9-year-old boy, with severe bloody diarrhoea and weight loss, affected by UC as confirmed at endoscopy and histology. Three consecutive MRI studies were performed within a period of 14 months from the initial diagnosis, showing caudocranial progression of the colonic disease in spite of the pharmacological therapy. No oral contrast was administered due to low patient compliance. Starting with a prevalent severe involvement of the rectum and sigmoid colon, observed in the first examination, the disease progressed to a severe involvement of the left colon in the second examination and the transverse colon, in the third one. The patient was finally treated with total proctocolectomy and ileo-anal pouch. For a direct comparison, the axial images of the three different examinations are shown consequentially, as well as the coronal views. The first examination includes (a, b and c), the second, performed 10 months after the first one, includes (d, e and f) and the third examination, performed 3 months after the previous (g, h, i and j). Axial T2-weighted half-Fourier single-shot turbo spin-echo (a), axial T1- weighted gadolinium-enhanced images (b) and coronal T2-weighted half-Fourier single-shot turbo spin-echo (c) of the first examination show diffuse wall thickening of the sigmoid colon and extensive Gd-enhancement, suggesting severe inflammation. Notice that the external wall profile is very regular even in very active disease, due to the prevalent inflammation of the inner wall layers (a white arrow). Axial images of the second examination (d and e) show only minimal reduction of wall thickness in the sigmoid colon, severe wall inflammation being still evident. Notice the minimal amount of perivisceral free fluid (white arrow head), suggesting acute disease. On the coronal image (f) a continuous inflammatory involvement from the proximal sigmoid colon up to the splenic flexure (f white arrow) is observed, with loss of the colonic haustra and tubular aspect of the bowel (f black arrow), due to severe wall oedema. In the third and last examination (g, h, i and j) there is a further reduction of wall thickness and a recovery of the austral folds (i white arrow head) in the left colon, due to reduced wall inflammation, as also confirmed at endoscopy. Unfortunately, the disease progressed and worsened in the transverse colon (j). Due to persistence of severe symptoms the patient underwent total colectomy.

Active ulcerative “pancolitis with back-wash ileitis” in a 10-year-old male with clinical and endoscopic signs of active UC. This patient assumed a biphasic oral contrast agent. a The coronal True FISP image shows a mild diffuse thickening of the terminal ileum (white arrow), as well as of the right colon. b T1 VIBE post-contrast fat-saturated coronal MRI image of the same patient shows diffuse wall enhancement of terminal ileum, ileocecal valve and right colon, findings consistent with active colitis and backwash ileitis (white arrow head)