By JULIE MOULT

Last updated at 00:58 18 February 2008

After Laura Moon started suffering stomach pains, doctors decided to carry out an ultrasound scan on the teenager.

When they saw the results, they were astounded.

For the scan revealed that she had four kidneys. The 18-year-old is now hoping to donate the extra organs for transplant operations.

Only a handful of people in the UK have four kidneys, although having three is relatively common. But Laura's case is especially unusual because all four are fully formed and functional.

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Laura Moon discovered she had four kidneys when she had an ultrasound

Laura, a customer services adviser from Leeds, said: "I think if I've got four, I don't need all four. Why not donate if there's someone else in need?

"I hope I can help somebody else while I am young. I will do everything in my power to become a donor."

It is not known why people develop multiple, or duplex, organs but one in 125 people have one extra kidney, normally a partial organ.

Laura's condition often causes the patient no problems, although sufferers can be more prone to urinary infections.

She discovered she had the unusual anatomy six months ago when she was undergoing tests following a road accident.

"I was in a car crash a year ago and six months later I began having a lot of pain in my stomach. My GP referred me to the hospital for a scan."

Doctors at Seacroft Hospital in Leeds carried out the procedure. "I realised that the doctor scanning me hadn't said anything for a long time. I thought he was going to give me bad news," said Laura. "The guy just said 'You have got four kidneys'.

"He measured them and I have two which are 14cm and two which are 9cm.

"Then he also asked if I would mind if he took some photos to show to university students." Transplant surgeon Niaz Ahmad, from Leeds Teaching Hospitals NHS Trust, said parts of the kidney system could be duplicated but he had never seen anyone with four full kidney systems.

"To have completely duplex kidneys on both sides is extremely rare," he said.

By coincidence Laura's aunt Dawn Fry has a third kidney - although the pair are not blood related.

Consultant urological surgeon Dr Robyn Webber, of Fife Acute Hospitals, said many extra kidneys are fully functional, meaning Laura should be able to donate.

Dr Webber added: "It is a relatively rare condition. Ordinarily they are left alone unless the patient is suffering any problems. But Laura will be able to manage perfectly well with two so assuming they are working correctly there is no reason why she shouldn't donate them."

According to the UK Transplant organisation, living donor kidney transplants now represent more than one in four of all such operations.