CT features of Crohn's disease

Clinical History

A 14 year old boy came with 3 years history of weight loss and recurrent abdominal pain

Imaging Findings

A 14 year old boy came with 3 years history of weight loss and recurrent abdominal pain. Barium meal follow through showed multiple strictures,transverse and longitudinal ulceration giving rise to cobblestone appearance. Contrast enhanced abdominal CT scan (CECT) was performed which showed segmental areas of gross thickening of the wall of small bowel loops with luminal narrowing, mesenteric hypervascularity giving rise to the “comb sign” and mesenteric lymphadenopathy. The thickened wall was homogenous in attenuation indicating the chronicity of the disease. Enteroscopic guided biopsy confirmed the diagnosis of Crohn’s.

Discussion

Crohn’s disease is a chronic granulomatous disease which may affect any part of the gastrointestinal tract from oesophagus to anus. Small intestine is the commonest site of involvement. Radiographic imaging studies have a major role in the evaluation of patients with Crohn’s disease, especially with small bowel involvement. They may be performed not only to confirm Crohn’s disease but also to assess the extent and severity of disease, rule out complications, and monitor the response to therapy.   The ability to depict fine mucosal detail has made the double contrast barium study an excellent technique for the diagnosis even in the early stages of the disease. The earliest small bowel change noted is a diffuse granular mucosal pattern. As the disease progresses, there is characteristic irregular thickening and distortion of the valvulae conniventes. Transverse and longitudinal ulceration gives rise to a cobblestone appearance. Continued inflammation and fibrosis results in a narrowed segment of small bowel giving rise to the string sign. Other features noted on barium studies are separation of small bowel loops, strictures and fistulae.   CT yields accurate information regarding the extent of inflamed segment of the bowel, and it can detect potential complications. In one study CT demonstrated unsuspected abnormalities that altered medical or surgical management in 28% of cases. The most common CT finding in Crohn’s disease is discontinuous, asymmetric bowel wall thickening ranging from 1 to 2 cm. The presence of mural stratification (double-halo or target sign) in thickened wall on CT may indicate an acute phase of disease. In chronic disease the thickened wall becomes homogenous in attenuation. Mesenteric hypervascularity gives rise to the classic “comb” sign. Other features that are seen on CT are fibro fatty proliferation within the mesentery, mesenteric lymphadenopathy and abscesses. Fistula and sinus tracks are hallmarks of Crohn’s disease and CT overcomes the limitation of Barium study by demonstrating their full extent. MRI has also been reported to be useful for demonstrating the intestinal and extra intestinal changes of Crohn’s disease. CT enteroclysis and MR enteroclysis are the emerging techniques for evaluation of the small bowel in patients with Crohn’s disease.

Differential Diagnosis List

Final Diagnosis

Crohn's Disease

URL:	https://www.eurorad.org/case/4581
DOI:	10.1594/EURORAD/CASE.4581
ISSN:	1563-4086