The researchers studied how ultrasound measurements of the kidney cortex can show changes during acute kidney failure in rabbits. They injected glycerin into the rabbits to induce kidney failure and used ultrasound to measure the kidney tissue. They found that the ultrasound readings of the kidney cortex increased significantly during kidney failure, while the readings of the kidney medulla did not change much. The kidney cortex showed signs of damage like tubule blockages, cell swelling, and tissue swelling. The increase in ultrasound readings of the kidney cortex was linked to these kidney damage signs.