The Fighter: Kirsteen Lupton had her first operation the day she was born.

Now, 14 years on, the determined schoolgirl, who has raised £1m for charity lets rip about God, death, family crises – and living life to the full

I HAVE interviewed many remarkable people but don't usually have to wait for them to get home from school. Kirsteen Lupton is the exception, and she is exceptional. She was born with bladder exstrophy, a rare condition in which that organ is on the outside of the body. Born in the Queen Mother's Hospital, Glasgow, she had surgery that day, the first of many major procedures that have stretched through her early life like an archipelago of pain and fear. She has had far more operations than birthdays. Kirsteen is 14.

She lives on a quiet street in Milngavie, on the edge of the East Dunbartonshire countryside, with her parents, Jill and Martin, and her elder brothers, Kenneth and Martin Jr. On the walls of their home are photographs of Kirsteen with celebrities she has met in the course of raising over 1m for Great Ormond Street, the children's hospital in London which she credits with making her life bearable. There's Kirsteen with Jude Law. There she is with Cat Deeley. There's probably a picture of her with McFly somewhere, as they gave her a signed guitar to auction. Like many teenagers, though, her loyalties are fickle and she now prefers the Red Hot Chili Peppers. To admit to liking McFly is to risk a slagging. "They are lovely people, though," she says, damning with faint praise.

As far as things like that go, Kirsteen is a regular teenager. Outside of school, her life can be summed up in four words: "Music. Friends. Shopping. Sleepovers." I had reservations about interviewing a 14-year-old. I worried she'd hide behind her hair, mumbling and shy, but she is forceful, confident and articulate; quick to laughter and anger. Kirsteen is sitting on the couch beside her mother. Jill is 49. Martin, a 47-year-old police officer, is held up at work, but arrives later. Martin Jr is upstairs. Kenneth is studying at Glasgow University. I ask first about the experience of working on Pride of Britain, a memoir told through Kirsteen's recollections, as well as those of her family. Kirsteen says working on the book made her realise how much her parents had suffered. For Jill, "It brought back all the memories I had shut out. When I read the book now, I think, 'How did I get through that stage in my life?'"

Kirsteen was born on October 27, 1993. Jill worried throughout the pregnancy that something was wrong; she had five scans, the last on the day before she gave birth, but there was no indication of any problem. Minutes after the delivery, a doctor approached the Luptons, offered his congratulations, and said: "Unfortunately, there's a problem. We think we can see her bladder." It was shocking to hear; 11 words hitting like punches to the stomach. For Martin, it was like some weird plot twist from a bad film; the evening before, he had seen a documentary on the condition.

Bladder exstrophy occurs in around one in every 50,000 births worldwide. The cause is unknown, but it is thought to happen at around the sixth week of development if the pelvic bone fails to set properly. The condition is not life-threatening, but complex surgery is required, and this has attendant risks. The worst moment came in September 2000 when Kirsteen was almost seven. Following an operation at Great Ormond Street, it was believed that a hole had opened up between her bowel and bladder; to give this time to heal, she was fed by drip for over a week. She lost a great deal of weight, dropping to one and a half stone. Eventually it was discovered that the plastic tube carrying nutrients into her bloodstream had become infected. Her surgeon Philip Ransley decided he would have to operate in order to identify and correct the problem, but she had become so weak that surgery was a huge risk.

Kirsteen, though still so young, was resigned to her imminent death. Drifting in and out of consciousness, she told her mother, "I'm going to die and I'm scared. But tell Daddy I love him and I'll miss him." Martin had just returned to Scotland, unaware that his daughter's condition was taking such a serious turn. Jill phoning him with this message he remembers as the worst experience of his life.

I ask Kirsteen about what she said. It seems a remarkable statement for a six-year-old – there's a calmness to it, a quiet acceptance and settling of affairs that you might expect in an elderly person who felt happy to have lived a long and full life. "Because I said it, I don't think it's remarkable," she replies. "I'm happy I was able to say stuff like that at that age. I think it's because of what I'd been through for so long. Me dying was something that was thought about a lot. It probably wasn't as big a thing as maybe one of my brothers or my mum dying, because I had more chance of dying than anyone else. I honestly did believe for ages that I was going to die."

