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Utilising frequency volume charts

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VOL: 99, ISSUE: 01, PAGE NO: 52

Anthony Hinchliffe, FRCS, consultant urologist, Weston Area Health NHS Trust, Weston-super-Mare

Sharon Tonkin, RGN, Lyn Kirkwood, RGN, clinic nurse specialists, Weston Area Health NHS Trust, Weston-super-Mare

Anthony Hinchliffe, FRCS, consultant urologist, Weston Area Health NHS Trust, Weston-super-Mare

Frequency and nocturia are common lower urinary tract symptoms associated with a variety of organic pathologies as well as with life style and psychological factors.

A frequency volume chart is a patient’s recorded account of times and volumes of urine voided over several days and nights. The purpose is to obtain an objective record of one aspect of lower urinary tract symptoms to augment the history and other patient-recorded information, such as the international prostate symptom score (IPSS).

Fluid intake is more difficult to measure accurately. The patient and the continence adviser can clarify details of type and quantity of fluid intake as well as other factors as they study the frequency volume chart together.

The frequency volume chart alone can give immediate insight into several problems underlying lower urinary tract symptoms, but is always used in combination with measures of urinary voiding flow rates and ultrasound-estimated post-void residual bladder volume, sometimes progressing to functional urodynamic measures if necessary.

Design of frequency volume charts Frequency volume charts have been developed in different ways over the past 30 years so that there is no standard validated format. The design should accommodate ease of use for the patient and adviser.

The charts illustrated have a seven-day grid with 24 boxes on each of the seven lines to record separately each voided urinary volume during any one hour. The exact times are not requested, and there is room to record several voids in each box if necessary. A line across a box records bedtime and rising for the day, and incontinent episodes are noted with a ‘W’.

Current medication is listed at the bottom of the chart. Recording over one week takes into account the effect of variations in peoples’ daily life and activities through the week and weekend.

Fig 1 is a frequency volume chart completed by a young man. This shows an unremarkable pattern of urinary production and voiding, with his largest void on rising in the morning - that is, his usual maximal functional bladder capacity.

Fig 2a and 2b These charts are from a 75-year-old man with normal flow rates and no post-void residual urine.

Fig 2a shows that his 24-hour urine output is large, and over one third of this is produced during the night hours, although he is not drinking at this time - an example of nocturnal polyuria. His maximal functional capacity is during the night hours, and during the day he is voiding much smaller individual volumes, probably indicating detrusor instability.

On one occasion he had an incontinent episode before voiding only 200ml of urine. On questioning, he revealed that he was drinking up to 3.5 litres of tea during the day, which may also have contributed to the detrusor instability.

His second chart (Fig 2b), completed after he had modified his fluid intake, shows that his problem of frequency has largely resolved, although he still voided small volumes in the day, which improved after a period of bladder training.

Fig 3 is the chart of a 74-year-old man who complained of a weak voiding stream, urgency and nocturia. His flow rate showed evidence consistent with mild bladder outlet obstruction, and his frequency volume chart showed a marked nocturnal polyuria, although his last drink was taken at 8pm in the evening. He was prescribed an alpha blocker, alfusozin, which works by relaxing the muscles of the bladder neck and prostatic urethra, resulting in a normal (25ml per second) maximal urinary flow rate.

However, a second chart showed that nocturia persisted, confirming that this was not secondary to bladder outlet obstruction. In the days before objective measurements were routinely used and pharmacotherapy was not available he might have been advised to undergo prostatectomy and would have had a disappointing result.

Nocturnal polyuria is common in elderly people, causing troublesome nocturia. Although the main hormonal mechanisms controlling sodium and water excretion and consequently affecting urinary volume are well known, not all factors - including the more recently studied naturetic peptides influencing circadian rhythm of urine secretion - are fully understood. Therapeutic attempts to restore normality in urinary voiding have met with variable results (Reynard et al, 1998).

Interpretation The above are a few examples of how frequency volume charts can help to uncover problems of fluid balance. Abrams and Klevmark (1996) recognised six patterns, ranging from the normal to nocturnal polyuria.

Although high fluid intake may be the result of choice or habit, it may indicate significant underlying causes, such as diabetes mellitus or insipidus. Reduced fixed volumes during the day and night may indicate a small fixed bladder capacity due to a serious underlying condition, such as interstitial cystitis or bladder carcinoma in situ.

Reduced variable volumes during the day and night often indicate detrusor instability, while normal early morning volumes with reduced and variable day volumes may indicate psychosomatic causes or be associated with genuine stress incontinence, when the patient voids urine more frequently to avoid stress leaks with a larger bladder volume.

Conclusion Frequency volume charts are a very useful way of augmenting the symptom history and of engaging the patient in trying to overcome lower urinary tract symptoms.

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