Grades of hydronephrosis (on Ultrasound imaging):

A) Mild hydronephrosis:
This images shows mild dilatation of the pelvis as well as the calyces of the right kidney suggesting mild hydronephrosis. The left kidney also appears to be affected similarly. This must be differentiated from mild dilatation of the renal pelvis alone (called splitting of the pelvis), which is physiological and transient; this means that on emptying of the urinary bladder, this appearance should disappear.

B) Moderate hydronephrosis:

The above ultrasound images show cupping of the calyces with moderate dilation (Right kidney) of the pelvis and calyces. Despite the hydronephrosis the renal parenchyma is still preserved.

C) Severe hydronephrosis:

The above sonographic images show marked dilatation of the pelvicalyces with sever thinning of the renal parenchyma. note almost total absence of normal renal tissue (cortex).