I'm sorry your friend is having problems. I'll share with you what happened to me a few weeks ago.
I have been doing locarb, South Beach, since the end of april, and am loving it and my weight loss. However, I was not drinking all my water because I have a leaky bladder and did not want to have more of a leak problem than before. I was drinking maybe 30 ounces of water per day.
3 weeks ago on a Friday night, I came down with violent chills, extremely painful aches and a fever of 103.+. The fever lasted until Sunday along with the ahces and pains. I was very scared when I saw blood in my urine!! and very dark colored urine.
I went to the dr. on that Monday and told them to run a urinalysis and CBC. It came back that I had UTI and they found crytstals in my urine, calcium oxylate crystals that come from "protein". My kidneys were on strike! I took sulphur for a few days and I'm fine now. Also drank some cranberry juice and watered it down with water, afraid of adding too many carbs. The kidneys are our filtering system and without the proper amount of water and oh so much protein, they can get taxed. I honestly think that this is what happened to me and I am very pro locarb and plan on staying this way. My doctor did not tell me to stop the diet as I really need to do this!!
I know it was my own fault for not drinking the correct amount of water as its not only for weight loss that we need to drink it. Now I know better. I make sure that I have at least 64 ounces every day.
By the way, since I have lost a bunch of weight, my leaky bladder isn't so leaky anymore!!