There are four main groups of kidney stones: calcium, uric acid, struvite or infection, and cystine stones. Calcium stones are the most common, seen in seventy to eighty percent of cases. This group is further divided, as stones may be calcium oxalate, which is more common, or calcium phosphate. Uric acid stones and struvite stones are seen in approximately ten percent of patients. Uric acid stones are caused by fluctuations in the body's chemical concentration, resulting in acidic urine. This type of kidney stone is often seen with frequent/severe dehydration. For this reason, patients experiencing conditions that cause chronic diarrhea, such as irritable bowel syndrome or Crohn's disease, will likely see this kind of stone. Type 2 diabetes mellitus and gout also have been linked to uric acid kidney stones. Further, a diet with a high intake of animal protein can decrease the body's pH, creating an acidic environment. Struvite, also known as infection stones, is caused by recurrent urinary tract infections (UTI). This occurs because the presence of gram-negative bacteria, such as E. coli, the most common bacteria to cause UTIs, increases pH and creates an alkaline environment. Magnesium ammonium phosphate, known as struvite, is formed into a stone when the urine is more alkaline. Struvite stones can be particularly harmful and painful, as they grow at a fast rate and often develop branches. The final and least common kidney stones are cystine stones. Cystine stones are associated with a genetic metabolic disorder of the kidneys called cystinuria. This condition is characterized by a decreased ability to reabsorb an amino acid, cystine, back into the kidneys, resulting in an increased concentration in the urine. It is estimated that less than three percent of kidney stones fall under this category, and it is often seen in childhood.