Virtual colonoscopy - CT colonography our experiences

Abstract

Introduction: Virtual colonoscopy (VC) produces two-dimensional images and a detailed 3-D model of the abdomen and pelvis to view the bowel in a way that simulates travelling through the colon as in a conventional colonoscopy. Furthermore, it has been validated as a colorectal cancer test that provides an additional minimally invasive screening option which is likely to be preferred by some patients. Aim: The aim of this paper is to present our experience from technical and clinical aspect, based on the VC examinations performed at our clinics. Material and method: In all patients a thin tube is inserted into the rectum so that air to be pumped to inflate the colon for better viewing. No sedation is administered. Endoluminal lesions are categorized according to size: A lesion is defined as a mass if its diameter at VC is 20 mm or larger, as a large polyp if its diameter is 10 mm or larger but smaller than 20 mm, and as a medium polyp if its diameter is 6 –9 mm. diminutive lesions are polyps less than 5 mm. Results: VC is usually regarded as “not painful” compared with colonoscopy. Discomfort from air filling of the colon is the major complaint about VC. In VC polyps smaller than between 2 and 10 millimetres in diameter may not show up. Furthermore, it is not recommended for patients with active Crohn's disease, ulcerative colitis, inflammatory bowel disease or diverticulitis, because of increased risk of perforating the colon. Discussion: The American Cancer Society (ACS) recommends that women and men undergo screening for colon cancer or polyps beginning at age 50. Results of a prospective study, held from 2004 to 2008 at two centers shows that the overall detection rate of unsuspected cancer has been approximately one per 200 asymptomatic adults undergoing routine screening VC, including about one invasive CRC per 500 cases and one extracolonic cancer per 300 cases. Detection and treatment at an early presymptomatic stage may have contributed to the favorable outcome. The results of large studies have demonstrated that the diagnostic performance ofVC approaches that of optical colonoscopy for detection of colorectal polyps that are 1 cm or larger. Conclusions: VC is considered less painful and less difficult overall than colonoscopy and is the preferred examination for the patients. Studies suggest that VC is an alternative or complement to current methods in clinical practice.