Enterocutaneous fistulas: a primer for radiologists with emphasis on CT and MRI.

Enterocutaneous fistulas (ECFs) represent abnormal communications between the gastrointestinal tract and the skin. Nowadays, the majority (~80%) of ECFs develops secondary to abdominal surgeries; alternative, less common causes include chronic inflammatory bowel diseases (IBD) such as Crohn's disease, tumours, and radiation enteritis in descending order of frequency. These rare disorders require thorough patient assessment and multidisciplinary management to limit the associated morbidity and mortality. This pictorial review includes an overview of causes, clinical manifestations, complications and management of ECFs. Afterwards, the imaging appearances, differential diagnoses, and therapeutic options of post-surgical, IBD-related, and malignant ECFs are presented with case examples. Most of the emphasis is placed on the current pivotal role of CT and MRI, which comprehensively depict ECFs providing cross-sectional information on the underlying postsurgical, neoplastic, infectious, or inflammatory conditions. Radiographic fistulography remains a valid technique, which rapidly depicts the ECF anatomy and confirms communication with the bowel. The aim of this paper is to increase radiologists' familiarity with ECF imaging, thus allowing an appropriate choice between medical, interventional, or surgical treatment, ultimately resulting in higher likelihood of therapeutic success.

TEACHING POINTS: • Enterocutaneous fistulas may complicate abdominal surgery, sometimes Crohn's disease and tumours. • The high associated morbidity and mortality result from sepsis, malnutrition and metabolic imbalance. • The multidisciplinary management of ECFs requires thorough imaging for correct therapeutic choice. • Radiographic fistulography rapidly depicts fistulas and communicating bowel loops in real-time. • Multidetector CT and MRI provide cross-sectional information on fistulas and underlying diseases.