Happily, Ransley's operation was a success and Kirsteen was finally able to get on with trying to live a normal life. She was able to stop wearing nappies, and she could feel herself growing stronger, both physically and mentally. She still has to drain her bladder every four hours, using a catheter, which she hates, but says that her medical condition doesn't get in the way of her life or make her consider herself fragile. She is studying for standard grades at Douglas Academy and, at weekends, she's one of those girls hanging out of a hired pink limo and shrieking with happiness.

Has her proximity to death changed her attitude to life? "Yes," she says. "I had a friend, Sammy, with leukaemia, who nearly died as well, and people always say to us, 'You two are mental,' because we'll do anything and everything for fun and don't care what other people think. I had a friend called Alex in the hospital and he died. I think of him a lot and I feel as if I'm trying to have a fun life for him because he can't any more. Seeing people you have become close to dying isn't easy. So I try to make the most of my life." Also, at the back of her mind, pushed into a far corner, is the unwanted but ever-present notion that one day her own condition could worsen.

What's fascinating about Kirsteen is the way that hospitals and surgery dominated and defined her early life. Operations were the milestones. She had six of them before she was two, and therefore her earliest memories are medical. We might associate infancy with certain remembered smells – dad's aftershave, candyfloss at the shows, soup cooking in gran's house. Kirsteen recalls the antiseptic smell of theatre, the sight and feel of the anaesthetising mask placed over her face. She remembers, with resentment, asking a surgeon in Yorkhill, the children's hospital in Glasgow, how long she would have to stay and his reply, "How long is a piece of string?"

Kirsteen was too young to understand that the treatment was for her own good in the long term. She couldn't understand why she was being taken to a place that made her feel sore. "I can remember hating Yorkhill with a passion," she says. "For me, it meant pain and illness; coming home meant happiness and being with family and not being different. All my impressions of hospital were horrible, and I always felt my surgeon in Yorkhill was better than me and had so much more power over me than my own parents did, and that scared me a lot. I suppose I got angry at my parents for not stopping this. I felt they weren't even trying for me. I'd think, 'Why should I even try when Mum and Dad don't care that I'm in pain?'"

I can't help but wonder what sort of lasting impact this might have. Kirsteen has been left with plenty of physical scars, but what about psychologically? To experience agony and anguish at a young age, to face the prospect of your own death as well as grieving for a friend your own age, surely that leaves a mark? "I know I'm really lucky to be alive and have the friends and family I do," she says. "I don't know if I am just bottling everything up and one day it will explode or whether I am properly over it. Reading the book was pretty hard for me, and some of my friends who had sneak previews took it pretty badly and started crying. That was hard to see. I suppose I'm just trying to take it in my stride and see where I end up in life. Once school's over, and as my life goes on, I think it might hit me just how hard I've had to try to get to where I am."

Kirsteen is unquestionably a courageous girl with special qualities. The Pride of Britain award she won in 2006 is testament to that. But her parents have had to be incredibly strong and dedicated in caring for her. Most parents will recognise that when you first have children, along with love there is also a sense of fear. For Jill and Martin, this anxiety was amplified by having to cope with their daughter's illness, something they feel they accomplished with little help from their families.

"We were very isolated," says Jill. "Martin's mum and dad came up from Merseyside for a week, and my dad was very ill but he still came along to the hospital; he was wonderful and got on great with Kirsteen. But my mother was a very vicious person. She was the biggest hypochondriac herself, but if anybody had anything wrong with them, she thought it wasn't worth them being alive. My sister Gladys felt the same way. So I didn't see them for seven months after Kirsteen was born. They didn't want to know me, and I just had to get on with things. It was only after my mother died last year that the anger really hit me. Now I'll never get the answers I wanted."

Answers to questions such as why her mother, Gay, took the attitude she did. "She was like that ever since I was very young," Jill continues, thinking back to her upbringing in Old Kilpatrick. "There was a wee girl in the village who had polio and wore big callipers. My mother would say things like, 'Don't go near her. She's dirty. She drank puddle water. That's why she's got that condition.' And children with Down's syndrome, she didn't have any time for them. She hated anyone with disabilities."

