Focal nephrogenesis is caused by acute renal failure. Acute renal failure is a clinical syndrome in which the urinary function of the kidney is drastically reduced by the kidney itself or by extra-renal causes, resulting in a serious disturbance of the internal environment of the body. The main manifestations are oliguria or anuria, azotemia, hyperkalemia and metabolic acidosis. According to the different causes of acute renal failure and their respective pathophysiological characteristics, the etiology can be divided into pre-renal such as blood loss, shock, severe water loss, electrolyte balance disorders, acute circulatory failure, etc., renal such as acute glomerulonephritis, acute tubular necrosis, massive crush injury, etc.; post-renal such as complete urinary tract obstruction. Among them, acute tubular necrosis is the most common and characteristic, and the continued development of prerenal failure can also be transformed into acute tubular necrosis. Focal renal necrosis can also be seen in nasal malignant granuloma involving the kidney.