RESUMO
Objective To evaluate the development of the sphincter muscle complex(SMC)and defecation function in pediatric patients with congenital anorectal malformations(ARM).Methods A total of 64 children underwent MRI,among whom 39 were patients with ARM,and the others were patients without ARM undergoing MRI because of other dieases.The dimensions of the SMC in different planes were evaluated with different sequences and coils.The relationship between the SMC development and the defecation function was investigated.Results In control group,the absolute value of SMC width was (3.63?0.22)mm,which had a high correlation with age(r=0.998,P0.05).The SMCs in intermediate ARM patients[muscle index(MI)=0.47?0.05]and low ARM patients(MI=0.49? 0.05)were well developed.The SMCs in a portion of patients with high ARM(MI=0.28?0.06)were poorly developed,when MI≤0.18,anorectal contraction pressurewas significantly lower(t=3.55, P0.18[(0.85?0.20)vs(2.24?1.02)kPa].The length of anal canal with high-pressure[(10.88?3.64)vs(20.26?4.34)mm]was shorter(t=5.18,P0.18,the anorectal angle was less than 90 degrees,and normal continent function was found in 21 of 23 cases(91%).Conclusion MRI can be employed to evaluate the development of SMC in patients with ARM,MI was an objective criteria to evaluate the development of SMC.When MI≤0.18, maldevelopment of SMC will be highly suspected.