Mouse kidneys are located on the dorsal (upper) wall of the abdominal cavity and are securely held in place by fibrous capsules. Like other mammalian kidneys, the outer layer of the kidney is brownish red and granular in appearance, with a firm consistency. Mouse kidneys are similar to human kidneys, which is why they are often used to simulate human kidneys in scientific studies. Mice have played a significant role in experiments used to diagnose the possible cause and treatment of IgA nephropathy, or Berger's ("burrjays") disease. This is the most common non-diabetic kidney disease and affects as many as two to four percent of the world's population.