Dynamic contrast-enhanced MRI in determining disease activity in perianal fistulizing Crohn disease: a pilot study.

OBJECTIVE

The objective of our study was to perform a semiquantitative analysis of dynamic contrast-enhanced MRI for the evaluation of disease activity and therapeutic response in patients with perianal fistulizing Crohn disease.

SUBJECTS AND METHODS

Sixteen consecutively registered patients with perianal Crohn disease underwent pelvic MRI. A dynamic contrast-enhanced sequence was performed at 3 T (temporal resolution, 4.2 seconds) during i.v. contrast injection. Maximum enhancement, initial slope of increase, volume transfer constant (K(trans)), and the extravascular space fractional volume (x028B;(e)) were calculated in a region of interest drawn around the fistula. Perianal disease activity index, C-reactive protein concentration, and an MRI-based activity score were calculated as reference standards. Six patients underwent a second MRI examination 6 weeks after starting treatment with anti-tumor necrosis factor α (anti-TNF-α).

RESULTS

Perianal disease activity index moderately correlated with maximum enhancement (r = 0.67, p = 0.005), initial slope of increase (r = 0.58, p = 0.018), and volume of enhancing pixels (r = 0.79, p < 0.001) but not with K(trans) or x028B;(e). Volume of enhancing pixels also correlated with C-reactive protein concentration and the MRI-based score (r = 0.52, p = 0.041; r = 0.79, p < 0.001). The K(trans) values had decreased significantly 6 weeks after the start of anti-TNF-α therapy.

CONCLUSION

Maximum enhancement and initial slope of increase correlate with disease activity in perianal Crohn disease. K(trans) may be an indicator of the effect of therapy on patients starting anti-TNF-α treatment.