Role of digital infrared thermal imaging in surgical management of fistula-in-ano

Anal fistulas represent an inflammatory condition with a connection formed between the anal canal and the perianal skin. Surgery aims to eradicate the fistula while preserving sphincter function. However, inadequate removal of fistula tracts often results in recurrence, and excessive division of the anal sphincter complex can result in fecal incontinence. Therefore, comprehensive preoperative evaluation of the fistula tract is crucial and contributes considerably to outcomes. MRI has emerged as a key method in patients with perianal fistula, but is expensive, uses intravenous contrast agent, and experience is needed to interpret images. Endoanal ultrasound (EUS) is cheaper and more practical than MRI, but is highly operator dependent and its role in suprasphincteric and complex fistulas is controversial. This study aimed to assess the usefulness of digital infrared thermal imaging (DITI) for evaluating of fistula-in-ano. DITI monitors infrared radiation emanated by a surface, in this case the perianal skin. The scientific rationale is based on the inflammatory state caused by perianal fistulization. Because one of the pathological findings of inflammation is increased local temperature due to altered blood flow, we hypothesized that by using a contrast agent colder than the human body, the perianal fistula tract could be visualized by DITI cameras. A protocol and simple diagnostic algorithm for evaluation of perianal fistulas are presented.