Here’s the case: A 34-year-old female presents with right flank pain radiating to her right lower quadrant with associated nausea, vomiting, and dysuria. She reports similar symptoms at least four times in the preceding 2-years, always attributed to her kidney stones. Your physical exam reveals no reproducible RLQ tenderness, flank pain, or suprapubic pain. Her pelvic exam is unremarkable. With her urinalysis pending, you quickly review your newly acquired electronic health records and note seven evaluations in your ED over the last 2.5 years with seven CT-scans performed, each time revealing non-obstructive nephrolithiasis. Each time she was discharged home with narcotic and NSAID analgesia. She has never required a urological procedure for her kidney stones. You contemplate your next move…
With over 60 million scans per year in the United States, CT has undoubtedly revolutionized diagnostic radiology with three-dimensional images in tissue plains not accessible by plain film radiography. In 2007 two Columbia University Radiologists published a controversial narrative review suggesting a reappraisal of CT in light of evidence implicating CT as a significant and increasing source of radiation exposure.
The dose of radiation from a CT is substantially more than a plain film exposure. An abdominal CT, for example, has at least 50-fold higher organ dose exposure than an abdominal X-ray. In kidney stone patients, CT scans have three-fold higher radiation exposures than a three-film IVP. Based upon Japanese nuclear bomb survivors, a 20-year old has a 1:1000 lifetime cancer risk from a single abdominal CT. In 2002, CT examinations accounted for 70% of all medical radiation exposure – and this percentage is increasing. The factors impacting radiation dose include the number of CT scans, patient size, scanning range and overlap, tube voltage, scanning time, and specific scanner used. For emergency medicine, the only risk factor within our control is the number of scans ordered.
While CT scanning may significantly impact first-time nephrolithiasis patients, many kidney stone patients will have more than one scan performed over the course of their lifetimes. One North Carolina chart review of 306 potential kidney stone patients revealed the extent of over-scanning in individual cases: a 28-year old had 14 scans, a 42-year old had 22 scans and a 53 year old had 25 scans. The mismatch between CT risk:benefit is not isolated to kidney stones. In appendicitis, increased CT utilization has not diminished the negative appendectomy or perforation rates in children or adults. Head CT may be the rate limiting step in minimizing time-to-antibiotic in meningitis, despite the fact that brain imaging is a poor substitute for clinical intuition in detecting the rare possibility of cerebral herniation in children or adults. In trauma, 2% of pediatric patients with an abdominal CT scan (and 5% of those with an abnormal CT) underwent exploratory surgery. In adult trauma patients CT scanning accounted for 86% of the effective radiation dose with an estimated one in 500 excess deaths attributable to this level of radiation exposure over the patients’ lifetimes.
Conceptualizing the risks of CT-radiation is difficult for clinicians because of the delay between exposure and adverse outcome. The appendicitis mimicking renal colic could kill my patient this month so why worry about radiation-related malignancy which might occur in a small fraction of patients in 30 years? Furthermore, since EPs are far from the only clinicians ordering diagnostic imaging, how could any malignancy be linked to the scan I ordered decades ago. Finally, multiple sources of radiation and carcinogenic exposures exist outside of medicine so any scientist would have a difficult task assigning a cause-effect relationship. However, litigation attorneys have never been accused of scientific rigor.
Asbestos offers an interesting historical precedent for a widespread carcinogenic exposure with delayed effects. While asbestos was recognized as a lung hazard in the early 1900’s, work-related protections were not instituted until the 1930s. In 2000, asbestosis was the discharge diagnosis of 20,000 hospitalized patients and the underlying cause of death for another 2000 patients.
Just as with CT-radiation exposures, not everyone exposed to asbestosis will develop related complications. In fact, according to the American Cancer Society only about 1 in 7 asbestosis exposures will develop lung cancer with a delay extending up to 40 years. Also similar to radiation exposures, asbestosis related co-morbidities display a dose-response relationship. Now comes the scary part. Asbestos litigation has forced 80 companies into bankruptcy via a wide range of claimants alleging heterogeneous ill effects and exposures. Asbestos manufacturers and construction companies knew of the adverse effects of exposure for decades yet chose to continue using the insulation product. Similarly, radiology manufacturers, hospitals, and physicians (and patients?) realize the potential ill-effect of increasing radiation dose exposure on long-term health yet continue to deploy and utilize more CT scanners every year. On the other hand, malpractice claims for errors of omission (physician failed to order the diagnostic CT scan) are definitely not in short supply.
Bottom Line? Be cognizant of the benefits and risks of CT imaging. As with any new technology, uncertainty remains about the long-term risks of radiation exposure. Our diagnostic and prognostic uncertainty needs to be communicated to our patients and clearly documented, especially in those rare individuals who receive multiple scans over a period of time. If we are obtaining a CT scan as a means of liability protection or seeking patient-customer satisfaction rather than alleviating true diagnostic uncertainty, it would behoove us to be aware of potential long-term liability risk based upon the asbestos paradigm.
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