Objective
To analyze the incidence and outcomes of unsuspected indeterminate but likely unimportant extracolonic findings (C-RADS category E3) at screening CT colonography (CTC).
Methods
Over 99 months (April 2004 through June 2012), 7952 consecutive asymptomatic adults (3675 men and 4277 women; mean [±SD] age 56.7 ± 7.3 years) underwent first-time screening CTC. Findings prospectively categorized as C-RADS E3 (indeterminate but unlikely important) were retrospectively reviewed, including follow-up (range, 2–10 years) and ultimate clinical outcome.
Results
Unsuspected C-RADS category E3 extracolonic findings were detected in 9.1% (725/7,952) of asymptomatic adults; 25 patients had multiple findings for a total of 751 E3 findings. Commonly involved organ systems included gynecologic (24.4%, 183/751), genitourinary (20.9%, 157/751), lung (20.6%, 155/751), and gastrointestinal (16.1%, 121/751). Consideration for further imaging, if clinically warranted, was suggested in 83.8% (608/725). 65 patients were lost to follow-up. Conditions requiring treatment or surveillance were ultimately diagnosed in 8.3% (55/660), including 8 malignant neoplasms. In the remaining 605 patients, 25 (4.1%) underwent invasive biopsy or surgery to prove benignity (including 18 complex adnexal masses), and 278 (46.0%) received additional imaging follow-up.
Conclusions
Indeterminate but likely unimportant extracolonic findings (C-RADS category E3) occur in less than 10% of asymptomatic adults at screening CTC. Over 90% of these findings ultimately prove to be clinically insignificant, with fewer than 5% requiring an invasive procedure to prove benign disease, the majority of which (>70%) were complex adnexal lesions in women.