Kidney damaged by tuberculosis. Sectioned gross specimen of a kidney in a case of tuberculosis of the kidney (renal tuberculosis). Tuberculosis (TB) is caused by Mycobacterium tuberculosis bacteria. They usually affect the lungs, but can travel to other organs, such as the kidneys, in the blood. The bacteria form tubercles in the medulla and tubules of the kidney, which may join to form necrotic cavities with fibrotic and scar tissue. Eventually the kidney starts to fail. This kidney has an pale, unhealthy colour. A normal kidney has a dark red-brown colour. One possible treatment for kidney failure is a kidney transplant.