Renal cysts include solitary renal cysts, congenital polycystic kidney and congenital multiple renal cysts. The walls of these cysts are thin, the cysts are filled with clarified yellowish fluid, and most of the cysts are walnut-sized. Recently, the number of people with renal cysts has increased because of the wide availability of ultrasound examination. The main clinical symptoms of renal cysts Most of the renal cysts are asymptomatic. Some patients may have the following symptoms due to the cyst itself and the increased pressure inside the cyst, infection, etc.: ① Discomfort or pain in the waist and abdomen: it is caused by the enlargement and expansion of the kidney, which increases the tension of the kidney envelope and strains the kidney tissues, or puts pressure on the neighboring organs. In addition, polycystic kidneys cause the kidneys to contain a lot of water, become heavy and pull down, which also causes pain in the lower back. The pain is characterized by vague and dull pain, fixed on one or both sides, radiating to the lower part and low back. If there is intracapsular hemorrhage or secondary infection, the pain will suddenly increase. If there is a combined stone or a blood clot blocking the urinary tract after bleeding, renal colic may occur. ②Hematuria: It can be manifested as microscopic hematuria or meatus hematuria. The attacks are cyclic in nature. Back pain often increases during the attack, and can be triggered or aggravated by strenuous exercise, trauma, or infection. The reason for bleeding is because there are many arteries underneath the wall of the capsule. Due to increased pressure or combined infection, the blood vessels of the capsule wall rupture and bleed due to excessive strain. (③) Abdominal mass: Sometimes it is the main reason for patients to visit the clinic, and the enlarged kidney can be palpated in 60% to 80% of patients. Generally speaking, the larger the kidney, the worse the kidney function. ④Proteinuria: usually the amount is not much, not more than 2g in 24 hours urine. mostly no nephrotic syndrome will occur. ⑤ Hypertension: solid cyst compresses the kidney, causing renal ischemia, which increases renin secretion and causes hypertension. When the kidney function is normal, hypertension has occurred in more than 50% of patients, and the incidence of hypertension is higher when the kidney function is decreasing. (6) Renal hypofunction: due to cyst occupancy and compression, normal renal tissue is significantly reduced and renal function progressively decreases. Examination methods of renal cysts The more reliable methods are X-ray imaging, B-type ultrasonography of kidney, radionuclide scan and CT examination. In the case of renal cysts, urographic radiography may see distortion of the renal pelvis and calyces under pressure, but with smooth edges and no destruction. Renal cyst is not a tumor, but it is very easy to be confused with tumor, so it is important to differentiate renal cyst from renal malignant tumor. The method of differentiation between the two can be done by renal parenchymal tomography or renal arteriography. In renal parenchymal tomography, the image of cyst site is shallow, while the image of tumor site is deep; in renal arteriography, the cyst site is sparsely vascularized without contrast concentration, while renal malignant tumor is richly vascularized with contrast concentration. B-type ultrasound and CT can easily distinguish renal cysts from renal parenchymal tumors. Treatment methods of renal cysts The current medical level has no special method to treat renal cysts. For small renal cysts, no treatment is needed when there is no symptom, but regular review should be done to observe whether the cyst continues to increase in size. Asymptomatic people should have frequent urine examination, including urine routine and urine culture, and kidney function tests, including endogenous creatinine clearance, every six months to a year. Renal cyst puncture is not very useful, not only is it easy to be infected and recur, but also after long-term observation, the procedure cannot delay the onset of renal function damage. When the mass is large and has malignant potential, laparoscopic exploration can be performed, and if it is confirmed to be a benign cyst, the cystic wall on the surface of the kidney can be removed, and the edges are sutured continuously to the renal parenchyma with intestinal sutures, and the residual cystic wall is coated with tincture of iodine. In case of extensive destruction of renal parenchyma on one side and normal renal function on the opposite side, laparoscopic nephrectomy is feasible. Laparoscopic treatment is a good minimally invasive surgical method nowadays.