Abstract
Data quality and documentation of variance are key for urodynamics studies to be valid, and symptoms must be reproduced to be able to make a diagnosis. Accurate reporting requires knowledge of pathophysiological parameters and the ability to detect artefacts. If inaccuracies are discovered, they should be corrected contemporaneously. Spurious and inaccurate observations are known as artefacts. The Oxford dictionary defines artefacts as something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure.’
9.1 Introduction
Data quality and documentation of variance are key for urodynamics studies to be valid, and symptoms must be reproduced to be able to make a diagnosis. Accurate reporting requires knowledge of pathophysiological parameters and the ability to detect artefacts. If inaccuracies are discovered, they should be corrected contemporaneously. Spurious and inaccurate observations are known as artefacts. The Oxford dictionary defines artefacts as something observed in a scientific investigation or experiment that is not naturally present but occurs as a result of the preparative or investigative procedure.’
These occur because of pitfalls including:
failure to reproduce symptoms
observations normally indicating pathology occurring in the absence of disease
biological variability leading to false negatives
the wide variation within the physiological range of the normal population.
9.2 Factors Affecting Urodynamic Investigations
Several factors may influence the measurements recorded on the cystometrogram:
filling medium type, temperature and rate of infusion
catheter size
patient position
testing in an artificial environment
patient movement and external movement of the catheters
catheter blockages or expulsion
communication
inaccuracies in uroflowmetry
equipment (all equipment should conform to International Continence Society technical specifications)
9.3 Uroflowmetry Artefacts
Artefacts during uroflowmetry may arise owing to several factors, which can be broadly classified into two groups: extracorporeal and intracorporeal.
Extracorporeal causes include:
flow interference between the collecting funnel and flowmeter
movement of the stream across the funnel surface
momentum artefact due to the momentum of the stream
patient movement (Figure 9.1).
very low flow
time delay
Intracorporeal causes include:
rapid abdominal straining (Figure 9.2)
fast and rapid flow (Figure 9.3).
liquid density error leading to higher flow rates in dehydration.
Although the computerised reading shows a Qmax of 35.1 ml/s, manual assessment of flow using smoothed curve denotes the actual Qmax of 4 ml/s.
Figure 9.1 Uroflowmetry trace demonstrating changes owing to patient movement. The abrupt spike is recorded by the machine as the maximum flow rate (35.1 ml/s). This is an artefact and gives a falsely high maximum flow rate. The actual maximum flow rate in the region should be read as 20 ml/s.
Figure 9.2 Changes in uroflowmetry recording induced by rapid abdominal straining. The solid arrow on the curve drawn denotes the manually read maximum flow rate
Figure 9.3 Changes in uroflowmetry recording induced by fast and rapid flow; solid arrow on the curve drawn denotes the manually read maximum flow rate. Although the computerised reading shows a Qmax 50.3 ml/s, manual assessment of flow using smoothed curve denotes the actual Qmax 5 ml/s
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