Rectal water injection multi-modal MRI high resolution scan can be used for preoperative diagnosis of patients with anal fistula

ZHAO Mengwen; TANG Yongxiang; GE Jun; LI Shijian; ZHANG Ran; HONG Dandan; CEHNG Hui; YUAN Weimin; ZHANG Yifan

doi:10.12122/j.issn.1674-4500.2024.11.07

Abstract：Objective To preliminarily investigate the application value of multi-modal MRI high-resolution scanning with rectal water instillation in the diagnosis of anal fistula.Methods Patients who were diagnosed with anal fistula in our hospital from October 2022 to January 2024 were selected for MR examinations.More specifically,following routine MRI sequence scanning,these patients received the same sequence scanning and dynamic contrast-enhanced MRI(DCE-MRI)examinations after rectal water instillation.In this foundation,this research further compares the clarity of fistulas as well as the relationship between fistulas and adjacent sphincters in each conventional sequence,thereby identifying the optimal sequence.Furthermore,this research compares the changes in fistula length,the maximum diameter of fistulas,the internal orifice diameter of fistulas and the detection rate of fistula before and after rectal water instillation in the optimal sequence.Results A total of 67 fistulas were observed in 41 patients with anal fistula confirmed by surgery and pathology.Specifically,T1WI,T2WI,three-dimensional spin echo with short time inversion recovery(3D-STIR-TSE)sequences before rectal water instillation as well as DCE-MRI sequence after rectal water instillation exhibited significant differences in the clarity of fistulas and the relationship between fistulas and adjacent sphincters(P<0.05),among which 3D-STIR-TSE sequence performed best.Further analysis of 3D-STIR-TSE sequence demonstrated that there were statistical differences in the length,maximum diameter,and internal orifice diameter of fistulas before and after rectal water instillation(P<0.05).Moreover,regarding the contrast of the clarity of fistulas before and after rectal water instillation,the detection rate of fistulas before rectal water instillation was 89.55%,whereas that after rectal water instillation increased to 98.51%.The difference between them was statistically significant(P=0.04).Conclusion 3D-STIR-TSE sequence achieves the optimal performance in the diagnosis and examination of anal fistula by multi-modal MRI.The easy-operated multi-modal MRI examination with rectal water instillation,being a pivotal supplement to routine MRI examinations,is capable of improving the diagnostic ability for fistulas.