Kidney Swelling (Hydronephrosis)

What is kidney swelling?

Hydronephrosis is the distention or swelling of the kidney as urine builds up in the kidney (hydro = water, nephros = kidney). This is due to a partial or complete obstruction of the flow of urine at the upper end of the ureter or tube that brings the urine from the kidney to the bladder. Hydronephrosis can sometimes develop in children; however, most often babies are born with the condition. It is one of the common abnormalities of the urinary tract. ​

What are the symptoms of kidney swelling?

If hydronephrosis is left undiagnosed and untreated, some children will present with a large stomach bulge and perhaps pain, from a huge, swollen kidney. Often when picked up at this stage, there is not much kidney function left in that kidney. The other kidney is usually normal.

What causes kidney swelling (hydronephrosis)?

Hydronephrosis of one kidney is most commonly caused by an incomplete blockage at the junction between the kidney urine collecting system, and the urine drain pipe (pelvicalyceal system and ureter). This is called a PUJO. This is an in-born condition and is not known to be inherited or related to food or behaviour during pregnancy.

Other causes of hydronephrosis include the backflow of urine from the bladder into the kidneys or a blockage of the lower end of the ureter.

How is kidney swelling (hydronephrosis)?​

In unborn babies, this condition can be diagnosed by an ultrasound scan of the expecting mother. Hydronephrosis does not usually affect the pregnancy, and the delivery should proceed as planned. The condition will then be confirmed by a repeat ultrasound of the baby’s kidney on the second or third day of life. On an ultrasound the kidney tissue may be distended and squashed, and the urine drainage system will appear very ballooned and dilated.