by elevated plasma atrial natriuretic hormone (ANH) levels. ANH is released by cardiac muscle cells in response to high blood volume. When activated, ANH releases water, subsequently increasing urine production. Bladder storage
Normal human bladder storage capacity varies from person to person and is considered 400 – 600 mL. A bladder storage disorder is any factor that increases the frequency of small volume voids. These factors are usually related to lower urinary tract symptoms that affect the capacity of the bladder. Some patients with nocturia have neither global nor nocturnal polyuria according to the above criteria.
The pilot study was conducted only on men. Diagnosis
Nocturia diagnosis requires knowing the patients nocturnal urine volume (NUV). The ICS defines NUV as “the total volume of urine passed between the time the individual goes to bed with the intention of sleeping and the time of waking with the intention of rising.” Thus, NUV excludes the last void before going to bed, but includes the first morning void if the urge to urinate woke the patient. The amount of sleep a patient gets, and the amount they intend to get, are also considered in a diagnosis.As with any patient, a detailed history of the problem is required to establish what is normal for that patient. The principal diagnostic tool for nocturia is the voiding bladder diary. Based on information recorded in the diary, a physician can classify the patient as having global polyuria, nocturnal polyuria, or bladder storage problems. A voiding bladder diary should record:
number of voids
timing of voids
volume voided
volume and time of fluid intakePatients should include the first morning void in the NUV. However, the first morning void is not included with the number of nightly voids. Causes
Polyuria
Polyuria is excessive or an abnormally large production or passage of urine. Increased production and passage of urine may also be termed diuresis. Polyuria is usually viewed as a symptom or sign of another disorder (not a disease by itself), but it can be classed as a disorder, at least when its underlying causes are not clear.