Radical nephrectomy has been the standard treatment for kidney cancer. However, in cases where kidney cancer is present in only one kidney (i.e. isolated kidney), or both kidneys have kidney cancer, or although there are two kidneys, one kidney has a tumor and the other kidney has atrophied and is non-functional due to disease or other reasons (i.e. functional isolated kidney), in these cases if radical nephrectomy (i.e. standard treatment for kidney cancer) is performed, the patient will have no kidney or will have renal In these cases, if radical nephrectomy is performed (i.e., standard treatment for kidney cancer), the patient will have no kidney or will have renal insufficiency. We know that a person cannot live without a kidney or with a severely deficient kidney unless alternative therapies (such as hemodialysis or peritoneal dialysis) or a kidney transplant are used. Both dialysis and kidney transplantation are very expensive, not to mention their side effects or impact on quality of life. Therefore, whenever possible, these kidney cancer patients should undergo kidney-preserving surgery to remove the tumor while preserving functional normal kidney tissue. After years of clinical observation, it is found that patients with isolated or double kidney cancer have obtained good results after kidney preservation surgery, and the actual results are comparable to those of radical nephrectomy if compared by tumor stage, which provides strong evidence for kidney preservation surgery in other kidney cancer patients in the future. In medical terms, kidney-conserving surgery in these kidney cancer patients is called an absolute indication. Encouraged by these results, urologists have been very cautious in applying kidney-conserving surgery to patients with kidney cancer who have potentially function-threatening diseases (e.g., hypertension, diabetes, systemic lupus erythematosus, hyperuricemia, chronic nephritis or pyelonephritis, renal vascular disease, etc.) that may cause renal impairment in the near future after removal of a kidney despite the patient’s normal total renal function at the time of surgery. Although the total kidney function is normal at the time of surgery, the above-mentioned diseases may cause renal impairment and renal insufficiency or uremia in the near future after removal of one kidney. After long-term observation of a large number of cases, good tumor control has been achieved in these patients. The relative indications for kidney-conserving surgery in these kidney cancer patients are called kidney-conserving surgery. With the good results achieved in the above two types of kidney cancer patients, is it appropriate to perform kidney-conserving surgery when the kidney function is completely normal, there is no disease affecting kidney function, and the tumor is 4-5 cm in size? After the observation of a large number of clinical cases in the last 10-20 years, the effect of kidney preservation surgery is almost the same as that of radical nephrectomy. Many worries (such as tumor recurrence and metastasis) about kidney-conserving surgery for this kind of kidney cancer patients in the past have been dispelled in front of the facts. This is the third category of indications for kidney cancer preservation surgery, i.e. elective indications.