Color ultrasound and MRI anal fistula is not more accurate, both have their advantages and disadvantages, for different case characteristics of different means of detection, the need for comprehensive judgment to be able to make a clear diagnosis. 1. color ultrasound: color ultrasound can clarify the specific location of the fistula orifice, for the location of superficial fistula can be clear under the ultrasound examination of the location of the anal fistula, the scope of the position of the relationship with the surrounding sphincter, the accuracy rate is high, for the differential diagnosis of certain clinical significance, but for the deeper part of the fistula orifice of the shadow is easily affected, resulting in the development of the shadow is not clear enough. 2. Nuclear magnetic resonance: for the location of the deep fistula has special diagnostic significance, can clearly show the location of the fistula, the scope and the relationship with the sphincter, for some special cases it is difficult to find the mouth of the fistula, can effectively avoid omissions, can be given to the correct positioning of the mouth. For the definitive diagnosis of anal fistula, we need to carry out a comprehensive judgment, combined with various imaging tests, should not look at a single, need to be comprehensive examination, the patient also need to follow the doctor’s instructions to actively cooperate with the doctor to improve the relevant examination.