Viewpoint: Use radiographic diagnostic tests with caution

August 1, 2008

A reminder not to replace a physical examination and clinical judgment with radiographic diagnostic tests.

Sometime over the past 10 years or so, the physical examination and clinical judgment of pediatricians have been replaced by the technology developed in the field of radiology. Radiographic diagnostic tests are often extremely helpful in evaluating and managing patients, but I suggest that we use them with appropriate caution, and only when they will truly contribute additional information. Maybe a few examples of children admitted through our pediatric emergency department (ED) in the past week will suffice to make my point.

A 23-month-old boy developed unilateral cervical swelling with tenderness and fever. The swelling had developed within 24 hours, and he had no evidence of airway compromise. His examination was consistent with cervical lymphadenitis; he held his head and neck in the normal position, and he had no difficulty swallowing. The pediatric staff in the ED were confident of the diagnosis, but requested a computed tomography (CT) scan of the neck to be certain that there was no retropharyngeal abscess. The child improved and was discharged, taking oral antibiotics after three days of IV antibiotics.

An 11-week-old infant developed fever, and was found on physical examination to have erythema, swelling, and tenderness of the upper back, consistent with cellulitis. There was fluctuance in the central area of erythema. A CT scan was obtained to determine whether there was an abscess present before attempting an incision and drainage. The CT demonstrated a fluid collection in the area of the fluctuance, and incision and drainage yielded 5 cc of purulent material that grew Staphylococcus aureus.

There are many reasons to believe that radiation exposure in pediatric patients is more harmful than the same exposure in adults. Some developing tissues (eg, the thyroid, gonads, and breast tissue) are more radiosensitive in growing children than in adults. In addition, though dose adjustments to accommodate the smaller size of infants and children have been recommended for CT studies, they are not consistently employed. The result is that small bodies absorb much larger per-kilogram doses of radiation than do adults undergoing the same study. Pediatric radiologists have made a variety of recommendations for reducing the dose from radiologic studies, and it is important that pediatricians refer their patients to radiology centers that recognize and employ these techniques.1

However, the most effective method for reducing radiation exposure is to understand the relative exposure that results from various studies. For example, it has been estimated that the effective radiation dose of a CT of the chest is 68 times that of a chest x-ray. Therefore, practitioners should use these studies only when the relative benefit versus harm has been carefully considered.

It's reassuring to confirm our clinical impression using radiologic studies, and the potential diagnostic benefit of these procedures is not in question. But a thoughtful history, coupled with careful physical examination and a little patience, may avoid an increase in your patient's lifetime risk of radiation-induced cancer.

Dr. McMillan, editor-in-chief of Contemporary Pediatrics, is professor of pediatrics, vice chair for pediatric education, and director of the pediatric residency training program, Johns Hopkins University School of Medicine, Baltimore.