 Recent work has highlighted the use of magnetisation transfer MT MRI techniques7 in quantifying inflammation and differentiating this from fibrosis. MT generates contrast that is determined by the fraction of large macromolecules and the immobilised phospholipid cell membranes in tissues. Particularly when combined with T2 measurements, MT may be helpful in differentiating and quantifying inflammation by the relative absence of collagen, and differentiating inflamed perianal fistulas that need treatment from other chronic fibrotic and irreversible fistulas that would not be responsive to treatment - better selecting patients for expensive medical or surgical treatment. 