Reference values for the Nocturnal Bladder Capacity Index.

AIMS: The Nocturnal Bladder Capacity Index (NBCi) has been reported to be useful in distinguishing between nocturia caused by low bladder capacity and nocturnal polyuria. This paper aims to calculate reference values for NBCi from an asymptomatic population by comparing these with NBCi values from patients with lower urinary tract symptoms (LUTS) to obtain an indication of the sensitivity with which the NBCi detects low nocturnal bladder capacity. This paper also compares the sensitivity of rounded and unrounded calculations of NBCi. METHODS: Computer processed 3-day bladder diaries from 253 asymptomatic volunteers and 184 female patients with LUTS were analyzed. NBCi values were calculated from each diary using rounded and unrounded formulae. 90th and 95th centile NBCi cutoff values were obtained from frequency distributions. RESULTS: NBCi reference values from the asymptomatic group were 1.1 (unrounded) and 0.7 (rounded) for 90th centile, and 1.3 (unrounded) and 1.0 (rounded) for 95th centile. The use of the rounded formula gave identical NBCi values despite a large variation in V(n) /V(max) ratios whereas unrounded NBCis varied continuously with V(n) /V(max) ratios. The unrounded formula found significantly more elevated NBCis in the patient group. CONCLUSION: We suggest that an unrounded NBCi of 1.3 be considered a cutoff point above which reduced nocturnal bladder capacity should be investigated as a cause of nocturia. Rounding the NBCi lead to an underestimation of elevated values in a population of female patients with LUTS.

Normative bladder diary measurements in pregnant women.

OBJECTIVE: Studies have demonstrated a strong positive correlation between bladder capacity and total volume voided in asymptomatic non-pregnant women. Therefore, to adequately characterise the normative data, it was important to compare bladder capacity vs. 24-h volume (V24) relationships in our pregnant study population. Our objectives were to (1) collect normative bladder diary measurements from asymptomatic primigravid women, (2) investigate the relationship between these measurements and gestation of pregnancy, and (4) compare these normative measurements from pregnant women with those from asymptomatic non-pregnant women. We focused on measures of "bladder capacity" [average ("Vavg") and maximum volume per void ("Vmax")], ("V24"), and voiding frequency ("F24"). STUDY DESIGN: Three-day bladder diaries were collected from 41 primigravid women, one three-day diary per trimester. We compared our pregnant data with non-pregnant data previously collected by Amundsen et al. using identical methods. Relationship between variables analysed using the Kruskal-Wallace and Mann-Whitney tests. RESULTS: We found no significant differences across trimesters among bladder diary measurements (p-values: F24=0.711;Vmax=0.912;Vavg=0.894, and V24=0.675). A comparison between pregnant and non-pregnant data showed no significant difference between F24, but a significantly lower V24, Vavg and Vmax in pregnant women. Regression analysis showed no significant differences between the pregnant and non-pregnant, V24 vs. bladder capacity relationships. CONCLUSIONS: Pregnancy results in smaller bladder capacities and lower V24, with a normal relationship between V24 and bladder capacity, maintaining normal voiding frequency. We used our data to construct a nomogram to help clinicians compare the relative contributions of increased V24 and reduced bladder capacity to increased F24.

Bladder diary measurements in asymptomatic males: frequency, volume per void, and 24-hr volume.

AIMS: To collect bladder diary frequency and volume measurements from asymptomatic males and to use these data to develop clinical reference values. MATERIALS AND METHODS: Computer processed three-day bladder diaries were collected from 92 males (median age: 46.2 years; range: 20.6-84.6 years) defined as "asymptomatic" by questionnaire. Minimum (V(min)), maximum (V(max)), and average (V(avg)) volume per void (Vol/Void), 24-hr frequency (F(24)), and 24-hr volume (V(24)) were studied. Relationships of Vol/Void and F(24) to age and V(24) and of V(24) to age were investigated by regression analysis. RESULTS: V(max) and V(avg) increased as V(24) increased and decreased with increasing age (P < 0.0005). We found no significant relationship between V(min) and age, but V(min) increased with increasing V(24) (P < 0.0005). F(24) increased with increasing V(24) and increasing age (P < 0.0005). We found a concave downward, curvilinear relationship between age and V(24), which, while it did not reach statistical significance, was very similar in shape to age versus V(24) relationships found by other studies of larger datasets. CONCLUSIONS: Our results suggest that reference values of F(24) and Vol/Void should be adjusted for their relationships to the patient's age and V(24). Regression equations expressing these relationships can be used to make these adjustments. From frequency histograms of residuals the difference between the patient's actual and expected reference measurement can be ranked within the reference population as a percentile. We illustrate this method by using our results to calculate age- and V(24)-adjusted 5% "normal limit" tables of F(24), V(avg), and V(max).

Bladder diary measurements in asymptomatic females: functional bladder capacity, frequency, and 24-hr volume.

