A systematic review of preoperative radiological factors associated with the development of low anterior resection syndrome (LARS)

The aim of this systematic review is to summarise the available evidence for radiological changes associated with postoperative low anterior resection syndrome (LARS). A literature search was undertaken for all studies focusing on preoperative radiological predictors of postoperative LARS. Articles were selected from MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL) databases up to October 2024. Eighty-four articles were screened: eighty-one were excluded and three were included in the analysis. All included studies focused on preoperative Magnetic Resonance Imaging (MRI) already performed as part of the oncological assessments, no study examined ultrasound or defecography. Authors retrospectively selected patients that underwent LAR, screened them with the LARS score, and reviewed preoperative MRI images with specific softwares in order to find radiological characteristics associated with LARS. Results showed that particular anatomical characteristics were present in patients that subsequently developed major LARS: the volume of the pubococcygeal + iliococcygeus muscles in 27 LARS patients out of 46 LAR (odds ratio-OR 14.7, 95% CI 1.7-128.3; p = 0.02), the thickness of the anorectal joint in 136 LARS out of 255 LAR preceded by neoadjuvant chemoradiotherapy (OR 0.653, 95% CI 0.565-0.756; p = 0.001) and the mesorectal/pelvic volumes in 135 LARS out of 236 LAR (Cox Regression analysis, p = 0.0017 and p = 0.0001 respectively). Pelvic floor musculature is a factor, among the others, that contributes to LARS. Future prospective studies need to validate these retrospective results, further delineate its influence, and investigate the potential contribution of other radiologic investigations (ultrasound and defecography) in this setting.