CHAPTER 3 Urodynamic procedures

INTRODUCTION

Symptomatic evaluation of urinary tract dysfunction is difficult since the bladder often proves to be an ‘unreliable witness’, not only because of subjective bias from both the patient and the clinician; but also because there is considerable overlap between the symptoms from different disorders. Urodynamic techniques are objective investigations developed to clarify these symptoms. The term urodynamics encompasses a variety of complementary techniques of varying complexity (Table 3.1).

Table 3.1 Urodynamic techniques.

Urodynamic techniques
Complexity of technique	Technique
Simple – voiding diary	Micturition/time chart Frequency/volume chart Bladder diary
Simple – investigation	Pad testing Uroflowmetry ± ultrasound residual Ultrasound cystodynamogram Intravenous urodynamogram
Pressure/flow studies (Chapter 4)	Cystometry Leak point measurements Video urodynamics Ambulatory urodynamics
Complex – investigation	Urethral pressure measurement Neuro-physiological investigation Upper tract urodynamics (Whitaker test)

In this chapter the indications and methodology for these various techniques will be discussed along with introducing common clinical findings. The majority of invasive urodynamic investigations are pressure/flow studies and these will be discussed in detail in the next chapter (Chapter 4). More detailed discussion of common lower urinary tract disorders and associated urodynamic findings will occur in later chapters.

INDICATIONS FOR URODYNAMIC ASSESSMENTS

Only a good understanding of the various techniques including methodology, limitations and specific indications will allow the clinician to choose an appropriate test. In many cases a number of investigations may be necessary to answer all the clinical questions or further investigations may be required if the first investigation was unhelpful or presents a new avenue for investigation.

Before embarking on any urodynamic investigation the following should be considered:

• Is there a clear indication for the chosen test?

Will it aid in diagnosis?

Will it aid in making management decisions?

• Is this the most appropriate test?

Would a simpler test answer the clinical questions?

Is a more complex test more likely to answer all the clinical questions?

• Are there appropriate local facilities and expertise to perform the chosen test?

• Is the most appropriate person, with an understanding of the patient’s individual condition performing the test?

STANDARDIZATION AND QUALITY CONTROL

All urodynamics should be performed in a standardized manner; this not only maintains the quality of the data, but also allows for comparison of the results if a patient has a repeat investigation. In addition a standardized technique and recording of the data using recognized terminology allows the accurate exchange and comparison of information for both clinical and experimental purposes. The official terminology suggested by the International Continence Society (ICS) is used throughout this book. However investigations must still be tailored for individual patients so that the clinical questions are answered thoroughly without undue time spent on obtaining clinically irrelevant data.

Maintaining the quality of any study also requires that all equipment is appropriately set up and regularly calibrated with sufficient working knowledge to ‘troubleshoot’ any problems encountered during an investigation.

In all cases precise measurement and complete documentation must be coupled with accurate analysis and critical reporting of the results. However, it must be borne in mind that whilst these are objective tests that can be standardized to a high degree, there remains a significant subjective element in the interpretation of the results. Urodynamics is not an exact science!

AIMS OF URODYNAMIC INVESTIGATIONS

The principal aim of any urodynamic assessment is to reproduce the symptoms whilst obtaining physiological measurements, so as to determine the pathophysiology underlying the symptoms.

Both the precise nature of the condition and the severity can be established, thus allowing the clinician to understand the clinical implications and plan further appropriate management.

In most cases the indications for urodynamic investigation are clear and its appropriate application is essential to the modern practice of urology, gynaecology, and any specialties dealing with the management of lower urinary tract dysfunction.

VOIDING DIARIES

Voiding diaries are the simplest of all urodynamic assessments, yet their value is often overlooked. They provide an important natural urodynamic record of bladder function.

Indications and aims

Voiding diaries are simple, non-invasive tools that are frequently part of the initial evaluation of patients complaining of LUTS, particularly those who have storage symptoms such as increased urinary frequency and incontinence.

They give an indication of the voiding pattern, the severity of symptoms and they add objectivity to the history. They may also give an indication of the impact on the patient’s life and may highlight ‘coping strategies’ that the patient has adopted to help manage their symptoms. Voiding diaries are also useful in identifying pathophysiology of renal origin such as abnormal production of urine related to the circadian rhythm.

A number of different diaries have been defined by the ICS:

• Micturition time chart – records only the times that voids occur with no volumetric data.

• Frequency/volume chart (FVC) – records the time and volume of each micturition.

• Bladder diary – records the time and volume of each micturition and may also include other data such as incontinence episodes, pad usage, fluid intake and urgency (Table 3.2).

Table 3.2 Bladder diary. Recording volume and time of each void, fluid intake, pad usage and incontinence episodes (W). Patients also record waking/retiring time to allow calculation of nocturia.

Method and standardization

The patient is asked to record as accurately as possible the time of events such as voids and incontinent episodes on the chart and to measure the volume voided using a graduated container (jug). They are also asked to record the time they are awake and asleep. Patients must be instructed to continue their normal activities during the course of the assessment, so as to obtain an accurate representation of their normal lower urinary tract function. The ICS has recommended that voiding diaries are performed for at least 24 hours, although in practice a period of 3–7 days is usually chosen. Most patients find them acceptable for use over short periods.

Frequent findings

• Normal frequency and voided volumes.

• Increased frequency and normal volumes – therefore an increased 24-hour production of urine, suggesting a high fluid intake. This may be related to diabetes mellitus or diabetes insipidus but is more usually habitual, especially with the increasing popularity of high fluid diets.

• Reduced volumes with minimal variation in the volume voided – suggesting a bladder wall pathology such as bladder pain syndrome/painful bladder syndrome/interstitial cystitis or carcinoma in situ (Note – An anatomical capacity measured under general anaesthesia will confirm the presence of a reduced bladder capacity due to anatomical reasons such as fibrosis or a contracted bladder. A reduced anatomical capacity often implies a low likelihood of response to conservative therapeutic modalities).

• Reduced volumes with variation in the volume voided – suggestive of underlying detrusor overactivity as the bladder contracts at variable degrees of distension before maximum capacity, erroneously informing the patient that it is full; resulting in urinary frequency and low and variable voided volumes.

• Increased nocturnal production – (nocturnal polyuria), suggestive of cardiac failure, dependent fluid shifts in the supine position, hormonal fluid balance abnormality or idiopathic in origin. This is not a urological condition.

Voiding diaries must not be over-interpreted, but should be used in combination with other forms of urodynamic and urological assessment (Table 3.3).

Table 3.3 Urodynamic parameters measured by voiding diaries.

Urodynamic parameters measured by voiding diaries
Daytime frequency	Number of voids recorded in waking hours
Nocturia	Number of voids recorded during sleep hours with each void preceded and followed by sleep
24-hour frequency	Total number of awake and sleep voids during a specified 24-hour period
24-hour production	Total volume of urine voided during a specified 24-hour period
Polyuria	Voiding of more than 2.8 litres in 24 hours
Nocturnal urine volume	Total volume of urine voided during sleep hours, excluding the last void before sleeping but including the first void on waking
Nocturnal polyuria	When an increased proportion of the 24-hour production occurs at night, usually >33% (but age-dependent)
Maximum voided volume (replaces the term ‘functional volume’)	The largest volume voided during a single micturition. Particularly important when deciding how much to fill the bladder during pressure/flow urodynamics, to prevent overfilling
Pad usage	Number of pads used during a specified period
Frequency of incontinence episodes	Number of incontinence episodes during a specified period
Frequency of urgency episodes	Number of urgency episodes during a specified period
Fluid intake	Volume of fluid ingested during a specified period