| Anal fistula is a chronic inflammatory abnormal epithelialized channel between the anorectal and perianal skin.With changes in people’s daily diet and lifestyle habits,the incidence of anal fistula is increasing year by year.Surgery is the main method for radical treatment of anal fistula.Perform radiological examination to accurately determine the location of the internal opening of anal fistula,the direction of fistula and its relationship to the anal sphincter before surgery can reduce postoperative recurrence.Auxiliary examinations include three-dimensional endoanal ultrasound(3D-EAUS),multi-slice computed tomography(MSCT)or magnetic resonance imaging(MRI).At present,the comparison of different radiological techniques in the diagnosis of anal fistula was rarely reported.MRI’s high resolution and good spatial display of soft tissues can show the anatomical relationship between the lesion and the surrounding tissues more accurately.The choice of sequences to clearly show more internal orifices and fistulas has also been discussed by imaging physicians,and the current conventional scanning sequences for MRI of anal fistulas include T1-weighted imaging(T1WI),T2-weighted imaging(T2WI),fat-suppression T2-weighted imaging(FST2WI),contrast-enhanced fat suppression Tl-weighted imaging(CE-FST1WI),and diffusion weighted imaging(DWI),among which CE-FST1WI is relatively clearer to show the internal opening of anal fistula and the direction of fistula.However,the application of CE-FST1WI requires the injection of contrast agent,which has some potential risks and much more expensive.Therefore,seeking a safe,noninvasive and effective MRI sequence for anal fistula examination is necessary.[Objective]A systematic evaluation and meta-analysis of three different imaging methods(3D-EAUS,MSCT,and MRI)in the diagnosis of anal fistula was performed to provide reliable evidence for recommending better imaging methods.In the meanwhile,the four MRI sequences of T1WI+FST2WI,DWI,T1WI+FST2WI combined with DWI and CE-FST1WI were analyzed and recorded for the diagnosis and staging of anal fistula,and the advantages and disadvantages of the four sequences for the display of anal fistula structures were compared to provide a theoretical basis for the clinical recommendation of better MRI examination sequences.[Methods]Part Ⅰ:Meta-analysis of diagnostic tests was performed using RevMan 5.4.1 software.3D-EAUS and MRI were based on Parks typing,while MSCT was based on high and low complex fistulas.The specificity(SPE),sensitivity(SEN),negative predictive value(NPV),positive predictive value(PPV),negative likelihood ratio(LR-),positive likelihood ratio(LR+),and summary subject operating characteristic curve(sROC)of the three different diagnostic imaging methods(3D-EAUS,MRI,and MSCT)were compared.Part Ⅱ:Clinical and MRI data of 46 patients with anal fistula were collected and collated,and the four sequences of T1WI+FST2WI combined with DWI,T1WI+FST2WI,DWI,and CE-FST1WI were counted to show the number of internal openings,number of main fistulas,presence of branch fistulas,number of branch fistulas,and presence of pus cavity,using surgical pathology results as the gold standard.Correlation analysis was performed using R.4.0.2.[Results]Part Ⅰ:A total of 1829 documents were searched,and those whose study subjects did not meet the inclusion criteria were deleted,and a total of 27 documents were finally included in the systematic evaluation and meta-analysis,among which:3D-EAUS documents 10,MSCT documents 3,MRI documents 14.Using the surgical findings as the gold standard,the sROC curves of 3D-EAUS,MSCT and MRI showed that most points fell on the curve or were located in the upper left corner of the curve,suggesting that they all showed diagnostic effects.The specificity of 3D-EAUS for all types of anal fistula was good(SPE>0.9)and the probability of true positives was high(LR+>10),but it was only sensitive to detect transanal sphincter fistula(SEN>0.9),and the sensitivity of other types was poor(SEN<0.9).The diagnostic specificity and probability of true-positive diagnosis of high-grade complex fistulas,low-grade complex fistulas and the number of internal openings were good with MSCT(SPE>0.9,LR+>10),but the sensitivity was poor(SEN<0.9);MRI has good sensitivity and specificity for all types of anal fistulas(SPE,SPE>0.9),both in plain and combined enhancement,and has a high probability of diagnosing true positives and true negatives(LR+>10,LR-<0.1).In addition,MRI is also more sensitive in diagnosing the number of internal orifices and fistulae(SEN>0.9).In general,MRI is a better choice for identifying the type of fistula and the number of internal openings and fistulas.Part Ⅱ:Using the surgical situation as the gold standard.The results showed that T1WI+FST2WI+DWI and CE-FSTiWI could show the internal orifice of the fistula better,with a display rate of 91.23%and 96.49%,respectively,which were not statistically different from the surgical results(P=0.07364,P=0.4795),while T1WI+FST2WI and DWI showed the internal orifice poorly,with the rates of 82.46%and 68.42%,respectively,which were statistically different from the surgical results(P=0.00443,P=0.00006).On the display of the main fistula,T1WI+FST2WI+DWI,CE-FST1WI,and T1WI+FST2WI could be well displayed,and the rates were 96.55%,98.28%,and 94.83%,respectively,which were not significantly different from the surgical results(P=0.47 95,P=1,P=0.4795),but DWI showed poorly for the main fistula(87.93%,P=0.02334);for the branch fistula,the display rates of T1WI+FST2WI+DWI,T1WI+FST2WI,DWI,and CE-FST1WI were 96.00%,96.00%,92.00%,and 96.00%,respectively,with no statistically significant differences from the surgical results(P=1,P=1,P=0.4795,P=1).[Conclusion].1.MRI can be used as a better imaging option for the diagnosis of anal fistula.2.The T1WI+FST2WI+DWI and CE-FST1WI sequences can show the internal orifice,main fistula and branch fistula well,and there is no superiority between them. |
