Detection of potentially relevant extracolonic and colorectal findings at CT colonography in a low-risk symptomatic patient population

CT colonography (CTC) is a widely accepted examination tool for detection of colorectal lesions but evidence of the proportions of relevant extracolonic findings (ECF) in a large symptomatic but still relatively low-risk cohort is lacking, as well as their relationship to symptoms, age, and sex.

All patients (n = 3208) with colorectal symptoms, imaged between January 2007 and September 2016 with first-time CTC, were retrospectively selected. The majority (96.7%) was examined with low-dose unenhanced protocol. The most relevant ECF and colorectal lesions (ae6 mm) were prospectively assessed according to C-RADS classifications. Follow-up was elaborated based on the electronic record review. Chi-square test was utilized for evaluating the associations between relevant findings and symptoms, age, and sex.

A total of 270 (8.4%) patients were classified as C-RADS E3, 63 (2.0%) patients as C-RADS E4, and 437 (13.6%) patients were assessed with colorectal lesions (C-RADS C2-4). At follow-up, two thirds of ECF turned out to be a malignancy or relevant disease that required further medical attention. The proportion of ECF was not related to specific colorectal symptoms. Patients aged ae65 years and men had significantly higher proportions of ECF than younger patients (C-RADS E3 p = 0.005; C-RADS E4 p <0.001) and women (C-RADS E3 p = 0.013; C-RADS E4 p = 0.009), respectively.

Proportions of relevant ECF and colorectal findings are relatively low in symptomatic low-risk patients. By use of CTC as a singular examination, especially in elderly patients, most colonoscopies can be avoided with the benefit of diagnosing relevant ECF without introducing substantial over-diagnosis.