Use of the star sign to diagnose internal fistulas in pediatric patients with penetrating Crohn disease by MR enterography.

Development of internal fistula due to extramural spread of inflammatory bowel disease is a characteristic feature of penetrating disease in patients with Crohn disease. The "star sign" is a radiological finding of internal fistula that has previously been described in the gastroenterology literature in adult Crohn disease patients undergoing MR enteroclysis. The goal of this paper is to review the clinical and imaging features of penetrating disease in pediatric Crohn disease patients, highlighting the star sign as a useful diagnostic tool for diagnosing internal fistula in children by MR enterography. The recognition of penetrating complications by MR imaging can have important therapeutic and prognostic implications.