Renal enlargement due to renal parenchymal disease: mainly seen in acute glomerulonephritis and acute progressive nephritis. As the enlarged kidney involves the renal envelope, there will be local persistent swelling and dull pain. Some patients also have carnal hematuria, swelling and hypertension. It can be diagnosed by laboratory urine test. Infectious diseases of the kidney: such as renal abscess and acute pyelonephritis, which mainly originate from bacterial infection. It is mostly unilateral lumbar pain, difficult to tolerate pressure and percussion examination, often accompanied by fever and chills. It can be diagnosed by laboratory blood and urine tests and ultrasound. Kidney tumors or cysts: such as renal cysts, polycystic kidneys, benign and malignant tumors, etc. If the cyst or tumor is large enough to involve the kidney envelope, it will cause persistent distension and dull pain. The diagnosis can be confirmed by ultrasound or CT. Kidney stone: If the stone is embedded in the ureter, renal colic will occur, which is intermittent, episodic and severe, and may radiate to the perineum. In severe cases, it may be accompanied by profuse sweating and nausea and vomiting, as well as the appearance of hematuria in the naked eye. Whether the back pain is caused by kidney disease can be initially determined by routine urinalysis and ultrasound, and if necessary, additional ultrasound or abdominal X-ray can be done to confirm the diagnosis.