2.3: Urodynamic Investigations

What is meant by the term Urodynamic investigations?

In 1970 Bates coined the expression that ‘the bladder often proves to be an unreliable witness’, meaning that the presenting symptoms of the patient and the eventual diagnosis of the problem are often at variance. In 1972 Moolgaoker stated that ‘urinary symptoms in the female do not form a scientific basis for treatment’.

Urodynamic tests have been developed to confirm the underlying diagnosis in a patient complaining of symptoms of urinary incontinence. These tests identify the etiology of the problem and elucidate its pathophysiological mechanism. Their use is sometimes debatable, since grade A evidence supporting the general use of urodynamics in the investigation of incontinence, is not available.

The most basic form of urodynamic testing which is used in present day practice consists of:

1. Uroflowmetry (otherwise known as a ‘free flow measurement’

2. Multichannel urodynamics which involve filling and voiding cystometry (the latter being a so – called ‘pressure – flow’ study).

Depending on the sophistication of the apparatus used, either a leak – point pressure measurement, or urethral pressure profilometry may be performed additionally as a test of urethral function. Urodynamic testing can either be static or ambulatory.

Videocystourethrography is used in advanced centres and is the gold standard of the investigation of female urinary incontinence. It involves contrast media and screening radiology superimposed upon conventional cystometry to provide an accurate diagnosis. This modality is not widely available.

Increasingly, ultrasound imaging is also being used to measure both bladder neck descent and bladder wall thickness. Electromyography and cystoscopy are adjuncts to urodynamics in complex patients with atypical pathology.

The measurement of urethral resistance pressure has recently been pioneered. This does have potential as a diagnostic tool of the future. However, at present its widespread use as a routine urodynamic tool is questionable and it should only be used in research studies aimed at clarifying its value.

Basic tests which should be performed on patients prior to urodynamic testing include a urine microscopy and culture, and a measurement of residual urine volume, either by catheter or ultrasound. A bladder diary (frequency / volume chart) is

also a necessary aid to diagnosis. The latter has been shown to provide valuable information on the patient’s voiding pattern and functional bladder capacity, as well as giving an indication of leakage episodes.

It can be said that most urodynamic tests are expensive, time consuming and invasive (involving catheterization of the patient). They also require considerable expertise and access to sophisticated equipment. There should therefore be sound motivation for their use as a diagnostic tool.

Clinical Indications for Urodynamics Investigations

There are many etiological factors leading to urinary incontinence in women. Certainly the most common problems are urodynamic stress incontinence due to urethral sphincter weakness or bladder neck hypermobility, and detrusor overactivity leading to incontinence (in most cases ‘urge incontinence’). Other causes of incontinence include fistulae, urethral diverticulae, urethral instability, the urethral syndrome and also the contributory effect

of urinary tract infection. It must be emphasized that many of these conditions may mimic the symptoms associated with stress incontinence and destrusor overactivity.

A cough – induced bladder contraction causing leakage may be confused with stress incontinence (so called ‘stress – induced instability’).

There may be serious sequelae if a patient suffering from urinary incontinence is not adequately evaluated and an incorrect diagnosis is made. The most serious of these is inappropriate surgery. Failure to recognize concomitant detrusor overactivity and / or voiding dysfunction may also affect the outcome of appropriate surgery.

Table 1 lists the most important indications for urodynamic studies.

Table \(\PageIndex{2.3.1}\): Indications for urodynamic studies

1.	Prior to surgery
2.	Failed medical or surgical treatment
3.	Complex symptomatology
4.	Neurological dysfunction
5.	Voiding dysfunstion
6.	Medico – legal cases

Clinical Diagnosis versus urodynamic diagnosis

Over the past 35 years there have been ongoing discussions in the literature on how best to evaluate patients with incontinence. The accurate identification of patients with SUI has received considerable attention

The accuracy of history alone

Most of the early papers looked at the discriminatory value of a pure history of either stress incontinence or detrusor instability. Symptoms alone were used to make a diagnosis before patients were subjected to confirmatory cystometry. Most of the earlier studies had relatively low numbers of patients. In summary, it is clear from the majority of studies that a history of incontinence alone is not enough to enable a clinician to make an accurate diagnosis for a decision on whether or not to embark on stress incontinence surgery. The symptom of stress incontinence may be very sensitive, but is so nonspecific as to render it of little diagnostic value.

History is best used as a guide to the subsequent evaluation process and to serve as a measure of disease severity.

History, clinical examination and basic tests

In the ongoing search for an uncomplicated and cost – effective approach to the pre – operative evaluation of a patient for stress incontinence surgery, several authors looked at other parameters which could prove useful.

In summary the addition of other clinical parameters and simple office tests do enhance the sensitivity of a history. However, the various authors still found the combination inadequate for a reliable diagnosis and most felt that additional research was warranted.

In South Africa, Urogynaecology as a subspeciality is still in its infancy. Treatment decisions in female urinary incontinence management are mostly made on clinical judgment. There are very few management protocols in place and this is an area which urgently requires development, particularly at specialist level.

Medical practice is increasingly becoming dogged by litigation and practitioners have to be able to show that they have their patient’s best interest at heart by backing

up clinical diagnosis with special investigations.

In the larger centres in SA there are facilities available for performing urodynamic studies but these are mostly underutilised. They are often also run by staff who are not properly trained to provide good quality results and interpretation.