Ultrasound is the first line diagnostic tool to evaluate younger patients who present to the ED with flank pain.
Most of the time on ultrasound, you will not see the actual kidney stone. More often, you will see associated signs such as hydronephrosis.
In a patient with hydronephrosis, the normally hyperechoic renal pelvis will become anechoic. With increased severity of the hydronephrosis, you can have complete distortion of the kidney.
You can tell the difference between hydronephrosis and a renal vein by placing color doppler over the image. Hydronephrosis will not have flow.
Moore CL, Carpenter CR, Heilbrun ML, et al. Imaging in Suspected Renal Colic: Systematic Review of the Literature and Multispecialty Consensus. J Urol. 2019 Sep;202(3):475-483. doi: 10.1097/JU.0000000000000342.
