MR of the small bowel with a biphasic oral contrast agent (polyethylene glycol): technical aspects and findings in patients affected by Crohn's disease

PURPOSE: To report our experience using MR of the small bowel with polyethylene glycol (PEG) solution as an oral contrast agent in a population of adults and children with known Crohn's disease. MATERIALS AND METHODS: 40 patients (29 males; 11 females), 15 adults (age range 24-52 years) and 25 children (age range 5-17 years), with known Crohn's disease, underwent MR of the small bowel using a supeconductive 1.5 T magnet, and polyethylene glycol solution as an oral contrast agent. The fixed amount of contrast agent was 750-1000 ml for adults and 10 ml/kg of body weight for children. The Crohn's Disease Activity Index (CDAI) was available in all patients. Our study protocol included the acquisition of T2-weighted half-Fourier single-shot turbo spin-echo (HASTE) sequences and true fast imaging in the steady-state precession (true-FISP) sequences, followed by the acquisition of "spoiled" 2D gradient echo T1-weighted sequences with fat suppression (FLASH, fast low-angle shot) or alternatively "spoiled" 3D (VIBE, volume interpolated breath-hold examination), acquired 70 seconds after intravenous administration of gadopentetate dimeglumine (Gd-DTPA) (0,1 mmol/kg). A specific MR score was created and calculated for each patient and was compared by means of the Spearman rank with CDAI. RESULTS: In all patients no significant side effects were observed and the MR examination was well tolerated even by paediatric patients. In all cases MR showed a small bowel wall thickening (> 4 mm) in the terminal ileum, with lumen stenosis in 26 patients. In 3 cases pathological segments proximal to the terminal ileum were observed and in another 3 cases caecal involvement was visible. The MR examination was able to show abnormalities of perivisceral fat tissue in 15 patients, mesenteric lymphadenopathy in 1 patient and abdominal abscess in 1 case. The Spearman rank showed a statistically significant correlation between CDAI and the MR score (r = 0.91, P = 0,0001). DISCUSSION: MR using PEG as an oral contrast agent could be considered a test of great interest in the evaluation of the small bowel in patients suspected of having Crohn's disease in that it is easily reproducible, well tolerated even by paediatric patients and it provides useful information about the localisation, extension and activity of inflammatory disease without the use of ionising radiation.