The voiding diary is an essential tool for determining the cause of nocturia. We investigated whether there was a difference in the variables related to nocturia as expressed in fully recorded 24-hour voiding diaries and fully recorded 72-hour voiding diaries.

We analyzed 72-hour voiding diaries that were fully recorded by patients with lower urinary tract symptoms who visited our urology department from January through March 2018. All the fully recorded voiding diaries were analyzed twice by two methods. First, we selected and analyzed 24-hour voiding diaries from the 72-hour voiding diaries (which represented the patient’s usual voiding pattern)  by consulting with the patient and measuring the variables related to the nocturia. Next, we analyzed the 72-hour voiding diaries and measured the variables related to nocturia as the mean value. We investigated whether there were significant differences between the two methods in terms of total urine volume, nocturnal urine volume, the nocturnal polyuria index, the nocturia index, the actual number of nightly voids, the predicted number of nightly voids, and the nocturnal bladder-capacity index. The standard-format 3-day voiding diary released by the Korean Urological Association in 2016 was used, and the difference between the two methods was verified by means of a paired t test.

The fully recorded, standard-format 3-day voiding diaries of 50  patients (28 males and 22 females; mean age 61.8; range 18– 89 years) were analyzed. Total urine volume and nocturnal urine volume were significantly greater in the 24-hour voiding diary than in the 72-hour voiding diary (1688±674mL vs. 1559±543mL and 593±321mL vs. 537±266mL, respectively). There was no significant difference in the nocturnal polyuria index (0.35±0.14 vs. 0.34±0.12, respectively). The nocturia index and predicted number of night voids were significantly greater in the 24-hour voiding diary than in the 72-hour voiding diary (1.8±0.8 vs. 1.5±1.1 and 0.8±0.8 vs. 0.5±0.7, respectively). The maximum voided volume was significantly smaller in the 24-hour voiding diary than in the 72-hour voiding diary (325±125mL vs. 374±127mL, respectively). The nocturnal bladder-capacity index was also significantly smaller in the 24-hour voiding diary than in the 72-hour voiding diary (0.9±0.8 vs. 1.0±0.7, respectively).

The 24-hour voiding diary representing the patient’s usual voiding pattern showed no difference from the 72-hour voiding diary in the nocturnal polyuria index. The 24-hour diary recorded a smaller maximum voided volume than the 72-hour voiding diary, and so the nocturia index, predicted number of night voids, and nocturnal bladder capacity were calculated as small. The results of this study may be useful in analyzing partially incomplete voiding diaries.