Despite the importance of CD prognosis in determining patient well‐being, most of the studies into the genetic contribution to prognosis have focused on small numbers of susceptibility SNPs in relatively small numbers of patients and have unsurprisingly provided inconsistent results.114, 115, 116 One of the few replicable associations identified was between variants in NOD2 and need for surgery,117 although this was subsequently shown to be entirely driven by the association between NOD2 and ileal disease (which is most commonly treated with surgery). This evidence concerns the gene NOD2 and Cowden disease.