Variations of Nighttime and Daytime Bladder Capacity in Patients with Nocturia: Implication for Diagnosis and...

We subtyped patients with nocturia according to daily variations in urine production and bladder capacity.

Patients with 1 or more nocturia episodes per day were prospectively enrolled in this study. Post-void residual urine was collected and a 3-day frequency-volume chart was created. Nocturnal polyuria and bladder capacity were calculated for each patient. Reduced bladder capacity was defined as mean 24-hour bladder capacity less than 200 ml. Patients were categorized into 4 subgroups by the presence or absence of nocturnal polyuria and reduced bladder capacity.

Of the 84 patients enrolled in study 50 (59.5%) had nocturnal polyuria and 50 (59.5%) had decreased bladder capacity. Patients with reduced bladder capacity and nocturnal polyuria had significantly greater mean and maximum bladder capacity at night than during the day (p = 0.002) and the highest number of nocturia episodes (3, IQR 2-3). Patients with normal bladder capacity but with nocturnal polyuria had significantly larger mean and maximum bladder capacity at night (p = 0.033 and 0.016, respectively). In patients with reduced bladder capacity and no nocturnal polyuria we observed no significant variation in bladder capacity during the day vs the night. On multivariable analysis the body mass index (OR 1.28 per unit, 95% CI 1.04-1.58, p = 0.019) and severe nocturia (OR 6.26, 95% CI 1.71-22.92, p = 0.006) were risk factors for nocturnal polyuria while only severe nocturia was a predictive factor for reduced bladder capacity (OR 3.77, 95% CI 1.20-11.83, p = 0.023).

Patients with nocturnal polyuria have a different bladder capacity in the day and the night. Severe nocturia (3 or more episodes per night) predicts the presence of nocturnal polyuria and reduced bladder capacity. Our data suggest that in patients with severe nocturia those 2 conditions should be considered and managed.