Noncontrast helical CT is the most sensitive and specific for the detection of renal stones

Which of the following tests is the most sensitive and specific for the detection of renal stones?

• A) KUB plain film
• B) Ultrasound
• C) Intravenous pyelography
• D) Noncontrast helical CT

The answer is D.

Compared with abdominal ultrasonography and KUB radiography, intravenous pyelography has greater sensitivity (64% to 87%) and specificity (92% to 94%) for the detection of renal calculi. Noncontrast helical CT is being used increasingly in the initial assessment of renal colic.
This imaging modality is fast and accurate, and it readily identifies all stone types in all locations. Its sensitivity (95% to 100%) and specificity (94% to 96%) suggest that it may definitively exclude stones in patients with abdominal pain.

Multiple transverse nonenhanced CT images demonstrate numerous 3-5-mm renal calculi (arrows) that were not depicted at US.