Consensus of risk factors and effectiveness of current management of low anterior resection syndrome (LARS) in rectal cancer with preservation of the anal sphincter: state of the art

Introduction: Low Anterior Resection Syndrome (LARS) is the main functional sequela after sphincter-preserving rectal surgery. It affects 40–45% of patients at ≥12 months and impairs quality of life. This work synthesizes risk factors and therapeutic effectiveness to guide personalized decision-making.Methods: We conducted a PRISMA systematic review (2017–2024) of MEDLINE, EMBASE, and Cochrane with dual screening and duplicate data extraction. We included adults who underwent low anterior resection with validated measures of LARS and/or quality of life. Risk of bias was assessed (RoB 2, ROBINS-I/NOS, AMSTAR-2) and certainty was graded with GRADE. A qualitative synthesis and vote counting were performed.Development: Nineteen studies were included: 2 trials/follow-ups, 7 observational studies, 6 systematic reviews/meta-analyses, and 4 guidelines/narratives. Neoadjuvant radiotherapy was associated with higher LARS (OR ≈3) and worse quality of life. Other factors included ultralow anastomosis, total mesorectal excision, and anastomotic leak. Transanal irrigation (TAI) reduced early stool frequency and tended toward a lower LARS score at 12 months in a randomized controlled trial; in therapeutic cohorts it reduced LARS and incontinence. Sacral neuromodulation showed improvement in refractory cases, with low–moderate certainty of evidence. Pelvic floor rehabilitation and pharmacotherapy provided symptomatic relief with limited support. Certainty was moderate for the impact of radiotherapy and the usefulness of TAI, and low for the remainder.Conclusions: LARS was common and modifiable. We recommended preoperative counseling on functional risk, surgical prevention, early TAI in high-risk patients, a stepped, phenotype-based approach with psychological support, and neuromodulation for refractory cases, with longitudinal follow-up to tailor treatment using more patient-relevant metrics.