Selection of diagnostic imaging for suspected nephrolithiasis

CT: computed tomography; BMI: body mass index.

* If further diagnosis is required following ultrasound, additional options include magnetic resonance urography and, for pregnant patients in the second or third but not first trimester, a low-dose, noncontrast CT under guidance of an obstetrician.

¶ Ultrasound reliably detects hydronephrosis, and radiography can be used to measure stone size and location. However, compared with CT, both ultrasound and radiography are less sensitive for detecting stones. Many patients who initially undergo ultrasound will require a follow-up CT to either identify a stone or to guide management.

Δ Point-of-care kidney ultrasound at the bedside is performed in many emergency departments within the United States. While it is followed by CT for the majority of cases requiring intervention, this does not result in significant care delay. In some emergency departments, an ultrasound-first approach (either emergency physician point-of-care or radiology-performed) may therefore be preferred in patients with suspected nephrolithiasis who are at low risk for serious alternative diagnoses (eg, cholecystitis, appendicitis, aortic abdominal aneurysm).