Most cancers are named after the part of the body where the cancer first starts. Kidney cancer begins in the kidneys, 2 large, bean-shaped organs. One is just to the left and the other to the right of the backbone. The lower rib cage protects the kidneys. The kidneys filter the blood and help the body get rid of excess water, salt, and waste products in the form of urine. Urine travels through long tubes (ureters) to the bladder where it is stored until the person passes the urine, or urinates. Although we have two kidneys, it is possible to survive with less than even 1 complete kidney. Some people live without any working kidneys at all. Their blood is filtered by a machine in a process called dialysis. Like all cancers, kidney cancer begins small and grows larger over time. It usually grows as a single mass within the kidney. But a kidney can have more than one tumor. Sometimes tumors are found in both kidneys at the same time. The cancer might be found only after it has become quite large. Most of the time it is found before it has spread to other organs through the bloodstream.