Two-year-old Omar's parents gave up their home, their life savings and travelled over 2,000 miles to get him the vital liver surgery that could save his life.
Mamoud had little option left
Omar's bones were very weak, and when he was 10 months old he stopped growing. His brother, only one year his senior, was twice his size.
Omar's liver disease prevented him absorbing nutrients from his food so his body was not able to develop normally.
His health was deteriorating rapidly, and without a liver transplant he would die within months.
His family decided that they must travel from their home in Beirut to London for a transplant.
The trip was not cheap. The family were forced to borrow heavily to finance it, and have debts of over £500,000.
"We don't have anything left," said Omar's mother Rania. "When we go home we will have to start from scratch. But for us this is nothing compared with having Omar safe and sound in front of us."
The surgery was to be conducted by Nigel Heaton, one of the UK's leading liver surgeons who has headed the liver unit at London's King's College Hospital for a decade.
He has conducted 800 liver transplants, but still finds that the job gives him immense satisfaction.
Omar had months to live
"I still love doing it, it is a drug, it is a challenge," he said.
The big problem, however, is that there is a serious shortage of donor organs available. Omar was not an NHS patient, and so was at the bottom of the list. Five children were ahead of him, and he was getting sicker.
Finally, and despite the risk, Omar's father Mamoud decided that the only solution was to donate a piece of his own liver tissue to his son.
He was in luck. Dr Heaton's team is only one in the UK which performs living relation liver transplants. Because of the risk, most surgeons prefer to use an organ taken from a dead donor.
Initially, and much to the family's anguish, the operation had to be cancelled because of a lack of intensive care beds.
Waiting for the operation was not only expensive for the family, it was putting Omar's safety increasingly in peril.
Nigel Heaton has massive experience
In total, the operation was cancelled three times. Then, suddenly, after months of waiting, the family received a call summoning them to the hospital.
Dr Heaton told the family that although the risk of things going wrong was small, there was a definite risk.
"I'm not worried about the risk of the surgery for me," said Mamoud. "But I am worried about the risk for Omar.
"Yesterday I went to bed and said "God, I am not asking for wealth, I'm asking for health. I'm just asking for my family to live in peace."
Dr Heaton was very conscious of the pressure on his shoulders.
"Mamoud is risking his life to ensure that his son gets a functioning piece of liver," he said. "We have got to try to make sure that it functions as well as possible."
The surgical team successfully removed about 25% of Mamoud's liver during a five hour operation. What is left will grow back to its original size within three months.
Rania was overcome with emotion
While Mamoud was still on the operating table, medical attention was turned to Omar.
His diseased liver turned out to be abnormally large, and dark green. A healthy liver is pinkish-brown.
After two hours of painstaking surgery, Omar's liver could be removed, and his father's healthy tissue transplanted.
It was too big for the little boy at first, but will shrink to the right size over the coming weeks.
The surgery appeared to be a success, and the liver seemed to be working well.
"I am afraid to go and see him, because I don't know what I will see," said Rania, who, nevertheless was over-joyed at the good news.
"They would have to invent a new word to describe this feeling."
The weeks following the double operation were critical, both for Omar and Mamoud.
Omar's new liver
But eight weeks after his transplant, Omar has impressed doctors with his recovery. His father has already gone back to Beirut to start paying off the family's debts.
Omar will soon follow. Dr Heaton said: "It is nice to see him going home.
"Omar will be one of the children I will remember clearly. But there are always other people to worry about. It is important that we do worry about them, because it is a sign that we do care.
"You can't look after patients in this specialty without caring."
Omar's story is featured on Your Life in their Hands on BBC1 on Monday at 2100GMT.