American Board of Internal Medicine (ABIM) Certification Practice Exam

In cases of suspected nephrolithiasis, what does a negative ultrasound indicate?

1. No kidney stones present

2. Further imaging with CT is not necessary

3. Likely need for immediate surgery

4. Need for further imaging like a noncontrast helical CT

The correct answer is: Need for further imaging like a noncontrast helical CT

In the context of suspected nephrolithiasis, a negative ultrasound indicates that while stones may not be visualized, it does not completely rule out the presence of kidney stones. Ultrasound is a useful initial imaging modality, especially in certain populations, but its sensitivity can be limited. Therefore, a negative ultrasound does not negate the possibility of nephrolithiasis. If the clinical suspicion for kidney stones remains high despite a negative ultrasound, further imaging is warranted. Non-contrast helical CT is considered the gold standard for diagnosing nephrolithiasis due to its high sensitivity and specificity. This imaging technique can identify stones that might not be visible on ultrasound and provide additional information on the size and location of stones. Thus, a negative ultrasound suggests the need for follow-up imaging, particularly a non-contrast helical CT, to ensure a comprehensive evaluation of the patient’s condition.