Kidney-the kidney, the main excretory organ of human beings or animals, is on both sides of the lumbar vertebrae. Because the right side has a substantial organ, the liver occupies space, most people's left kidney is slightly higher than the right kidney. It is a dark red solid organ, shaped like a broad bean. The surface of kidney is smooth, which can be divided into upper and lower ends, front and back sides, and inner and outer edges.