Urolithiasis is common across the world. It typically presents with flank pain with or without haematuria.
A plain abdominal (KUB) is typically performed initially with a identification rate of 60-70% as most calculi are composed of calcific components. The gold standard imaging investigation is now CT-KUB with a sensitivity rate of 99% for stones as small as 1mm. Ultrasound is largely reserved for complications such as pyonephrosis and hydronephrosis, with may merit percutaneous nephrostomy insertion.
The sensitivity and specificity of ultrasound in detecting renal calculi is much lower than CT, and is particularly poor for stones less than 3mm, with only just over a quarter seen, than are present on CT-KUB.
Ultrasound may be used first in the paediatric and pregnant population, as it may identify a calculus preventing the use of ionising radiation in these groups.