Appearance of Hydronephrosis in ultrasound

Hydronephrosis refers to a kidney with a dilated pelvis and collecting system. It can be caused by obstruction of the ureters or bladder outlet. Hydronephrosis can also result from reflux (retrograde leakage of urine from the bladder up the ureters to the renal pelvis. Rarely, some children have hydronephrosis without either obstruction or reflux. This is thought to result form abnormal smooth muscles of the renal pelvis or ureter causing ectasia.

 This ultrasound image demonstrates dilated renal calyces indicative of hydronephrosis. Chronic reflux uropathy can lead to hydronephrosis which can result in renal dysfunction as the calyces dilate and compress the renal parenchyma.
*Black arrow = renal capsule
*Black arrowhead = sinus fat
*White arrow = dilated calyx
*White arrowhead = renal cortex

This longitudinal ultrasound shows a kidney with moderate hydronephrosis. The parenchyma is relatively normal in thickness. The dilation of the collecting system extends from the renal pelvis to the calyces. This is a grade III hydronephrosis.