Hypothesis / aims of study
Following spinal cord injury (SCI), disruption to neuronal pathways to the bladder can lead to development of neurogenic lower urinary tract dysfunction (NLUTD). The goal of good bladder management is to ensure safe storage pressures and efficient voiding to protect the upper tracts. Videourodynamics (VCMG) is a functional test of the lower urinary tract in which pressure, capacity and flow data are simultaneously combined with real-time fluoroscopic imaging of the upper and lower urinary tract. The NICE guidelines for management of NLUTD state that regular surveillance VCMGs should be performed in patients at high risk of upper tract damage. This may constitute a significant radiation exposure risk over a lifetime for which patients need to be consented. The guiding principle for all examinations requiring ionising radiation is ALARP – ‘as low as reasonably practicable’. The aim of this audit was to provide useful information for those requesting and performing VCMGs on exposure levels for people with SCI undergoing VCMG as part of their long-term bladder management.
Study design, materials and methods
Dose Area Product data for VCMG examinations between March 2021-March 2022 were extracted from the electronic database. Age, sex, level of injury and bladder management technique were recorded. During a standard VCMG investigation, single shots are taken of the bladder at infused volume (IV) of 30 ml and repeated if required during filling. Screening occurs during stress coughs at an IV of 75 ml and at end fill volume (EFV). Screening is also undertaken during the voiding phase if appropriate. Additional screening is undertaken if vesico-ureteric reflux is noted during the test.
Interpretation of results
The greatest DAP were seen in the patients who voided due to the additional screening time during the voiding phase, compared to non-voiders. 16/270 patients had a DAP > 100 cGycm2. 14/16 of these were voiders. The remaining 2 patients had an IDUC, however, one of them had reflux so additional imaging of the kidneys and ureters was undertaken. Other factors affecting absorbed dose which were not analysed include body weight, height, fluoroscopic kV and fluoroscopy time. For comparison, the average DAP for an Abdominal AP x-ray is 260 cGycm2 and for an IVU 1400 cGycm2. The NDRL for Micturating Cystourethrogram is 700 cGycm2