A mother-of-two has spoken of being given the "gift of life" when an altruistic donor gave her a kidney.

Karen Brown, 42, underwent the life-saving surgery at St George’s Hospital, in Tooting, in April, this year, after suddenly being hit with kidney failure in 2011.

Wandsworth Guardian:

The happy Brown family: Mum Karen and dad Matt with Oliver and Ella

Now she wants to raise awareness of her operation in honour of National Transplant Week, which was from July 7 to 13.

Mrs Brown, from East Grinstead, said her kidney failure came completely out of the blue and, while working for a digital company in London, she started to have really bad headaches puffy eyes.

Initially doctors treated her for sinusitis but the symptoms persisted. On her third visit, doctors tested her blood pressure and found it was sky-high and decided to monitor for 24 hours.

She said: "At 7pm the local GP rang and said ‘your kidneys are working at 5 per cent. Get straight to Brighton [Hospital] your kidneys have failed’.

"I just fell on the floor and didn’t know what was going on. I’m what is called a crash-lander. Most people have a couple of years knowing their kidneys are failing."

Mrs Brown then started a programme of dialysis and looked into having a kidney transplant but none of her friends or family were a match.

Mrs Brown set up a Facebook page, titled Brown’s Search for a Hero, through which she met people keen to help her.

However, the law stated no one could become a donor unless they were a friend or family member.

After developing a close online friendship with another woman, called Gemma, the pair worked hard to put pressure on the Human Tissue Authority to change the law.

Unfortunately Gemma was not a match for Mrs Brown but soon afterwards a kidney became available from an donor which proved a lifeline for Mrs Brown.

Wandsworth Guardian:

Karen on the road to recovery 

Mrs Brown added: "The fact that someone has gone through the operation and doesn’t know me is amazing - there are people out there and that’s why I think we should raise awareness. My window cleaner at the drop of a hat would just help in any way and I didn’t really know him.

"The kidney started working immediately on the operating table. In six months time I can write a letter to show my thanks. It is the gift of life. It is the ultimate gift. I feel like I have got my life back and the kids have too. They are so happy now and we have lots of plans for the future.

"My little girl did a dream board of things she wanted to do with me when I got my kidney. She’s also doing a run for charity and wants to raise awareness."

Mrs Brown said it was the little things that she noticed such as being able to drink cups of tea in the morning and added: "It's like Christmas every day."

Mary Budu Addo, staff nurse at St George’s Hospital, said: "Looking after transplant patients gives me inner joy and fulfillment in my work.

"I am so happy for you Karen that you have got your life back. Enjoy your new kidney."

Mrs Brown's daughter Ella, nine, is raising money for Kidney Research UK. To sponsor her visit justgiving.com/owner-email/pleasesponsor/Karen-Brown-ellas-run.