The Study Of Dynamic MRI Combine With 3D HR-ARM In The Evaluation Of Defecation Dysfunction After Anus-preserving Operation Of Low Rectal Cancer

Objective Apply pelvic dynamic MRI and defecography,combining 3D high resolution anorectal manometry(3D HR-ARM),to provide comprehensive,intuitive,non-invasive and repeatable imaging preoperative assessment for low rectal cancer patients which determine to do the anus-preserving operation.Analyse the mechanism of LARS after the anus-preserving operation from the morphology and dynamics.To find the correlation between imaging features and changes of anorectal dynamics,provide a comprehensive,intuitive,convenient and economical imaging technique for instituting proper clinical treatment plan.Materials and methods A total of 42 patients who were diagnosed as low rectal cancer and determined to do the anus-preserving operation from April 2016 to January 2017 in Tianjin Union Medical Center were included in this study.All patients undertook rectal palpation,colonoscopy,routine and dynamic MRI,defecography and 3D HR-ARM examination preoperatively.All patients performed surgical excision a week after those examinations,then getting pathologic examination.20 patients who were diagnosed as LARS after a three-month follow-up were included in case group,all patients reexamined pelvic dynamic MRI and 3D HR-ARM examination.20 healthy adult volunteers were included in control group,and all the volunteers undertook pelvic routine and dynamic MRI.Another 110 asymptomatic adult volunteers’ 3D HR-ARM examination data were collected to analyse.Compared the preoperative pelvic MRI image findings with rectal palpation,colonoscopy and pathologic findings,the Intraclass Correlation Coefficient and Kappa Test were used to analyse the consistency and correlation.Chi-square test was used to calculate diagnostic accuracy,sensitivity,specificity,positive predictive value and negative predictive value of pelvic MRI.The general linear model(GLM)univariate analysis was used to compare the differences of preoperative every measurement indicator between the case group and control group.Paired T test was used to compare the differences of every measurement indicator between the preoperative defecography and pelvic dynamic MRI,also between the preoperative and postoperative in case group.Pearson Correlation Coefficient was used to analyse the correlation between pelvic dynamic MRI findings and 3D HR-ARM changes.Results(1)A good consistency was found among pelvic MRI,rectal palpation and colonoscopy for measuring the distance between lower edge of tumor to anal verge(R=0.721,P<0.01).Compared pelvic MRI with pathologic(or colonoscopy)findings,a moderate consistency was found for measuring the rate of tumor size and rectal circumference(r=0.661,P<0.01),the overall accuracy was 83.33%.Pelvic MRI had high accuracy for tumor T and N staging,the overall accuracy were 88.10% and 85.71% respectively,and found a good consistency with pathologic findings(Kappa=0.729,P<0.01;Kappa=0.743,P<0.01).(2)Comparison of dynamic MRI findings,the preoperative M line on resting phase and defecation phase,IAS-T on lifting phase of LARS patients were all larger than those of control group(all P<0.05).The postoperative ARA on three phases of LARS patients were larger than preoperative results,but PR-T and EAS-T were less than preoperative results(all P<0.05).(3)On preoperative defecography of LARS patients,the ARA on lifting phase and the DUAC on defecation phase were larger than normal reference value.Compared preoperative defecography of LARS patients with pelvic dynamic MRI,the differences of ARA was not statistically significant,meanwhile,there was no significant correlation between M line and DUAC(both P>0.05).(4)Comparison of 3D HR-ARM changes,the preoperative maximum resting pressure(Mx RP),mean resting pressure(MRP),high-pressure zone(HPZ)length and maximum squeeze pressure(MSP)of LARS patients were all larger than those of normal reference value,however,the intrarectal pressure(IRP),rectoanal pressure differential(RAPD),initial defecation threshold(IDT)and maximum tolerance threshold(MTT)were all less than those of normal reference value(all P<0.05).The postoperative anal relaxation rate(ARR),first sensation threshold(FST),IDT and MTT were all less than those of normal reference value(all P<0.05).RAIR was less than 40 cc,the value was in the normal range both before and after surgery(15.79±10.17 cc and 13.68±6.84 cc respectively).(5)The postoperative Mx RP,MRP,HPZ length,MSP,FST,IDT and MTT were all less than those of preoperative results,however,the postoperative intrarectal pressure(IRP)and rectoanal pressure differential(RAPD)were larger than those of preoperative results(all P<0.01).(6)Analysed correlation of preoperative dynamic MRI and 3D HR-ARM,the distance between lower edge of tumor to anal verge was negatively correlated with MTT(r=-0.606).On lifting phase,ARA were negatively correlated with Mx RP and MSP(r=-0.722,r=-0.616),H line was negatively correlated with MSP(r=-0.620),M line were negatively correlated with FST and IDT(r=-0.545,r=-0.803),PR-T was positively correlated with IDT(r=0.794),EAS-T was negatively correlated with ARR(r=-0.609)(all P<0.05).(7)Analysed correlation of postoperative dynamic MRI and 3D HR-ARM,on lifting phase,M line was positively correlated with IDT(r=0.727),PR-T was positively correlated with HPZ length(r=0.738),IAS-T were negatively correlated with HPZ length and RAPD(r=-0.680,r=-0.729)(all P<0.01).Conclusion(1)Pelvic dynamic MRI has high accuracy and good consistency with rectal palpation and colonoscopy,it can provide comprehensive,quantitative and repeatability imaging informations for preoperative evaluation of low rectal cancer and postperative evaluation of anorectal function.(2)Dynamic MRI has good consistency with defecography.It can compensate the low resolution of soft tissue on defecography and provide a more secure and convenient method for evaluating anorectal function.(3)Dynamic MRI and 3D HR-ARM examinations find that LARS patients had good ability of controlling defecation before surgery,however,obvious pelvic floor relaxation and decrease of rectal sensation function were found.Furthermore,puborectalis and anal sphincter function were significantly decreased after surgery,and rectal sensation function weakened more significantly.It shows that as possible to avoid such muscle injury during the operation and as early to strengthen recovery treatment of diseased muscle function after operation are particularly important for patients with LARS.(4)Dynamic MRI technique not only can reflect the dynamic changes of anorectal intuitively,but also has obvious relevance with 3D HR-ARM.It will provide a more efficient,economical,convenient and visual new imaging idea.