Hypothesis / aims of study
Video urodynamics utilises fluoroscopy to provide diagnostic evaluation of patients with lower urinary tract dysfunction. However, exposure to radiation is an inevitable consequence of this. We are conscious that ionising radiation has the potential to lead to malignancy, with the smallest dose of radiation having the potential to increase this risk due to the linear-no-threshold risk model for ionising radiation.
Both the International Commission on Radiation Protection (ICRP)(1) and the Ionising Radiation (Medical Exposure) Regulations (IRMER)(2) advise dose justification, optimisation and limitation in order to keep radiation exposure “as low as reasonably achievable” (ALARA). Whilst these ‘ALARA’ principles are essential, the lack of reference levels, allows for subjective interpretation and variation in practice. There are no reference levels for radiation exposure during video urodynamics studies.
Our aim was to review exposure to radiation during video urodynamics in our department. We wanted to determine whether there was a significant difference between radiation exposure in men and women undergoing video urodynamics. We also wanted to compare radiation exposure to that of other common urological procedures, to understand whether this was acceptable and reasonable.
Study design, materials and methods
A prospective database of all urodynamics procedures was interrogated for video urodynamic procedures between February 2018 and February 2019. The department of radiology cross referenced patient identification numbers with their records to find the dose area product and fluoroscopy for each test performed. Data were analysed with Microsoft Excel.
A total of 39 patients, 31 female and 8 male, were identified to have had video urodynamics at our institution. Patients were excluded if data was not recorded. After exclusion, 32 patients, 26 female and 6 male data were analysed. For the group as a whole, the mean dose area product of radiation was 4.93 Gy.cm2 and mean fluoroscopy time was 57.6 seconds. In female patients the mean dose area product of radiation exposure was 5.1 Gy.cm2 with a mean fluoroscopy time of 55.2 seconds. In male patients the mean dose area product was 4.3 and mean fluoroscopy time was 67.1 seconds. There was no significant difference between these two groups (p 0.52). The overall mean dose area product and fluoroscopy time was compared with those of common urological procedures (3).
Interpretation of results
A multicentre comparison of radiation exposure for common urological procedures has been used to propose reference levels for radiation exposure (3), with the aim of protecting the patient from undue over exposure. These reference levels are for ureteric stent insertion or replacement (2.3 Gy.cm2/49 seconds, ureteroscopy (2.8 Gy.cm2/57 seconds and percutaneous nephrolithotomy (PCNL) 24.1 Gycm2 /431 seconds (3). Video urodyamics in our centre at 4.93 Gy.cm2 /57.6 seconds exposes patients to almost double the radiation of stent insertion/replacement and ureteroscopy, despite similar fluoroscopy exposure times. Video urodynamics reassuringly exposes patients to less radiation than PCNL.
When taking the decision to refer a patient for video urodynamics, or when performing video urodynamics, the clinician should be mindful of the significant radiation exposure of the procedure. This is almost double the exposure expected in stent based procedures and ureteroscopy in a recent series.
The disproportionate radiation exposure to fluoroscopy time suggests that better screening practice may help to reduce total radiation exposure, such as avoiding continuous screening where possible, marking areas of interest on the patient or drapes to reduce unnecessary exposure and changing machine settings to low-dose settings, fewer frames per minutes, tight collimation to the area of interest and optimizing the location of the image intensifier.
In the video urodynamics setting is perhaps a more challenging environment in which to use ionising radiation when compared to common urological procedures performs under general anaesthetic. In video urodynamics the patient in fully conscious, undergoing physiological stress to try to replicate their symptoms and is a test that carries a level of stigma with it. It may be that these challenges are reflected in the results.