It all depends on the disease process leading to increased blood urea&serum creatinine. This may be due to acute conditions(short duration disease like acute infection, obstruction, drug reaction) Or chronic(long term) like due to chronic infection,diabetes,hypertension,chronic  kidney parenchymal diseases.chronic obstruction. Treatment or control of the cause or the disease is the treatment of renal failure. Dialysis is only a  supportive means to decrease blood urea /creatinine and other harmful nitrogenous waste products by a machine.which lessons the harmful effects of raised nitrogenous waste products .