Contrast radiology, computed tomography and ultrasonography in detecting internal fistulas and intra-abdominal abscesses in Crohn's disease: a prospective comparative study

OBJECTIVE: Accurate assessment of intestinal complications of Crohn's disease (CD) is extremely important, both in clinical practice and in trials. The accuracy of radiographic and ultrasonographic diagnosis of internal fistulae and abscesses complicating CD is still debated and requires further investigation. We compared ultrasonography (US) and contrast radiography in detecting intestinal fistulae and abscesses complicating CD. METHODS: A prospective study was carried out on 625 consecutive CD patients who underwent complete evaluation of the intestinal tract by means of colonoscopy and double contrast barium enema, small bowel enteroclysis, and abdominal ultrasound (US). Computed tomography (CT) was also carried out in cases of severe CD with clinical suspicion of septic complications. The accuracy of US, barium radiology, and CT in detecting internal fistulae and abscesses was assessed by comparing results with intraoperative findings in 128 consecutive patients who underwent operation immediately after diagnostic workup. RESULTS: Internal fistulae and intra-abdominal abscesses were identified intraoperatively in 56 (43.7%) and 26 (20.3%) patients, respectively. Diagnostic accuracy of US and x-ray studies in detecting internal fistulae was comparable (85.2% vs 84.8%), with sensitivity of 71.4% for US and 69.6% for x-ray studies, and specificity of 95.8% for both. Combination of radiographic techniques and US significantly improved diagnostic accuracy in detection of internal fistulae. In severe cases of CD with clinical suspicion of septic complications such as abdominal mass or fever, the accuracy of US, barium studies, and CT was 88.5%, 80.3%, and 77%, respectively (p = ns). The presence of abscesses was correctly detected in 90.9% of cases by means of US and in 86.4% by CT (p = ns), although accuracy was higher for CT (91.8%) than for US (86.9%) because of false positive results in US studies. CONCLUSIONS: Despite the fact that barium radiology is widely considered the method of choice in detection of internal fistulae, accuracy is not entirely satisfactory. Comparable accuracy was found for US and CT. The combination of barium and US studies, or the sole use of US in more CD patients with more severe disease, can reliably detect most internal fistulae and abscesses.