Swelling of the kidney due to a blockage of the urinary tract

  • Most common in very young children and elderly people
  • Gender, genetics, and lifestyle are not significant factors

Hydronephrosis results from a blockage in the urinary tract that prevents urine from flowing normally through the system. As a result, the kidney becomes swollen with urine and pressure builds up within it, preventing normal function. The condition can affect one or both kidneys and may occur suddenly or gradually.

What are the causes?

The blockage that causes hydronephrosis may be due to an abnormality of the urinary tract that is present at birth or to narrowing of the ureter (the tube that takes urine from the kidney). This narrowing may develop as a result of pressure from outside the ureter, such as that caused by a tumour or by the enlargement of the uterus during pregnancy. Hydronephrosis may also occur if a ureter is blocked by a kidney stone moving towards the bladder.

In addition, the disorder can be due to blockage of the urethra (the passage that leads from the bladder to outside the body). A blocked urethra is usually due to a urethral stricture or an enlarged prostate gland.

What are the symptoms?

If hydronephrosis results from a sudden obstruction in the urinary tract, the following symptoms may develop:

  • Severe pain in the abdomen.

  • Acute lower back pain.

  • Nausea and vomiting.

However, hydronephrosis that develops gradually over a long period of time does not usually produce the symptoms listed above. In these cases, chronic kidney failure may be the first sign that the condition exists.

People with hydronephrosis have an increased risk of urinary tract infection because bacteria are likely to multiply in urine that is not flowing freely.

How is it diagnosed?

If your doctor suspects that you have hydronephrosis, he or she may arrange for blood tests and urine tests to find out how well your kidneys are functioning. The doctor may also arrange for imaging tests, including ultrasound scanning and intravenous urography. These tests will enable the blockage in your urinary tract to be located and the cause of the obstruction determined. In some instances, hydronephrosis is detected only when another disorder, such as an enlarged prostate gland, is being investigated.

What is the treatment?

Initially, the aim of treatment is to prevent permanent damage to the kidney by relieving the pressure that has built up inside it as soon as possible. If there is a blockage in the urethra, a tube will be inserted into the bladder to drain the urine (see Bladder catheterization). If the blockage is higher in the urinary tract, a tube may be inserted directly into the affected kidney to drain the urine. Once the pressure in the kidney has been relieved, the cause of the blockage can be treated.

Hydronephrosis associated with pregnancy is usually mild and does not require treatment. The condition improves spontaneously after the birth.

What is the prognosis?

If hydronephrosis is detected early, the affected kidney tissue normally recovers once the cause has been treated. However, hydronephrosis may lead to permanent kidney damage, and chronic kidney failure may develop if both kidneys are affected.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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