The Applicational Value Of MRI In The Diagnosis On Perianal Fistulas And Comparison With Clinical Results

Part one:The preoperative MR diagnosis and classification of perianal fistulasObjective To explore the clinical applicational values of diffusion weighted imaging(DWI)combined with generic sequence in the preoperative assessment and classification of anal fistula with reference to surgical-pathologic findings.Methods 56 patients with pathology proven perianal fistulas were examined with routine MR sequence and axial DWI,in which routine scan sequences included axial T1 WI,T2WI and fat sequence T2 WI,coronal and sagittal fat sequence T2 WI.With surgical-pathologic results as the golden standard,the display rates from conventional sequences and conventional sequences combined with DWI of internal opening,external opening,primary tract,secondary tract and abscess were respectively analyzed and compared.According to the Park's classification,the series of cases were classified and the data were also compared with surgical findings.Results In the 56 cases,there were 7 simply anal fitulars and 49 complex ones that proved by the operational results.Besides of 9 cases of seldomly happened rectovaginal fistulas,according to the Parks classification,7 between-sphincteric,24 trans-sphincteric,none of extra-sphincteric,16 supra-sphincteric were diagnosed by MRI and the totally coincidental rate was 87.5%(49/56)with surgical comparing.Totally,63 internal openings,138 external openings,56 main fitulars,112 secondary fistulars,and 43 abscesses were found in the operations.Taking operation results as reference,the accuracy for primary tracts and abscesses of MRI was 100%.For 56 cases of patients,the accuracy of routine MR sequences for internal opening,external openingand secondary fistula were 74.6%(47/63),78.2%(108/138)and 73.2%(82/112).As for conventional MR sequences combined with DWI,the accuracy were 88.9%(56/63)for internal opening;89.8%(124/138)for anal fistula;and 86.6%(97/112)for secondary fistulas.In comparison of two kinds of diagnostic methods of perianal fistulas,conventional sequences combined with DWI had better diagnostic values on internal opening,external opening and secondary fistulas than conventional sequences merely,and the differences were statistically significant(P<0.05).Conclusion In the preoperative MRI diagnosis on perianal fistulas,conventional MRI sequence combined with DWI sequence have higher accuracy rate on the detection of internal opening,external opening and secondary fistulas,can provide more detail of anatomical information for clinical preoperative preparation.Part two: The application of DWI-MRI on evaluating complex perianal fistulas activityObjective: To investigate the application value of DWI-MRI and its quantitative parameter(ADC values)for evaluating perianal fistula activity before and after the operations.Methods: 49 patients with histologically proven complicated perianal fistula were selected from the 56 cases in the first part of this study,with all patients underwent conventional 3.0T MRI and axial DWI sequences.Based on the perianal disease activity(PDAI)index,lesions were classified into 2 groups: positive inflammation activity group(19 cases)and negative inflammation activity ones(30 cases).The morphological features of routine and DWI sequences of the lesions were analyzed respectively,and the ADC value of the lesions were measured on the ADC maps.ADCs of both groups were compared using an unpaired t-test,and Receiver Operating Characteristic(ROC)analysis was performed.Ultimately,the correlation relationships between the ADC value and PDAI were analyzed.Results: The mean ADC value(in 10-3/mm2)of the PIA group(0.925±0.148)was significantly lower(p<0.001)than that of the NIA group(1.252±0.170).The area under receiver operating characteristic curve was 0.94,and the cut-off ADC of 1.101 yielded an optimal sensitivity of 80%,a specificity of 94.7%.In the correlation analysis,the ADC value of the lesions correlated negatively with PDAI(r=-0.89,p<0.05)Conclusion: DWI-MRI and ADC value are helpful to evaluate perianal fistula activity with high accuracy,which should be established as one of the routine MR sequences before and after the clinical operations to decrease the recurrence rates.