Why are kidneys brown?

Kidneys appear brown due to their rich vascularization and the presence of various pigments, including hemoglobin from the blood supply. The brown color is primarily a result of the high concentration of iron in hemoglobin and the accumulation of certain metabolites and waste products. Additionally, the renal cortex and medulla contain different types of tissues that contribute to the overall coloration. This brown hue is normal and reflects the organ's function in filtering blood and producing urine.