A systematic review and meta-analysis of preoperative MRI-based pelvimetry in predicting surgical difficulty in rectal cancer: Implications for personalised surgical planning.

Background: Magnetic resonance imaging (MRI)-based pelvimetry has been investigated for predicting surgical difficulty in total mesorectal excision (TME) for rectal cancer. However, heterogeneity in pelvimetric parameters, surrogate outcomes, and study design has resulted in inconsistent evidence. This systematic review aimed to synthesise the evidence on commonly used MRI parameters and difficulty surrogates and assess their methodological robustness and clinical relevance.

Methods: PubMed, Embase, and the Cochrane Library were systematically searched through December 2025 for studies evaluating preoperative MRI pelvimetry in patients undergoing TME for rectal cancer. Outcome parameters were surrogate measures of surgical difficulty, including operating time, intraoperative blood loss, conversion to open surgery, pathological quality metrics, and postoperative complications. Risk of bias was assessed using the Risk of Bias in Non-randomised Studies of Exposures (ROBINS-E) tool. This systematic review and meta-analysis was reported in accordance with the PRISMA 2020 statement and prospectively registered (PROSPERO: CRD420261287153).

Results: Thirty-six studies comprising 8,364 patients were included. Common parameters included sagittal measurements and axial interspinous distance (ISD) and intertuberous distance (ITD). Definitions of surgical difficulty varied substantially. ROBINS-E identified some concerns in 30 studies, a high risk of bias in five, and insufficient information in one. Meta-analysis of six studies (n = 769) showed that shorter ISD (mean difference [MD] -5.13 mm, 95% CI -6.61 to -3.65; p < 0.001; I2 = 0%) and ITD (MD -7.32 mm, 95% CI -10.24 to -4.39; p = 0.004; I2 = 0%) were significantly associated with surrogate measures of surgical difficulty.

Conclusions: MRI-based pelvimetry, particularly ISD and ITD, may help predict surgical difficulty in TME. However, methodological heterogeneity limits broader quantitative synthesis and highlights the need for standardised pelvimetric protocols.