A parapelvic cyst is a benign cyst originating from the renal hilum at the renal parenchyma and does not communicate with the collecting system. The etiology is lytic dilatation, probably due to chronic inflammation. It is mainly associated with compression of the renal collecting system or renal tip artery and complications caused by the cyst, manifested by symptoms such as back pain, hypertension, hematuria and urinary tract infection, and the presence or absence of symptoms is highly correlated with the location and size of the cyst and its complications. The initial diagnosis of this disease depends on imaging examination, CT examination is most definitely useful in the diagnosis of this disease, IVP examination also has a high accuracy rate in the diagnosis of this disease, it can understand the bilateral renal function, the morphology of the renal collecting system and complications, it is easy to suggest the occupying lesion at the renal hilum and should be used as a routine examination. ultrasound in the diagnosis of this disease is sometimes easily misdiagnosed as hydronephrosis, in ultrasound examination suggests unexplained CT scan shows that the cyst is located at the renal hilum, separated from the normal renal parenchyma, and the lowest density halo around the cyst is the characteristic manifestation of parapelvic cyst, and the CT scan of parapelvic cyst can be similar to hydronephrosis, but there is no enhancement on the enhanced scan, and the contrasted renal pelvis and calyces are compressed and elongated, which can set off the cyst more clearly. The diagnosis of parapelvic cyst is clear based on the above history and ancillary tests. The differential diagnosis of parapelvic cyst is as follows: 1. Hydronephrosis: hydronephrosis can be caused by multiple factors within and outside the urinary system, congenital and acquired, and can occur in all age groups. Patients mostly have no obvious clinical symptoms, and when hydrocele is serious, there can be a feeling of swelling in the waist and abdominal mass. Patients with intermittent hydronephrosis caused by stones may develop renal colic with nausea, vomiting, abdominal distention and scanty urination. In severe cases of hydronephrosis, enlarged kidneys may be palpable on examination, and in case of co-infection, pus urine and systemic infection symptoms may appear. Diagnosis mainly relies on ultrasound, IVP, CT and MRI, etc. 2.Renal tumor: It is a common tumor in the urinary system, divided into benign and malignant, benign tumor is rare. Benign tumors mostly have no typical clinical symptoms, but when they are larger, they may cause pain and discomfort in the lower back and abdomen, and the enlarged kidney can be palpated on body examination. The typical clinical manifestations of malignant tumors in kidney are hematuria, lumbar pain and mass. The diagnosis mainly relies on ultrasound, enhanced CT and MRI, etc. It mostly presents as solid occupying lesions, each with cystic solid features. Parapelvic cysts can be followed up regularly because they are benign lesions with small and asymptomatic cysts, but when the cysts are >5 cm in diameter, or when pressure symptoms and complications appear, surgery should be actively taken. Surgical methods include open cyst decompression, B-ultrasound guided puncture aspiration of intracapsular fluid for injection of sclerosing agent and laparoscopic cystectomy. Because of the complex structure of renal portal and deep cyst, puncture and aspiration of intracapsular fluid for injection of sclerosing agent is very easy to cause complications and high recurrence rate, so it is not suitable. Traditional open surgery requires a large incision in the lumbar region, which causes great damage to the body, slow postoperative recovery and long hospital stay. Laparoscopy is worth promoting in the clinic because of multi-angle observation and magnification, adequate intraoperative exposure, good hemostasis, and minimally invasive. Histologically parapelvic cysts are divided into two types: urogenic and nonuricogenic, the latter being subdivided into plasmacytotic and lymphatic. Most parapelvic cysts are caused by congenital factors, but most patients develop parapelvic cysts after the age of 50 years and often have a previous history of urinary tract infection, obstruction or stones. They may be caused by chronic inflammation and obstruction of the pelvic lymphatics, resulting in local lymphatic dilation, and local vascular disease or vascular disuse atrophy of the renal sinus, which may also cause plasma to leak out into the plane of the renal sinus and become confined there and form plasmacytic cysts. Urogenic cysts may be formed by the extension of cysts in the renal parenchyma to the hilum. It is most commonly seen in patients over 50 years of age. Asymptomatic parapelvic cysts are seen in a similar proportion of men and women, while those with clinical symptoms are more common in men. Clinical manifestations may include lumbar pain and discomfort, hematuria, hypertension, or intracapsular stones, while some patients are asymptomatic and are found incidentally during physical examination. The diagnosis can be made on the basis of ultrasound, IVU and CT examination, which can reveal a dark area of fluid near the renal hilum and show the size of the cyst, but when the cyst extends into the renal sinus and causes fluid in the pelvis and calyces, or when the cyst is located deep in the renal sinus, it can be misdiagnosed as pyelonephritis. CT examination is the most reliable diagnostic method, which can show a well-defined uniform low-density oval mass next to the renal pelvis with CT values of 0-20 HU and little change in CT values before and after enhancement, which can be diagnosed as a benign cyst next to the renal pelvis; parapelvic cysts are located in the renal sinus, and larger cysts can protrude towards the hilum Ultrasound and CT examination can help in differential diagnosis. In addition, CT examination also has important diagnostic value to identify cystic kidney cancer. Small cysts without symptoms can be reviewed by ultrasound regularly and followed up closely. For larger cysts, local compression of the pelvis and calyces with clinical symptoms, or intracapsular stones and other lesions of the affected kidney such as malformation tumor, surgery is recommended. The traditional surgical approach is to remove most of the cyst wall, destroy the remaining cystic epithelium with anhydrous alcohol, and fill in the tipped fat around the renal pelvis. Intraoperative attention should be paid to whether the cystic cavity has traffic with the renal pelvis and calyces, especially in patients with intracapsular combined stones. Ultrasound-guided aspiration of the cystic fluid by puncture has been reported to cure parapelvic cysts. This method may be a better treatment for simple parapelvic cysts, but because parapelvic cysts are adjacent to the blood vessels of the renal hilum, the operator should be skilled in puncturing renal cysts to prevent serious complications. Laparoscopic surgery for parapelvic cysts requires a high level of operator skill, and we should pay attention to the following points: 1. Preoperatively, the location, size, number of cysts and the relationship with the surrounding vessels and renal collecting system should be clarified; 2. Since parapelvic cysts are close to the renal hilum, care should be taken when separating parapelvic cysts; the walls of renal veins and inferior vena cava are dark blue under laparoscopy, which are similar to the top of the cysts, so care should be taken to identify them and operate carefully to avoid If the cyst is indistinguishable from the dilated renal pelvis, the renal pelvis can be squeezed, and the pelvis will become empty, while the cyst will not change; secondly, a cystoscopic retrograde ureteral catheter can be inserted as a guideline before surgery, and a US blue can be injected intraoperatively to identify the cyst and the renal pelvis and whether there is a pelvic incision; then the cyst can be confirmed by laparoscopic guideline puncture and extraction of yellowish fluid; 4. 5. If the anatomical view is unclear, variation, or hemorrhage is encountered, the patient should be referred for open surgery in a timely manner; 6. Filling the renal portal with fat in the parapelvic cyst can further prevent postoperative recurrence; 7. . Laparoscopic technology for the treatment of parapelvic cysts is safe and reliable, fully reflecting the minimally invasive advantages of laparoscopic surgery. With the increasing popularity and development of laparoscopic technology, laparoscopic cyst debulking will definitely become the preferred method for the treatment of parapelvic cysts.