A systematic review and meta-analysis of the diagnostic test accuracy of diffusion weighted imaging and apparent diffusion coefficient in differentiating active from inactive perianal fistula

Abstract

Introduction

This systematic review and meta-analysis evaluated the diagnostic accuracy of MRI-based apparent diffusion coefficient (ADC) and diffusion-weighted imaging (DWI) for differentiating active from inactive perianal fistulas.

Methods

The protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42024596604). The review included five databases (MEDLINE, Cochrane Library, PubMed, Science Direct, and Google Scholar). Meta-analyses were performed on studies reporting ADC values and other sequences using STATA software with the “Midas” command.

Results

Of 21 studies included in the review, 12 were meta-analyzed, encompassing 1007 patients (77.5 % male) with 1092 fistulas and 321 abscesses. Six studies reported ADC values for active vs. inactive fistulas, with a pooled sensitivity of 83 % (95%CI 68–92), specificity of 75 % (95%CI 60–85), and AUC of 0.85 (95%CI 0.81–0.87). Pooled ADC cut-offs ranged from 1.105 to 1.109 × 10⁻³ mm²/s. The T2WI + DWI sequence demonstrated the highest diagnostic accuracy, with a pooled sensitivity of 99 % (95%CI 90–100), specificity of 97 % (95%CI 79–100), and an AUC of 1.

Conclusion

ADC alone is inadequate for reliably distinguishing active from inactive fistulas. T2WI combined with DWI offers superior diagnostic performance, surpassing contrast-enhanced T1WI, and is promising for non-invasive evaluation of perianal fistulas. However, several limitations, such as moderate to high risk of bias and heterogeneity, may bias this conclusion.

Implications for practice

T2WI + DWI could become the standard for assessing perianal fistulas, avoiding contrast agents, and benefiting patients contraindicated for Gadolinium-based contrast media. Variability and potential bias across studies warrant further research.