Ultrasound, CT and colonoscopy of colonic cancer

Barium enema and colonoscopy are commonly used for the investigation of suspected colonic cancer. These techniques are relatively invasive and both the investigation and the preceding bowel preparation are demanding, particularly in the elderly. A prospective, blinded trial was conducted to compare ultrasound (US) and CT with colonoscopy. CT and colonoscopy were performed on 50 patients with symptoms suggesting colonic cancer. Both radiological investigations were performed prior to the bowel preparation for colonoscopy. US was performed without any preparation and oral contrast medium was the only preparation used for CT. Colonoscopy detected six cancers, all of which were diagnosed by both US and CT. In addition, US and CT diagnosed a further cancer not seen on colonoscopy due to an incomplete study. US had a sensitivity and specificity of 100% and CT a sensitivity of 100% and a specificity of 84%. US and CT were poor at diagnosing polyps. If the detection of polyps greater than 2 cm is included then US sensitivity falls to 67% and CT sensitivity falls to 89% and specificity rises to 88%. In conclusion, both US and CT are possible alternatives to colonoscopy in the investigation of symptomatic patients with suspected colonic cancer. The use of these techniques could markedly reduce the need for colonoscopy in this patient population with attendant cost savings. Non-invasive imaging has particular advantages in the elderly who cope poorly with both the bowel preparation and the procedure.