The review addressed a clear question with reproducible inclusion criteria. Several relevant sources were searched, but it appeared that unpublished studies were not specifically sought. Diagnostic filters did not appear to have been used in the search strategy, which ensured studies were not missed on this basis. Data extraction was conducted in duplicate, but it was unclear whether similar methods were used to reduce error and bias during study selection or the quality assessment. Study quality was assessed using appropriate criteria, and results were published in full. Data were analysed in a per fistula basis, rather than per patient basis, which may impact on the overall estimates of test accuracy.
The pooled estimates of sensitivity and specificity were derived from analyses that did not maintain the relationship between these measures, and the heterogeneity observed was not investigated. The included studies were published between 1999 and 2004, and used MRI with Tesla strength of 1.0 or below; this is much lower than is commonly used in current clinical practice. There have also been rapid advances in other imaging technology since these studies, including ultrasound, so the results may not be generalisable to current practice.