The objective of this study was to evaluate normal ileocecal valve (ICV) attenuation and composition on CT colonography (CTC). Two hundred twelve patients who underwent CTC at the authors institution were retrospectively identified. Two independent readers recorded three region-of-interest (ROI) measurements, which were used to determine mean ICV density. ICV attenuation measurements were compared with age and abdominal body fat using Pearson correlation. A subjective classification system was applied to characterize the relative fat and soft tissue density of the ICV Mean ICV density was -26.3 ± 14 HU (range -60.1 to 18.3 HU). There was no correlation between the fat content of the ICVand age (r = 0.06) or body fat (r = —0.47). The majority of valves (83.5%) were classified as heterogeneously low density or hctcro-geneously high density, whereas a small fraction of valves (6.1%) were categorized as homogeneously low density. The results of this study suggest that ICVs have a varying range of densities, and this feature alone cannot be used to distinguish the ICV from a polyp or neoplastic lesion on CTC.
CT colonography (CTC), also referred to as virtual colonoscopy (VC), is a rapidly evolving technique that holds promise as a new method of screening for colorectal cancer. However, there is a wide degree of variability in its reported specificity and performance as a screening test.1 Much of the current research is aimed at improving current VC techniques and protocols as well as reducing the number of false-positive detections.
The ileocecal valve (ICV) is a well-recognized source of false-positive results, as it can mimic the appearance of a polyp or mass. Ordinarily, this problem is avoided by recognition of the normal location and the well-characterized subtypes of the ICV. However, when the typical low-density appearance of the ICV is lacking, or if the valve appears heterogeneous, this may raise concern for a mass in or on the surface of the ICV.
Although the three-dimensional structural appearance of the ICV has been well described, there is little information in the literature regarding the two-dimensional CT imaging characteristics of the normal ICV. A recent paper by Summers et al found that the majority of ICVs seen on CTC had a relatively low internal attenuation, consistent with a "fatty valve." The purpose of this study was to assess the range of normal CT density (used synonymously with attenuation) and heterogeneity of the normal ICV.
