Comment on "Extracolonic Findings at Screening CT Colonography: Prevalence, Benefits, Challenges, and Opportunities".

Comment on “Extracolonic Findings at Screening CT Colonography: Prevalence, Benefits, Challenges, and Opportunities” We read with great interest the study by Pooler and colleagues [1] about extracolonic findings detectable at screening CT colonography (CTC). This review surely provides valid and reliable support for the management of these findings, often found in daily practice [2]. In this regard we would like to make some comments to the authors and to emphasize the importance of a proper evaluation of the lung bases at screening CTC, looking not only for focal lesions (which are very frequent) but also and above all for diffuse lung disease, especially pulmonary fibrosis. CTC is particularly suitable for this analysis because both supine and prone scans are routinely obtained. The question is, how should we consider the presence of interstitial lung abnormalities (even if low grade and of undetermined nature) in the CT Colonography Imaging Reporting and Data System (C-RADS) assessment extracolonic findings category E? Pooler et al. [3] conducted a study in which the subjects were 7952 adults without symptoms who underwent first-time screening CTC. The authors reported potentially important extracolonic findings (C-RADS category E4) in 202 patients (2.5%); 19 of these patients had pulmonary involvement, but only as nodules or masses without any reference to the presence of diffuse lung disease. In another study in the same study population, Pooler et al. [4] found that 725 patients had C-RADS E3 findings (indeterminate but likely unimportant), of which 19 had unspecified pulmonary involvement defined as “other lung conditions” (excluding patients with pulmonary nodules or masses). Pooler et al. also reported C-RADS category E4 findings in 55 of 660 patients. One of these findings was nonspecific interstitial pneumonia, one was lymphangioleiomyomatosis, and two were pneumonia. In a retrospective evaluation we recently started at our center—ongoing and with only preliminary data—we found 16 patients with interstitial lung abnormalities in a total of 625 patients (2.6%). Several studies [5–7] have shown that asymptomatic interstitial lung abnormalities can be detected in approximately 8% of the general population. Data obtained in lung cancer screening studies show that subclinical interstitial abnormalities are present in approximately 7% of patients (of which 2% have honeycombing) [5]. These alterations, which are always progressive, lead to increased risk of development of symptomatic pathologic conditions in approximately 10 years, with a commensurate increase in mortality. Moreover, after 2–4 years of follow-up, approximately 20–40% of these patients have clinically significant progression of pulmonary fibrosis, sometimes with development of the usual interstitial pneumonia pattern [6, 7] (Fig. 1). How should the radiologist classify these findings? The recent introduction of specific therapies for pulmonary fibrosis [8] requires greater commitment by the radiologist in characterization of interstitial lung abnormalities detectable at screening CTC. We strongly believe that all fibrotic interstitial abnormalities should be classified directly as C-RADS category E4 to direct patients toward the proper diagnostic and therapeutic pathway. Antonio Poerio Francesco Monteduro Maurizio Zompatori Universita degli Studi di Bologna, Azienda Ospedaliera Sant’Orsola-Malpighi, Bologna, Italy a.poerio@alice.it DOI:10.2214/AJR.17. 18719