Imaging of perianal fistulizing Crohn's disease

Perianal fistula is a complication of Crohn's disease that carries a high morbidity. It is a channel that develops between the lower rectum, anal canal and perianal or perineal skin. The development of perianal fistulas typically connotes a more aggressive disease phenotype and may warrant escalation of treatment to prevent poor outcomes over time. Based on fistula anatomy, debris can form inside these tracts and cause occlusion, which subsequently leads to abscess formation, fever and malaise. The clinical presentation is often with complaints of pain, continuous rectal drainage of fecal matter as well as malodorous discharge. Considering that the presence of fistulas often indicates refractory and aggressive disease, early identification of its presence is important. Some patients may not have the classic symptoms of fistulizing disease at presentation and others may have significant scarring and/or pain from previous fistulizing episodes, which can make an accurate assessment on physical exam alone problematic. As a result, utilizing diagnostic imaging is the best means of identifying the early signs of perianal fistulas or abscess formation in these patients. Several imaging modalities exist which can be used for diagnosis and management. Endoscopic ultrasound and pelvic MRI are considered the most useful in establishing the diagnosis. However, a combination of multiple imaging modalities and/or examination under anesthesia is probably the most ideal. Incomplete characterization of the fistula tract(s) extent or the presence of abscess carries a high morbidity and far-reaching personal expense for the patient - promoting worsening of the disease.