Micro-enema prior to prostate MRI reduces rectal gas and gas-related artefacts improving image quality

Abstract

Purpose There are conflicting results in the literature regarding bowel preparation prior to prostate Magnetic Resonance Imaging (MRI) and its effect on image quality. Our aim was to determine whether the administration of a micro-enema immediately prior to MRI is associated with a reduction in rectal gas, gas related artefacts and an improvement in image quality. Method This retrospective analysis enrolled 171 patients who underwent multiparametric 3T prostate MRI at our institution between January 2021 and September 2022. 86 patients received a micro-enema, and a further 85 patients did not. Two fellowship trained abdominal radiologists were blinded and independently reviewed each prostate MRI, recording scores on a dedicated scoring sheet. The quality of T2 weighted (T2W), diffusion weighted (DWI), and dynamic contrast enhancement (DCE) images were assessed according to standardised scales supported in the literature. In addition, gas related artefacts and rectal gas level were examined. An independent-samples Mann-Whitney U Test was performed, comparing the median score between micro-enema and no micro-enema groups. Spearman’s correlation was used to determine the strength of relationship between variables. A quadratic weighted Cohen’s Kappa and percent agreement were used to assess inter-observer agreement. Results Image quality was improved in those who received the micro-enema compared to those who did not according to the visual grading scale on the DWI sequence (median score 5 vs 4, p = < 0.001). PI-QUAL score and visual grading score for both the T2W and DCE images was not significantly different. Rectal gas level was lower in patients who received the micro-enema (median score 1 vs 3, p < 0.001), correlating with a lower score for gas-related artefacts (1 vs 2, p < 0.001) in this group. Correlation between rectal gas level and gas-related artefacts on DWI regardless of whether a micro-enema was given was strong (r_s = 0.707, p < 0.001). Correlation was moderate to strong between rectal gas level and image quality on DWI (r_s = -0.626, p < 0.001). There was only 1 (1.2%) borderline diagnostic or non-diagnostic DWI sequence in those who received the micro-enema, compared to 9 (10.6%) in those who did not (p = 0.009). Interobserver agreement was moderate for image quality on DWI, gas related artefacts and rectal gas level (weighted kappa values of 0.518, 0.488 and 0.525 respectively). Conclusions The administration of a micro-enema prior to prostate MRI is associated with a significant improvement in image quality on the DWI sequence. This is mediated through a reduction in rectal gas and gas related artefacts.