What is single kidney status?

This refers to a condition where instead of two kidneys, like everyone else, the patient has only one kidney. Single kidney status may be due to

• absence by birth or
• removed due to non functioning/ multi cystic dysplastic kidney)

Few children are born with a single kidney. How does it happen? How common is this problem?

One of the kidneys will fail to form/develop during the intra uterine period itself. So they will be born only with a single kidney. Apart from defect in the development, other causes like poorly controlled diabetes mellitus in the mother, drugs like angiotensin converting enzyme inhibitors and high dose vitamin A during pregnancy are the few risk factors for this condition

It can happen in 1 in 500 to 1000 live births. Often ultrasound (before birth) picks up the absence of a kidney. There is no need to panic, if one kidney is normally detected and the liquor volume is normal. After birth a repeat ultrasound is performed to see whether the antenatal scan findings are confirmed. If at this stage both kidneys can be detected no further testing is required. If the ultrasound after birth also confirms the single kidney status, this has to be further confirmed with a definitive test like DMSA/CT scan, as an ultrasound often misses to pick up a kidney that is located in the pelvis.

Can we have the kidney in some other part of the body instead of it in the normal position?

Yes. In some individuals, one of the kidneys will be placed in lower position and may not be detected by ultrasound.
It may also be crossed to the opposite side with both kidneys fused one below the other (crossed fused ectopia).

•  To find out this, we have other tests like DMSA/ CT.

Is it possible to live with a single kidney? Do they need kidney transplant?

You can lead a normal life with single kidney provided that the existing kidney has proper growth and function. They do not need a kidney transplantation as the single functioning kidney is often enough to clear the waste products and sustain normal life. (This is the reason how normal individuals with two kidneys are able to donate one kidney). Those with single kidney status obviously can not donate it!

Can it be familial and run in families? Do we have to screen the other family members? Do they have any associated abnormalities?

Yes. It can be familial also. It is advisable to screen the parents and siblings of children born with single kidney with ultrasound for renal anomalies. They can have associated Vesico ureteric reflux. Even if the ultrasound is normal, this needs to be ruled out if the child develops urinary tract infection with the help of a test called MCU.

Sometimes the ultrasound shows evidence for 2 kidneys with variation in size during pregnancy, but once the baby is born, doctors say that only one kidney is functioning. Is it possible to get that scenario?

Yes. Cysts in the kidneys are non functioning tissues. Hence though we see the kidney by USG as small, that may have only minimal/nil function. To prove that we may need further imaging studies.

Do the children with single kidney need regular follow up?

They should be followed up at regular interval with a pediatric nephrologist. Blood pressure, height, weight and urine protein should be checked every 6 months. Annually renal function test has to be checked. Children with renal dysfunction require more frequent visit depending upon the stage of the renal disease.

Can they participate in sports?

They can participate. But activities which are prone to cause kidney injury need to be restricted are sports like boxing, skiing, snowboarding. Apart from these, they should be encouraged to engage in some form of physical activity.

How will be the prognosis in children with single kidney?

Children with uncomplicated single kidney usually will do well. Any disease in the single existing kidney, will have varied prognosis depending on the function of that kidney. Risk of hypertension, protein loss in urine and hypertension during pregnancy are high compared to normal population.

Do they need any restriction in food intake?

They can have normal salt diet, fluids, proteins and calories which are important for their growth. In case of renal dysfunction and associated hypertension, diet should be modified restriction of salt and fluid according to the stage of the disease.

In case of illness can they be shown to any other doctor? Any contra indication for drugs?

Yes. But you should reveal the single kidney status of your child. Avoid NSAIDS(pain killers) and contrast agents.
Aminoglycosides (gentamicin/amikacin) may need careful monitoring of dose and levels to prevent damage to the only kidney functioning. Several native medications (siddha, ayurveda etc) may have multiple ingredients that could potentially damage the kidney and are best avoided.
In case of necessity, get the advice of the pediatric nephrologist.