We have found that regions with high rates of chest or abdominal CT scanning
also tend to be regions with high rates of kidney removal.
The advent of CT scanning transformed medicine in the early 1970s, by enabling clinicians to see details of internal organs that can’t be seen in conventional X-rays. While invaluable in determining what wrong with the acutely sick and injured, the widespread use of CT scans has an unintended side effect: the identification of what’s known as incidental tumors, or those that are unrelated to the clinical symptoms that initiate the test. Such coincidental findings have the potential to lead to overdiagnosis and to overtreatment, including unnecessary surgery.
Researchers at The Dartmouth Institute are exploring the geographic variation in CT scanning in the United States and how it relates to nephrectomy or surgical removal of the kidney. We have found that regions with high rates of chest or abdominal CT scanning also tend to be regions with high rates of kidney removal. After ruling out several alternative hypotheses, we concluded that while there has been considerable concern about excessive CT scanning because of radiation-induced cancer, incidental cancer detection and unnecessary surgery is probably the more important risk.
In an analysis of 306 Hospital Referral Regions, Dartmouth Institute researchers are exploring the geographic variation in CT scanning in the United States. The five-year risk of receiving either a chest or abdominal CT varied from 31% in Santa Cruz, CA, to 52% in Sun City, AZ. We also examined the geographic variation of nephrectomy (surgical removal of the kidney) and found that regions with high rates of chest or abdominal CT scanning also tend to be regions with high rates of kidney removal. Scanning an additional 1,000 Medicare beneficiaries was associated with four additional nephrectomies.
This work melds two longstanding lines of Dartmouth research: geographic variation and cancer overdiagnosis. It has long been known that discretionary medical interventions, such as diagnostic testing, vary widely. Cancer overdiagnosis may be less familiar, although it now recognized to be a problem for kidney cancer, as the incidence of the disease has more than doubled over the past 30 years, while mortality has been stable.
H. Gilbert Welch