静态及动态MRI评价初产妇经阴道分娩后6个月肛提肌损伤与盆腔器官脱垂的关系

Correlation between levator ani muscle injury and pelvic organ prolapse in primiparous women 6 months post vaginal delivery： a static and dynamic MRI study

目的采用静、动态MRI观察经阴道分娩后6个月初产妇盆腔器官位置和肛提肌的形态和功能，探讨肛提肌损伤与盆腔器官脱垂（POP）的关系。方法前瞻性收集经阴道分娩后6个月的初产妇51例作为产妇组，未孕、未产的35名女性志愿者作为对照组。所有受试者均行静态及动态盆底MRI检查。参照MRI诊断POP的标准将产妇组分为产妇POP组及产妇正常组。在静态MRI上行肛提肌损伤评分，根据双侧肛提肌总分判断损伤程度（无损伤、轻度损伤及重度损伤）；测量动态和静态MRI上肛提肌以下指标，包括耻骨联合下缘至直肠后壁肛直肠连接处的距离（H线）、H线末端至耻骨尾骨线的垂线距离（M线）、肛提肌裂隙（LH）、提肛板角（LPA）、双侧髂骨尾骨角（1eA）。采用独立样本t检验或Mann．Whitney检验比较产妇POP组与产妇正常组间动态MRI肛提肌测量指标间的差异，采用Fisher确切概率法比较产妇组与对照组、产妇POP组与产妇正常组问肛提肌损伤程度的差异。结果产妇组51例中，耻骨直肠肌无损伤44例、轻度损伤5例、重度损伤2例，髂骨尾骨肌无损伤32例、轻度损伤10例、重度损伤9例；对照组35例中，耻骨直肠肌均无损伤，髂骨尾骨肌无损伤32例、轻度损伤2例、重度损伤1例。2组间耻骨直肠肌损伤程度的差异无统计学意义（P=-0．203），髂骨尾骨肌损伤程度的差异有统计学意义（P〈0．05）。产妇POP组24例中，耻骨直肠肌无损伤20例、轻度损伤2例、重度损伤2例，髂骨尾骨肌无损伤14例、轻度损伤6例、重度损伤4例；产妇正常组27例中，耻骨直肠肌无损伤24例、轻度损伤3例，髂骨尾骨肌无损伤18例、轻度损伤4例、重度损伤5例。耻骨直肠肌、髂骨尾骨肌损伤程度的差异均无统计学意义（P值分别为0．588和0．559）。产妇POP组和产妇正常组用力状态下LH分别为（6．7±1．1）、（5．0±0．6）cm，用力状态下LHA分别为（41．6±12．6）、（24．2±5．5）cm^2，差异均有统计学意义（P值分别为0．042和0．004）。其余静态和用力下肛提肌指标差异均无统计学意义（P均〉0．05）。结论经阴道分娩会造成初产妇的不同程度肛提肌损伤，发生POP的初产妇伴肛提肌功能减弱。

Objective To observe the location of pelvic organs, the morphology and function of levator ani muscle （LAM） in primiparous women post vaginal delivery at 6 months postpartum using static and dynamic MRI, and investigate the correlation between LAM injury and pelvic organ prolapse （POP）. Methods A perspective analysis of static and dynamic MRI was performed in fifty-one prlmiparous women post vaginal delivery at 6 months postpartum and thirty-five nulliparous women without experience of pregnancy and delivery as control group from June 2014 to January 2015. Previous pregnancy and abortion history, previous pelvic surgery and pelvic mass diseases were excluded. Cases with pelvic floor dysfunction symptoms were excluded from the control group. All of the women underwent static and dynamic MRI. The primiparous group was divided into two groups on presence or absence of POP on MRI findings： primiparous POP group and primiparous control group. The levatorani scoring system based on static MRI was used to characterize morphological changes of LAM into none, minor and major injury by the total score of bilateral LAM. A series of parameters including H line （the distance between the inferior margin of pubic symphysis to anorectal junction）, M line （the perpendicular distance between the distal end of H line to pubococcygeal line）, levator plate angle （LPA）, iliococcygeal angle （ICA）, and levator hiatus length and area were measured on static and dynamic MR images. Fisher exact test was performed to compare difference in distribution of the LAM injury between the primiparous group and control group, as well as the primiparous POP group and primiparous control group. Independent sample t test or Mann-Whitney test was used to compare difference in LAM parameters between the primiparous POP group and primiparous control group. Results In the 51 cases primiparous group, 44 cases showed none injury, whilst 5 cases with minor and 2 cases with major injury in the puborectal muscle. Thirty two cases showed none injury, whilst 10 cases with minor and 9 cases with major injury in the iliococcygeal muscle. In the 35 cases control group, none injury was shown in puborectal muscle, whilst 32 cases with none, 2 cases with minor and 1 case with major injury in the ilioeoccygeal muscle. There was no significant difference in the puborectal muscle injury between the two groups （P=-0.203）, and there was significant difference in the iliococcygeal muscle injury between the two groups （P〈0.05）. In the 24 cases primiparous POP group, 20 cases showed none injury, whilst 2 cases with minor and 2 cases with major injury in the puborectal muscle. Fourteen cases showed none injury, whilst 6 cases with minor and 4 cases with major injury in the iliococcygeal muscle. In the 27 cases primiparous control group, 24 cases showed none and 3 cases with minor injury in the puborectal muscle, whilst 18 cases with none, 4 cases with minor and 5 cases with major injury in the iliococcygeal muscle. There was no significant difference in the puborectal muscle injury and iliocoecygeal muscle injury between the two groups （P=0.588 and 0.559, respectively）. The LH during Valsalva status in primiparous POP group and primiparous control group were （6.7±1.1） and （5.0±0.6） cm, respectively, whilst the LHA was （41.6±12.6） and （24.2±5.5） cm^2. There were significant difference between the corresponding groups （P=0.042 and 0.004, respectively）. There was no significant difference between the corresponding groups of the other LAM parameters on static and dynamic MRI （all P〉0.05）. Conclusion Vaginal delivery may cause various degrees of LAM injury, the LAM functional deficiency were observed in primiparous women combined with POP.