Selection of diagnostic imaging for suspected nephrolithiasis

CT: computed tomography; BMI: body mass index.
* For pregnant patients in the third trimester who have intractable pain or fever and in whom the results of an ultrasound of the kidneys and bladder are inadequate, a low-dose, noncontrast CT under guidance of an obstetrician can also be considered to detect suspected nephrolithiasis.
¶ In patients with obesity (BMI >30 kg/m²), standard-dose CT is preferred since low-dose CT may be less reliable for detecting small stones (<2 mm) and ureteral stones.
Δ 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.