Kidney Swelling (Hydronephrosis)

What is kidney swelling (hydronephrosis)?

Hydronephrosis describes the abnormal distention or swelling of one or both kidneys when urine accumulates in the kidney and stretches it. This is due to an obstruction to the normal urine flow and sometimes due to an abnormal backflow or reflux of urine from the bladder up to the kidneys, a condition termed vesicoureteric reflux (VUR). Hydronephrosis is diagnosed clinically based on findings from a kidney ultrasound.

Hydronephrosis can be congenital (born with) and is one of the most common abnormalities that can be detected on antenatal ultrasound of pregnant mothers.

When occurring in adults, it is often a complication of an acquired condition that blocks the urine flow (e.g., renal stones, enlarged prostate). Acquired conditions resulting in hydronephrosis are not common in children. Thus, the causes of childhood hydronephrosis may be different from that in adults and require a different management approach.​

What are the symptoms of kidney swelling (hydronephrosis)?

Mild cases of childhood hydronephrosis are asymptomatic. If left undiagnosed and untreated, some children will present with a bulging abdomen and occasionally loin pain from the huge swollen kidney. When picked up at this stage, there is often little kidney function left in that kidney and the kidney is no more salvageable.

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 pelvic-ureteric junction obstruction (PUJO), which 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) diagnosed?

​Hydronephrosis is often silent in children, but ultrasound screening can easily pick up the abnormality. Renal ultrasound screening is done routinely in two instances:

1. Antenatal checkup of pregnant mothers
2. Following febrile urinary tract infection (UTI)

When detected, the severity of hydronephrosis can range from mild to severe distension. In severe cases, the hydrostatic pressure from prolonged or chronic accumulation of urine, can cause compression of the kidney tissues which overtime can progress to permanent damage of the kidneys.

Mild cases are asymptomatic but need regular follow up and serial ultrasound to track the progress of the distension.

Preventing congenital hydronephrosis from progressing to kidney damage

It is important to undergo routine antenatal ultrasound during pregnancy. If noted to have kidney swelling, it is important to have follow-up ultrasound. The condition can be confirmed by a repeat ultrasound of the baby’s kidney on the second or third day of life. Hydronephrosis does not usually affect the pregnancy and the delivery should proceed as planned.

Following an episode of UTI that is accompanied by fever, a kidney ultrasound is routinely done to screen for kidney abnormalities and possible underlying hydronephrosis and sometimes hydroureter which is similar swelling in the lower part of the urinary tract. Hydronephrosis and hydroureter caused by obstruction and VUR predispose patient to recurrent UTI and higher risks of irreversible kidney damage due to scarring.

More focused imaging studies will be needed to reveal whether there is underlying urinary tract obstruction or VUR. Depending on the severity of the underlying conditions, surgery may be required to prevent damage to the kidneys.

If kidney stones were found on kidney ultrasound, tests to determine the causes for the stone formation and further treatment may be necessary. There are rare cases of hereditary stone diseases and genetic testing may be necessary to clinch a diagnosis. Adequate hydration is important in stone disease.

How is kidney swelling (hydronephrosis) treated?

Treatment for hydronephrosis depends on the underlying cause.

Babies with hydronephrosis, especially in milder cases, will sometimes improve with time without surgery. However, this requires regular monitoring with kidney ultrasound to assess the progress.

Surgery

Surgical treatment is indicated in two instances:

1. If there is progressive increase in the swelling and further scans showed obstruction
2. If it is complicated by UTI

When a diagnosis of an obstruction at the upper end of the ureter termed pelvic-ureteric junction obstruction (PUJO) – the most common congenital urinary tract obstruction – is made, an operation called pyeloplasty will be needed to relieve the obstruction and re-establish a smooth urine flow as well as relieve the back pressure on the kidney. This is a major operation, but most often has a high cure rate and a low chance of any complications.

Your doctor will give you a management plan for hydronephrosis and adherence to the plan is prudent to ensure best outcome.