Mohamed Nanji's kidney problems started when he was a teenager in Kenya. Although he's been living with a transplanted kidney for more than 10 years, it hasn't been easy.
"When I was a teenager in Kenya, I kept getting repeated infections. The doctors discovered that my right kidney had two tubes connecting it to the bladder, rather than one. This put pressure on my back and gave me the infections.
"I was told to look after myself and I would be all right. I am a clinical scientist and I came to study in the UK. I had my kidney function tested regularly at Guy's Hospital in London, but gradually it got worse.
"I was told by the doctors at Guy's that I was getting to the point where I would soon need a transplant or dialysis. My sister was my only relation and she agreed to donate a kidney. She was quite happy about it at the time and was a perfect match.
"A year later, they told me I should ask my sister to come to the UK because I would have to have the transplant within a few weeks. When I contacted her, she didn't get back to me. A couple of months later, I phoned again and she told me she had changed her mind. She didn't give any reason.
"It was obviously very upsetting, but the whole situation was made worse because she didn't let me know until the last minute. I hadn't planned to start dialysis because my sister was such a perfect match for transplant, but I had no choice.
"When I went to the hospital to have my first dialysis, the doctors found that I was at the end stage of renal failure and admitted me straight away. I had a traumatic two weeks in hospital as they tried to keep me alive. I suffered bleeding episodes that lasted up to 12 hours and I grew very weak.
"Eventually, I was able to leave. I continued working as best I could and soon began doing my dialysis at home. It was difficult, but better than going to the hospital three times a week until 4am.
"Later the next year, my strength had returned and I went on the transplant list. In December, I was called in to have the operation, but it didn't go smoothly. I had to go back into the operating theatre three times because there was so much bleeding.
"The doctors thought the surgery had failed and were about to put me back on dialysis when suddenly the kidney began to work. Years later, it's still going strong. Now, I live a normal life again."