Analysis Of The Characteristics Of Perianal Fistula In Crohn’s Disease Based On MRI

Background:The diagnosis of Crohn’s disease is more complicated and requires comprehensive multidisciplinary evaluation.For patients with PFCD involved in surgical treatment,imaging examination is more suitable.MRI has become an important means of studying Crohn’s disease in recent years due to its simplicity and non-invasions.However,there are few descriptions of MRI characteristics of perianal fistulizing Crohn’s disease,and there is a lack of large sample studies.Objective:To analyze the anatomical and inflammatory features of perianal fistulizing Crohn’s disease by MRI,to evaluate the significance of MRI in the evaluation of PFCD,and to compare the reliability of two kinds of MRI scores.Methods:This study is a retrospective study of Jiangsu Provincial Hospital of Traditional Chinese Medicine.Patients with perianal fistulizing Crohn’s disease who underwent rectal MRI from June 2019 to December 2020 were included in the image storage and transmission system of Jiangsu Provincial Hospital of Traditional Chinese Medicine.Record its general information,including gender,age,course of illness,and Montreal classification.At the same time,read MRI images and record relevant parameters,including:the number and location of internal openings,classification of fistulas,gaps,muscles,fistula complexity factors(fistula branches,horseshoe-shaped fistulas,accompanied by abscesses,whether or not rectovaginal fistula),inflammatory indicators(T2 hyperintensity,proctitis exists),and finally calculate the original and modified Van Assche scores based on the MRI information.Results:Among 105 cases of PFCD,75 were males and 30 were females.The course of Crohn’s disease was 20d-16 years,with a median of 2 years.The age of patients with anal fistula was between 12-59 years old,with an average of 28.8.±9.9 years old.The diagnosed age of CD was≥16 years old,17-40 years old and>40 years old accounted for 11.4%,80.0%,and 8.6%respectively.The ileocolonic type accounted for 60%of the lesions,the ileal type alone and the colon alone type accounted for 21%and 20%,respectively,and the upper gastrointestinal type was at least 1.0%.In the disease behavior,the inflammatory type accounted for 71.4%,the stenosis type and the penetrating type accounted for 21.0%and 7.6%,respectively.In the disease behavior,the inflammatory type accounted for 71.4%,the stenosis type and the penetrating type accounted for 21.0%and 7.6%,respectively.A total of 100 cases(95.2%)with a clear internal orifice can be found in MRI,of which 89 cases(84.7%)have a single internal orifice,and 11 cases(10.5%)have multiple internal orifices.Among patients with a clear internal opening,the height of the internal opening was measured by the tooth line,and 56 cases(56%)were above the tooth line;the position of the internal opening was marked by the lithotomy position,and the number of internal openings at the 6 o’clock position was the largest.In 37 cases(37%),the stone cutting position was divided into front side(1,11,12 o’clock),back side(5,6,7 o’clock),lateral(2,3,4 o’clock on the left,8,9,10 o’clock on the right),the distribution statistics of the inner mouth P>0.05.There were 83 cases(79%)of complex anal fistula.According to the parks classification,transsphincteric fistulas were the most,41 cases(39.1%),subcutaneous anal fistulas were the least,only 5 cases(4.8%),and the intersphincteric fistula,suprasphincteric fistula and extrasphincteric fistula were 20 cases(19.0%),18 cases(17.1%),21 cases(20.0%).In terms of the number of fistulas,there were 49 cases(46.7%)without a single branch,32 cases(30.5%)with a single branch,and 24 cases(22.8%)with multiple fistulas.Only 1 case(1.0%)had a fistula passing through the subcutaneous part of the external sphincter,33 cases(31.4%)in the superficial part of the external sphincter,13 cases(12.4%)in the deep part of the external sphincter,and 31 cases(29.5%)in the levator ani muscle.Fistulas often pass through multiple gaps.The sphincter gap is the most common,accounting for 52.4%of the total.The perianal gap is the least,only 10.5%.The ischiorectal gap and the supralevator ani gap account for 21.0%and 21.9%,respectively.The distance from the highest point of the supervisor to the anal edge is 4.67±1.70cm.The second series of correlation analysis found that the supralevator ani muscle fistula was moderately correlated with the highest point of the supervisor exceeding 5cm(r=0.527,p<0.001),and the fistula via the ischiorectal fossa had a weak correlation with the highest point of the supervisor exceeding 5cm(r=0.332,p=0.024).51.4%of the patients had a clear abscess,and 25.7%of the patients showed a horseshoe-shaped fistula.Recto-vaginal fistula was relatively rare,only 4 cases(3.8%).In 77 patients,the fistula showed obvious hyperintensity in the T2 sequence(73.3%),and 73 cases(69.5%)had thickened intestinal wall and hyperintensity in the intestinal wall.The number of fistulas in the original and modified versions of van Assche,fistula location,fistula extension,T2WI hyperintensity,rectal wall invasion,bronchial/inflammatory mass,and rectal-vaginal fistula are several items in the evaluation of the intra-group correlation coefficient of PFCD(95%confidence interval)are 0.99(0.989,0.995),0.72(0.039,0.922),0.67(0.499,0.781),0.062(0.033,0.233),0.893(0.846,0.926),0.856(0.795,0.9),0.854(0.792,0.898),a total score of 0.857(0.108,0.955),which proves that the two scores have high reproducibility for evaluating PFCD,and the P value is less than 0.001,which proves that the two MRI scores have a high degree of evaluation for PFCD consistency.Conclusion:In this study,Perianal fistulizing Crohn’s disease was more common in young and middle-aged men,and the fistula was more complex,mainly manifested as multiple branches,multiple internal orifices,multiple abscesses,high internal orifices,and high frequency rectal inflammation.For young patients presenting only with complex or recurrent anal fistula,it is necessary to be vigilant against the presence of Crohn’s disease and to carry out endoscopic,pathological and laboratory indicators screening as far as possible to prevent delayed diagnosis.MRI is of great significance in evaluating the structure of PFCD and the existence of inflammation.It can guide treatment to a certain extent and evaluate the therapeutic effect at the same time,so it should be the first choice for imaging examination of PFCD.The original and modified Van Assche scores are highly consistent in the evaluation of Crohn’s disease fistulas,and can be used to evaluate the complexity of PFCDs,but the modified version of the scoring rules is more detailed.