The day after Kirsteen was born, Gay went to the Erskine Bridge and threatened to throw herself off. Jill's anger towards her mother is so intense she is seeing a psychiatrist and taking diazepam. The problem is that, with her mother gone, her anger has no target. "Now she's dead, I can't get back at her," she says in a near whisper. Kirsteen didn't realise, while her grandmother was alive, how she felt about disability. But she too seems very angry about the way her parents were left to cope on their own. She speaks very intensely about her aunts and uncle, and her grandparents on her father's side, and says she has not forgiven their absence.

Ironically, Jill's troubled relationship with her own mother ensured that she would cherish her daughter, regardless of her problems. She says that Gay had wanted four boys and did not make any secret of her disappointment at having three girls and only one son. She says Gay told her she didn't like her. In reaction, she has consciously taken a different approach with her own children. "Whatever I do, I think, 'What would my mother do?' and I do the opposite." Kirsteen, as a result, has been loved unconditionally.

But the stress of her upbringing has had an impact on Jill's relationship with Martin. It's as if they went into crisis mode when she was born and have never quite managed to come out. "We've coped with it in such different ways," says Jill. "In lots of ways, it has separated us. We never really spoke to each other about how we were coping. I would get angry at him and deliberately take things he said the wrong way so I could have a fight with him, because I had to take it all out on somebody.

"A terrific number of couples split up when something like this happens. Kirsteen knows we've spoken about splitting up. It did put a terrific amount of pressure on us, which is still there. It doesn't just disappear."

Kirsteen nods. "Yeah, there's been a few times when Mum and Dad have sat me and Kenneth down and said, 'Guys, we can't do this any more.' But then they'll try to talk it through and it will be better. But me, Kenneth and Baggy (her nickname for her brother Martin Jr] have been expecting it for a long time, to be honest. I don't think it would surprise me if they did split up."

Martin later talks about the pressure. "Kirsteen's care needs were so great that the main theme running through our lives was getting her through her next surgical procedure and trying to retain a semblance of normal family life for our boys. I know it's not the same, but Madeleine McCann's parents said that they had to keep going for the sake of their twins, and I know what they mean. You have to maintain what is, perhaps, an artificial faade."

When Kirsteen was born, Jill became convinced she must have done something wrong during the pregnancy to cause the condition. Eaten the wrong thing. Lifted a heavy object. Something like that. She was being worn down by guilt, and so when someone mentioned the theory that bladder exstrophy could, in fact, be passed down the male line, she exploded at Martin. "I said, 'You've never blamed yourself!' But he is right, it's nobody's fault. One of our friends said, 'If you want to blame anybody, blame God.'" And did she? "Well, I stopped going to church. I believe there's something there, but I don't believe it's a caring God."

Kirsteen interrupts. "I have strong feelings about God. My RE teacher tried to tell me rubbish like, 'If there wasn't suffering, there wouldn't be compassion.' Tell that to those who are suffering! If you ask anyone who is suffering, 'Do you think God's caring?', they'll say, 'No, because then he wouldn't be putting me through this.'"

When Kirsteen, aged seven, was told that her friend, Alex, had died of cancer, she threw her school Bible in the bin. "Why would God put Alex and his family through that when he knew that, in the end, Alex was just going to die?" she asks with real rage. Religious people have told her that God picked her to have this condition because he knew she was strong enough to cope. She doesn't think much of that theory.

Until Kirsteen was six, all her medical procedures took place at Yorkhill. But the Luptons became unsatisfied with the treatment they received, and eventually, through their local health board, got funding to have Kirsteen treated in London. "Great Ormond Street was able to get our daughter to the stage she's at now," says Martin. Kirsteen adds, "Great Ormond Street was able to help me and Yorkhill wasn't. I can't be any more diplomatic than that."

A spokesperson for Yorkhill said, "We are sorry the family feel that the care Kirsteen received did not meet their expectations."

However, Kirsteen has been inspired by her experience of Great Ormond Street to become a doctor herself, grades permitting, and specialise in her own condition.

She's an interesting girl, surprising in her passions and prejudices. I get the feeling, though, that she remains something of a mystery to herself. That, of course, is not unconnected with being 14; self-knowledge is a bit much to expect from someone so young. But still, I ask whether she feels different from other people – not physically, but whether she senses an inner strength and composure which sets her apart.

"I just have a lot of determination," she says. "A lot of people do feel there might be something special in me, but I don't know what that is. All I do is get up in the morning and try my best." r

Pride of Britain (Virgin Books, 12.99) by Kirsteen Lupton and family is out now