Purpura nephritis recovers quickly in the acute stage, for example, within a month, the child’s urine protein can go from excreting 5g per day to completely turning negative, and also from naked eye hematuria to only seeing red blood cells under the microscope. As a result, the child’s parents also go from anxious and fearful to happy and relaxed very quickly. However, during the recovery period, the child’s hematuria often lingers for a long time, fluctuating between 1+ and 3+. Why does occult blood last so long? Most cases of occult blood in the urine mean that the child has hematuria. In the disease purpura nephritis, hematuria means that there is a slight break in the glomerular filtration membrane, which allows the red blood cells in the blood to filter out. Due to the peculiarity of the glomerular filtration membrane structure, these tiny breaks are difficult to repair, so the recovery is especially slow, plus sometimes new damage to the kidney can occur due to excessive exercise, various infections, and allergies, therefore, during the recovery period, the hematuria of purpura nephritis will last for a long time, which can be up to 3~5 years.