Diagnostic Imaging: Appropriate and Safe Use


Am Fam Physician. 2021 Jan 1;103(1):42-50.

Published online November 23, 2020.

Author disclosure: No relevant financial affiliations.

The use of diagnostic radiography has doubled in the past two decades. Image Gently (children) and Image Wisely (adults) are multidisciplinary initiatives that seek to reduce radiation exposure by eliminating unnecessary procedures and offering best practices. Patients with an estimated glomerular filtration rate less than 30 mL per minute per 1.73 m2 may have increased risk of nephropathy when exposed to iodinated contrast media and increased risk of nephrogenic systemic fibrosis when exposed to gadolinium-based contrast agents. American College of Radiology Appropriateness Criteria can help guide specific diagnostic imaging choices. Noncontrast head computed tomography is the first-line modality when a stroke is suspected. Magnetic resonance imaging stroke protocols and computed tomography perfusion scans can augment evaluation and potentially expand pharmacologic and endovascular therapy timeframes. Imaging should be avoided in patients with uncomplicated headache syndromes unless the history or physical examination reveals red flag features. Cardiac computed tomography angiography, stress echocardiography, and myocardial perfusion scintigraphy (nuclear stress test) are appropriate for patients with chest pain and low to intermediate cardiovascular risk and have comparable sensitivity and specificity. Computed tomography pulmonary angiography is the preferred test for high-risk patients or those with a positive d-dimer test result, and ventilation-perfusion scintigraphy is reserved for patients with an estimated glomerular filtration rate less than 30 mL per minute per 1.73 m2 or a known contrast allergy. Computed tomography with intravenous contrast is preferred for evaluating adults with suspected appendicitis; however, ultrasonography should precede computed tomography in children, and definitive treatment should be initiated if positive. Ultrasonography is the first-line modality for assessing right upper quadrant pain suggestive of biliary disease. Mass size and patient age dictate surveillance recommendations for adnexal masses. Imaging should not be performed for acute (less than six weeks) low back pain unless red flag features are found on patient history. Ultrasonography should be used for the evaluation of suspicious thyroid nodules identified incidentally on computed tomography.

Estimates suggest that 30% of all U.S. health expenditures are a result of waste, with approximately $100 billion lost on overtreatment and low-value care; inappropriate radiography is a major component.1 The use of advanced imaging, including computed tomography (CT), magnetic resonance imaging (MRI), ultrasonography, and nuclear medicine, has doubled in a 16-year period, accounting for 11% of allowed Medicare charges in 2018.2,3 Awareness of risks, benefits, and recommendations related to radiography enhances shared decision-making and reduces unnecessary testing.2,4

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Clinical recommendationEvidence ratingComments

Follow reduced radiation protocols from the Image Wisely (adults) and Image Gently (children) initiatives, and use American College of Radiology Appropriateness Criteria when making diagnostic imaging decisions.816


Expert opinion and longitudinal cohort studies

Prophylactic isotonic crystalloid volume expansion is recommended in patients with an eGFR less than 30 mL per minute per 1.73 m2 to prevent contrast-induced nephropathy.2128


Large retrospective propensity-matched studies demonstrate no significant effect; expert opinion and consensus guidelines still encourage hydration in these patients

An eGFR less than 30 mL per minute per 1.73 m2 is a relative contraindication for the use of gadolinium-based contrast agents.2931


Expert opinion and consensus guidelines

Do not perform imaging in patients with primary headache disorders without new or progressive features who have normal neurologic examination findings.37,52,53


Expert opinion and consensus guidelines

A clinical probability assessment tool should be used to determine pretest probability before performing imaging in patients with suspected pulmonary embolism. The Pulmonary Embolism Rule-out Criteria or d-dimer testing can be used to avoid unnecessary computed tomography pulmonary angiography in some low- or intermediate-risk patients.5760


Expert opinion and well-designed randomized clinical trials with disease-oriented outcomes

Do not perform plain chest radiography in asymptomatic patients for preoperative evaluations or for baseline testing during hospitalization.42,52,72,73


Large meta-analysis of 20 trials with disease-oriented outcomes; expert opinion

Do not perform imaging in patients with acute (less than six weeks) low back pain and no red flag findings on history or physical examination.47,75,76


Numerous randomized clinical trials and systematic reviews and meta-analyses

eGFR = estimated glo

The Authors

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BRIAN FORD, MD, FAAFP, is an assistant professor in the Department of Family Medicine at the Uniformed Services University of the Health Sciences, Bethesda, Md. At the time this article was written, he was a faculty physician at Naval Hospital Camp Pendleton, Calif....

MICHAEL DORE, MD, is a staff physician at Naval Hospital Bremerton, Wash.

PAUL MOULLET, DO, is a staff physician at Naval Health Clinic Lemoore, Calif.

Address correspondence to Brian Ford, MD, FAAFP, 4301 Jones Bridge Road, Bethesda, MD 20814 (email: brian.ford@usuhs.edu). Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


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