Different organs receive different amounts of cardiac output. The organ with MAXIMUM blood flow in ml/kg/min is:

The kidneys receive 20-25% of the cardiac output. They receive the highest blood flow per gram of organ weight in the body i.e, 400 mL/min/ 100 gm. This is several times greater per unit weight of organ than the blood flow through most other organs. Ref: Radiological Imaging of the Kidney edited by Emilio Quaia, 2011, Page 24.