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This page covers two main topics:
Duplex Kidney Systems, and Obstructions of the Urinary Tract.

Double Or Duplex Kidney Abnormalities

During pregnancy there is a reduplication of one or more of the kidneys or associated urinary tracts during the period when they were forming in early pregnancy.


  • Smelly urine
  • Failure to thrive (poor weight gain)
  • Frequent urine infections
  • Fever
  • Generally unwell
  • Diarrhoea

Investigations – what will the doctors do?
First, your GP may do a simple urine check to see whether there is any infection present.

If this shows an infection present, then they will send you off for other investigations of the urinary systems.

There are two main investigations that will take place:

M.C.U. – Micturating Cysto-Urethrogram
This is where they insert a tube (catheter) into the bladder through the urethra. The bladder is slowly filled with fluid and then pictures are taken. When the x-ray examination is done it is usual for the bladder to be filled until the urine passes back down around the catheter and then the catheter is removed.

Pictures will show the structure of the urethra. Some children have a blockage to this tube. This test is very good and sensitive for detecting ureteric reflux, which is common if your child has a duplex system.

This is a harmless and painless examination. Many women have this during pregnancy. It shows if the kidneys are a normal shape and size and are in a normal position. It will usually show if the flow of urine is obstructed or if kidney stones are present.

If your child has reflux with the duplex kidney or urinary tract system, they will be treated with antibiotics to prevent any infection from occurring. They will usually be given a low dose of an antibiotic for a year to see if the reflux disappears.

Surgery is sometimes needed to remove part or the whole of the duplex system if there are any problems with obstructions or any other complications of the urinary system.

Obstructions Of The Urinary Tract
These can occur in any part of the urinary tract system and can cause damage to the kidneys if they are not picked up early.

If there is obstruction to the flow of urine there is the danger of infection resulting and scarring occurring.

Common sites for Urinary Obstructions to Occur

  1. An obstruction is at the junction of the pelvis and ureter, often referred to as the (pelvi-ureteric junction) obstruction. This is usually congenital, but may only come to be noticed later. The pelvis of the kidney will blow up and the kidney substance becomes very thin due to the pressure from the urine been pushed back into the kidneys.
  2. An obstruction in the ureter. This is usually an acquired form of obstruction from a variety of causes, which can appear within the ureter (stones), in the wall of the ureter (tumours, inflammation) or pressing on the ureter (tumours, inflammation).
  3. An obstruction is at the junction of the ureter and the bladder. This is often congenital but may be the result of surgery to cure reflux, if the ureter is sewn in too tightly. It may also result from a thick bladder wall, as shown on the left of the diagram over the page.
  4. Another form of obstruction is found in men from the result of prostatic enlargement.
  5. An obstruction in the urethra, the outlet from the bladder. It is usually a congenial abnormality, or as the result of infection.

If the obstruction persists at sites 3,4, and 5 then the bladder wall thickens with small sacks bulging out at weak spots on the wall.

The conditions may be noticed through urinary infections.

The treatment for urinary tract obstructions is usually surgical, and needs to be done to prevent any further damage from occurring from the backflow of urine into the kidney tissue.

Investigations to discover the obstructions:
These are usually the same as most other kidney problems.

The specialist will usually do an ultrasound and/or an MCU (micturating cysto-urethrogram). This is to give them a clear picture of the urinary system to see where the obstruction is.

In this test a substance that contains iodine and can be seen on an x-ray, is injected into a vein. Normally iodine passes through the kidneys and into the urine. On x-ray it is possible to see in some detail the size and shape of the kidneys, whether there is any blockage to the urine flow from the kidneys and even sometimes, the bladder. The doctor will ask you if your child has any allergies as some people are allergic to iodine.

A similar test can be done to see if the kidney is functioning normally. This test uses a weak radioactive substance attached to a chemical that normally passes through the kidneys. This test may be referred to as a radioisotope scan or scintigraphy.

The amount of radiation your child is exposed to with these tests is much less than that of an x-ray.

Children with abnormal urinary tracts may behave differently to other children. They are usually late in becoming dry during the day and may continue to have enuresis (bedwetting at night) into later childhood.

Outlook after treatment:
If there is no damage to the kidney with scarring from the obstruction or reflux then the outlook is good.

If there is scarring on the kidneys your specialist will want to check your child on a regular basis to ensure there are no long term problems.

They will discuss this with you when you see them for results from the tests.

This advice is only intended as a guideline and is very general. Please check with your specialist or GP if you have any questions relating to your child’s condition.


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