Prognostic value of magnetic resonance imaging in the management of fistula-in-ano

PURPOSE: Magnetic resonance imaging of fistula-in-ano has been shown to predict surgical anatomy accurately and identify complex features. In addition, fistula complexity has been correlated with poor outcome after surgical intervention. We investigated whether preoperative magnetic resonance imaging could predict clinical outcome after surgery for fistulous disease better than clinical examination under anesthetic, METHODS: Seventy patients with clinically suspected fistula-in-ano underwent preoperative dynamic contrast-enhanced magnetic resonance imaging before surgical exploration. Outcome was assessed at a minimum of one year after surgical exploration and correlated in a blinded fashion with the surgical and magnetic resonance grading of the security of the fistulous disease. RESULTS: Of 70 patients, 12 were trot operated on and 6 were lost to follow-up, making 52 patients eligible for analysis. Assessment by dynamic contrast-enhanced magnetic resonance imaging more accurately predicted outcome than the findings at initial surgical exploration. Dynamic contrast-enhanced magnetic resonance imaging had a sensitivity of 81 percent, specificity of 73 percent, and positive predictive value of 75 percent; surgery had a sensitivity of 77 percent, specificity of 46 percent, and positive predictive value of 59 percent. Surgical assessment of apparent disease severity bore no relation to final outcome. Dynamic contrast-enhanced magnetic resonance imaging could accurately predict whether patients were likely to have a satisfactory or unsatisfactory outcome after surgery. CONCLUSION: Dynamic contrast-enhanced magnetic resonance imaging better predicts clinical outcome of patients with fistula-in-ano than initial surgical exploration.