Nocturnal Polyuria (NP) is a common finding in males with nocturia and/or lower urinary tract symptoms (LUTS) [1]. Nocturnal polyuria and nocturia have detrimental effects on quality of life and overall health of men, mainly due to sleep disturbances. This condition needs a multidisciplinary management and should be assessed to avoid misleading diagnoses and following useless and/or unsatisfactory treatment. Aims of the study were to evaluate in males with LUTS: 1) the prevalence of nocturnal polyuria; 2) the relation between nocturnal polyuria, nocturia, and both uroflowmetry (UF) and International Prostate Symptom Score (IPSS).

From September 2016 to Novembre 2017 we enrolled 461 consecutive patients with lower urinary tract symptoms into a prospective double-centre study. Data collected were: detailed medical history, UF, post void residual urine volume (PVR), a self-administered IPSS and a 3 days frequency volume charts (FVC), indicating “bedtime” and “waking time”. For each patient, we calculated the Nocturnal Polyuria index (NPi)  which is the most widely used index of NP, indicating the ratio of nocturnal urine production (NUP) to 24-hour urine production expressed as a percentage.
Frequency, voided volume and Nocturnal Polyuria index (NPi) were assessed by 3 days-FVC, and compared with IPSS data. Nocturnal polyuria was defined as a NPi >33%, and severe nocturnal polyuria as NPi >50% [2], nocturia as at least 1 mean episode of nocturnal voiding at 3 days-FVC. Analyses were performed considering: total IPSS score; IPSS-item #2 (frequency score); IPSS-item #7 (nocturia score); IPSS-item #8 (bother score); peak flow (Qmax) at the UF; PVR. A subanalysis according to patients age was also performed. For statistics Kruskal-Wallis test was used.

Both IPSS and 3-days FVC were completed in 162 patients (mean age 70.95 ± 8.04 yrs). Prevalence of noctunal polyuria was 54,9% (89/162 pts), while severe nocturnal polyuria rate was 9.88% (16/162 pts) with a mean NPi of 34.4% ±11,2. Table 1 shows nocturnal polyuria prevalence according to patients ages. 
Frequency volume chart analysis showed nocturia in 110 pts (68%), of these 69% (76/110) referred nocturnal polyuria. Nocturia was documented in 85% of the population with nocturnal polyuria (76/89). Similar results can be found in literature [3]. In Table 1 are also listed median IPSS scores, Qmax, and PVR stratified according to NPi. Only median IPSS #7 and total IPSS showed significant difference.

Our data showed a high nocturnal polyuria prevalence (> 50%) among males complaining lower urinary tract symptoms. In only a minor part of the patients nocturnal polyuria was severe (<10%). Nocturnal polyuria was diagnosed also in patients without nocturia. More than 2/3 patients reporting nocturia had nocturnal polyuria. Therefore, misleading this two pathological conditions could involve useless and/or unsatisfactory treatments. These data stress the necessity to a whole evaluation of males with nocturia and not a simple focus on nocturia per se.
Nocturnal polyuria influenced outcomes of median IPSS domain 7 and total IPSS score but not findings of IPSS domain related to quality of life and frequency. UF data (Qmax and PVR) did not change according to NPi. Therefore, nocturnal polyuria did not impact the micturition and the bladder emptying.

Nocturnal polyuria was a common condition in males with lower urinary tract symptoms and nocturia, however it was severe only in a minority. Nocturnal production of urine did not influence the voiding pattern, nor the bladder emptying. IPSS was a valid tool to diagnose nocturia, while only frequency volume charts could identify nocturnal polyuria. Therefore, the use of frequency volume charts is crucial to obtain a correct diagnosis in men reporting nocturia. Our data suggest that physicians should look for nocturnal polyuria among males with lower urinary tract symptoms and nocturia in order to manage these patients with the most appropriate treatments using both frequency volume charts and and IPSS questionnaire.

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van Doorn, B., Blanker, M. H., Kok, E. T.et al.. Prevalence, incidence, and resolution of nocturnal polyuria in a longitudinal community-based study in older men: the Krimpen study. European urology, 2013.
Matthiesen, T. B., Rittig, S., Mortensen, J. T., & Djurhuus, J. C., Nocturia and polyuria in men referred with lower urinary tract symptoms, assessed using a 7-day frequency-volume chart. BJU international, 1999.