Crohn's disease: value of diagnostic imaging in the evaluation of anastomotic recurrence.

In patients who had previously undergone ileocolic resection due to Crohn's disease (CD) complications, anastomotic recurrence is a frequent event, which may lead to further surgical interventions. Optical colonoscopy with retrograde ileoscopy is currently the reference standard technique to confirm the clinical suspicion of anastomotic recurrence; however, the ileal side of ileocolic antzstomoses may not be assessed due to technical complexities in approximately 1/3 of cases. Moreover, endoscopy allows for an investigation limited to the mucosal surface without demonstrating trans-mural involvement and/or penetrating complications (i.e. fistulas and abscesses). Imaging plays an important role in the assessment of both ileocolic and entero-enteric anastomoses in patients with CD. Conventional radiological methods (i.e. small bowel enteroclysis and small bowel follow through) can effectively depict the presence of aphthous ulcers and other mild and subtle mucosal abnormalities, but they are not precise for the diagnosis of transmural and extramural disease. CT - and MR- enterography accurately demonstrate both the extent of bowel wall involvement and the presence of penetrating complications. The main cross sectional imaging findings observed in CD (including anastomotic recurrence) are small bowel wall thickening with bilaminar or trilaminar stratification, hyperdensity and oedema of the mesenteric fat, engorged mesenteric vasa recta ("comb sign"), sub-mucosal fibre-fatty infiltration and mesenteric adenopathy. Ultrasonography performed after distension of small bowel loops with anechoic contrast agents (Small Intestine Contrast Ultrasonography - SICUS -) is a non-invasive imaging technique which can detect early inflammatory alterations of the anastomosis. On the other hand ultrasonography is an operator-dependent technique and it lacks of a large anatomic field of view.