The sympathetic nervous system (SNS) and the renin–angiotensin-aldosterone system (RAAS) are overactive as a result of severe HCC, which also causes vasoconstriction, structural damage to the kidney, intravascular hypovolemia, necrosis, and apoptosis of tubular cells, which ultimately results in a complete decline in the GFR [22, 23]. The gene discussed is REN; the disease is hepatocellular carcinoma.