Images of hydronephrosis. Both patient presentations involved acute onset flank pain. In the workup, bedside US was used to further evaluate for suspected pathology.
The images below show the kidney in long-axis. Note the large echo-free area in the echogenic renal pelvis. Both images capture moderate degrees of hydronephrosis – as commonly seen in obstructive uropathy. The doctors went one step further by using Doppler imaging to show the echo-free area of the renal pelvis was not vascular in origin (absence of color flow) but, rather, representative of urinary dilation of the renal pelvis.
US does not commonly detect renal stones. Instead, it has an excellent ability to detect hydronephrosis (see below schematic representation for the degrees of hydronephrosis).
The presence of unilateral hydronephrosis or hydroureter in the setting of hematuria and acute flank pain is very sensitive for the presence of a ureteral stone. Comparison between R and L kidneys should always be done. See the cartoon representation for a visual reference of the degrees of hydronephrosis.