AIMS: To study the effects of age and 24-h volume (V(24)) on bladder diary measurements of voiding frequency (F(24)) and functional bladder capacity (FBC) from an asymptomatic female population. Also, to use these data to develop clinical reference values. (We use FBC as a generic term for bladder diary volume-per-void measurements.) MATERIALS AND METHODS: Computer-processed 3-day bladder diaries were collected from 161 females (median age: 46.6 years; range = 19.6-81.8 years) claiming no urological symptoms, previous pelvic surgery and diseases and medications effecting urologic function. Regression analysis was used to investigate relationships among age, FBC and V(24). RESULTS: Both FBC and F(24) increase as V(24) increases (P < 0.0005). With aging, F(24) increases (P = 0.026) and FBC may decrease slightly (P = 0.02-0.08). There is a concave downward, curvilinear relationship between age and V(24). We used multiple regression to generate tables of FBC and F(24) "normal limits" adjusted for these simultaneous influences of V(24) and age. Removing their relationships to age reduces the variability of FBC and F(24) reference values by 50% and 20%, respectively. CONCLUSIONS: Our finding, supported by others, that, with increasing V(24), FBC increases more than F(24) suggests an adaptive mechanism that adjusts FBC to urine production to minimize changes in voiding frequency. We illustrate adjustment of reference values for age and V(24) by calculating traditional clinical "normal limits." However, the probable large overlap between "normal" and "abnormal" suggests that it may be more useful to report bladder diary measurements as reference population percentiles rather than to designate them "normal" or "abnormal".

Bladder diary patterns in detrusor overactivity and urodynamic stress incontinence.

AIMS: Our aims were: (1) to describe and compare frequency-volume and incontinence episode patterns in patients with urodynamic stress incontinence (USI) and detrusor overactivity (DO) as measured by a hand-written and computer-analyzed bladder diary and (2) to compare degree of separation between these clinical groups produced by raw diary measurements and after age- and total-volume-adjustment against a reference population. MATERIALS AND METHODS: We studied 58 patients with USI, 29 with DO, and 22 with both USI and DO. From 3-day hand-written and computer-analyzed bladder diaries, we calculated average and maximum volume voided (Vol/Void), voiding frequency and volume voided over 24 hr, and number, size and type (whether accompanied by activity or urge) of incontinence episodes. RESULTS: Compared to the USI patients, the DO patients tended to have (1) higher voiding frequency, (2) lower Vol/Void, (3) more urge-related, than activity-related leaks, (4) smaller volume, and equally frequent leaks and (5) more severe incontinence symptoms. The age- and volume-adjusted percentiles better separated the USI and DO groups' frequency and volume measurements than did the raw measurements. Unexpectedly high percentages of our USI patients had low Vol/Void measurements, high voiding frequency, and predominantly urge-related leaks. A subgroup of 29 USI patients with "low" (average volume <30th reference population percentile) Vol/Void measurements had high incidences of urgency and urge-related leaks. CONCLUSIONS: Reference population percentiles better separate the frequency/volume patterns of USI and DO than do the raw measurements. We found a subgroup of USI patients that had an OAB-like clinical picture.

Normative bladder diary measurements: night versus day.

AIMS: To investigate bladder diary measurements from asymptomatic subjects in separate night and day periods, including their relationships to age and total volume voided. A major objective of this study was to generate age-adjusted reference values against which clinical measurements of nocturia can be compared. MATERIALS AND METHODS: Three-day bladder diaries were collected from 161 females and 92 males (age: median=46.5 years; range=19.6-84.6 years). We studied: average volume voided ("Vavg"), voiding frequency, and four urine production measures (volume, production rate, and their ratios to 24-hr values) RESULTS: Both day and night Vavg and frequency increase with increasing volume. The night increase is much steeper than the day increase. With aging, frequency increases, Vavg decreases, day production decreases and night production increases. These age effects are steeper for males than females. Adjusting for age by regression analysis reduces the night production measure's variability by about 40%, and expressing production rate as a percent of the 24-hr value reduces the variability by an additional 20%. CONCLUSIONS: We present regression equations that can be used to adjust night and day Vavg frequency and production rate reference values for the influences of age and total volume. Using these equations, we calculated a table of 95% confidence limits of night urine production and night frequency. The least variable night urine volume measurement studied was night/24-hr production rate; hence this may prove to be the most efficacious measurement to use in detecting nocturnal polyuria.

Bladder diary volume per void measurements in detrusor overactivity.

PURPOSE: We investigated the clinical usefulness of adjusting reference volume per void values for a recently reported strong tendency for volume per void to increase with increasing 24-hour volume in asymptomatic individuals. Our approach was to 1) test whether the adjustment increases the separation between volume per void measurements in patients with detrusor overactivity and an asymptomatic reference population, and 2) compare by regression analysis volume per void vs 24-hour volume relationships in patients with detrusor overactivity and asymptomatic volunteers. MATERIALS AND METHODS: We studied 3-day bladder diaries in 29 patients with detrusor overactivity and without genuine stress incontinence, an age matched control group of 29 asymptomatic women and a reference population of 161 asymptomatic women. Minimum, maximum and average volume per void measurements were calculated. The incidence of volume per void measurements below the 10th reference percentile was used as the measure of separation between the detrusor overactivity and asymptomatic populations. RESULTS: In patients with detrusor overactivity volume per void showed a highly significant positive relationship to 24-hour volume (p <0.0005). However, patient data points tended to lie below and parallel to control data points. Adjusting for the 24-hour volume relationship significantly increased the incidence of volume per void measurements below the 10th reference percentile in patients with detrusor overactivity (p <0.01). CONCLUSIONS: Adjusting for the 24-hour volume relationship increased the separation of patients with detrusor overactivity volume per void measurements from the reference population. Adjusting volume per void percentiles for the 24-hour volume relationship decreased the incidence of false-negative volume per void percentiles above the 10th percentile in patients with detrusor overactivity and false-positive volume per void percentiles below the 10th percentile in asymptomatic volunteers.