Objective: To weigh the benefits and harms of detecting and pursuing incidental findings on computed tomographic colonography screening in average-risk populations. Data Sources: I searched MEDLINE, EMBASE, ScienceDirect, and the Cochrane Collaboration library from 1996 to present, with all searches limited to English language studies. Study Selection: I developed inclusion and exclusion criteria to examine an average-risk population. Data Extraction: I performed a single data extraction from included studies of fair to good quality for the preparation of evidence tables. I rated the quality of the selected studies using criteria modified from those recommended by the USPSTF for study appraisal. Data Synthesis: Key Question #1: What is the prevalence of all incidental findings detected on CTC? At least one extracolonic finding was detected in 62% of screened patients. 5.9% of patients received additional investigations. One study examined the effects of IV contrast-enhancement. This study reported a lower frequency of patients receiving additional investigation than any of the other studies. Key Question #2: What is the prevalence of specific types of incidental findings? Two studies reported the specific types of findings that were ultimately diagnosed. The most common diagnosed pathologies reported in these studies were nonmalignant tumors (1.5% of screened populations), malignant tumors (0.5% of screened populations) and aortoiliac aneurysms (0.3% of screened populations). Key Question #3: What are the beneficial outcomes of detecting and investigating incidental findings? Three studies reported a total of 114 patients (at least 2.3% of all patients) who received clinical diagnoses. It is uncertain how many of these received treatment, but at least 0.9% of all patients received treatment. The true benefit of pursuing incidental findings is unlikely to include all of the diagnosed and treated pathologies. Key Question #4: What are the harms of detecting and investigating incidental findings? One study reported the number of patients who received additional workup with no reported diagnoses. Underestimated extrapolated values were obtained for two studies. Approximately 3.1% of the patients from these three studies received additional workup with no reported important clinical diagnoses; this value may overestimate the true value. Three studies reported data on invasive procedures that resulted in benign findings. At least 0.5% of patients in these three studies received an invasive procedure that resulted in the diagnosis of a benign finding. All of the patients who receive further investigations with no diagnoses or treatment experience at least some degree of harm. Key Question #5: What are the costs and cost-effectiveness of detection and further investigating incidental findings? The cost of pursuing incidental findings likely falls between 98.56and248. Cost-effectiveness analysis cannot be assessed without a more comprehensive evaluation of the benefits and harms. Conclusion: Incidental findings are found in over half of asymptomatic patients who are screened by CTC. The number of patients who receive additional investigations is much fewer. A small percentage of patients receive clinical diagnoses and treatment. Clinical benefit likely results from some, but not all, of these patients receiving diagnoses and treatment. Likewise, a small percentage of screened subjects received additional workup with no reported diagnoses. All of these received at least some degree of harm. The degree of benefit and harm resulting from each diagnoses, treatment, or additional workup remains unclear. This further complicates the task of weighing the benefits versus the harms. Available data is insufficient to appropriately weigh the overall benefits versus the overall harms.Master of Public Healt
