How can severe blood loss or shock lead to acute renal failure?

Severe blood loss or shock can lead to acute renal failure primarily through the mechanism of ischemia, or a poor supply of blood to the kidneys.1

When cardiac output is lowered by hemorrhage or medical or surgical shock, the body’s systemic blood pressure drops significantly. This causes the renal circulation to be depressed even more severely than the rest of the body's circulation. This reduction in blood flow leads to two major consequences:12

• Inefficient Excretion: The immediate drop in renal blood flow can cause a temporary cessation of urine formation, as the kidneys cannot maintain the necessary glomerular function to filter the blood.12
• Tissue Damage: If the impairment of the blood supply is prolonged, the kidney tissue cannot survive the lack of oxygen and nutrients. This leads to necrosis (tissue death), which may be patchy or massive.1

While this damage is severe, it is potentially reversible if the underlying circulatory failure is treated promptly—for example, through the transfusion of blood or fluids—allowing the kidney tissue time to regenerate.1