Retroperitoneal bronchogenic cyst is rare clinically. In September 2006, a case was admitted to our hospital and laparoscopic resection of retroperitoneal mass was performed with satisfactory results, which is reported below. The patient, male, 41 years old. He was admitted to the hospital because of intermittent left-sided lumbar abdominal pain and discomfort for 1 month, which was aggravated for 10 d. The pain was prominent in the right-sided lying position and during inspiration, occasionally accompanied by nausea and erratic. On examination, a round suspicious mass with a diameter of about 5 cm, soft, slightly mobile and with deep pressure pain could be found under the ribs of the left upper abdomen. Ultrasound showed a hypoechoic mass in the left epigastrium, which was considered to be from the retroperitoneal adrenal gland, and KUB+IVU showed that the left kidney was displaced inferiorly by compression. MRI showed a class of round cystic slightly long T1 and long T2 signal foci above the left kidney and medial to the spleen, with short T1 signal liquid flat at the bottom and low signal fat suppression sequence, and a small amount of irregular low signal separation within the capsule, with abnormal signal foci of about 5.3cm×8.2cm×8.0cm in size, with thin and uniform walls and smooth edges, and mild wall enhancement after enhancement. The left adrenal gland was compressed and partially visible medially. The preoperative diagnosis was a left retroperitoneal cystic mass, the nature of which was to be determined. Intraoperative exploration revealed a subcircular mass of about 7 cm × 6 cm × 5 cm in the supra-adrenal region of the left kidney, with an intact envelope and smooth surface, reaching the diaphragm at the upper pole and the spleen laterally, compressing the left kidney inferiorly and adhering closely to the left adrenal gland medially. The cyst ruptured during the separation process, and a viscous yellowish turbid fluid with a volume of about 220 ml was spilled from the cyst. the mass and the adrenal gland were removed after aspiration, and the retroperitoneal space was flushed with colestipol injection. Postoperative pathological examination: the gross specimen showed a dark red cystic mass in the left adrenal gland with a broken wall, smooth surface and rough inner surface, reticulated and distributed with small cystic cavities, no obvious hair, teeth, bones and grease-like material were found inside the cyst. Microscopically, the cyst wall was found to be lined with pseudo-complex ciliated columnar epithelium, in addition to smooth muscle fibers, bronchial lymphatic tissue and secretory glands, etc. No obvious tumor cells were seen. The cyst was considered as retroperitoneal bronchogenic cyst according to the pathological diagnosis. The culture result of the cyst fluid was Staphylococcus epidermidis. After surgery, the patient recovered well, his symptoms disappeared, and he was discharged 9 d after surgery. The follow-up was 6 months, and no recurrence or metastasis of the mass was found on repeat ultrasound and CT. Discussion Bronchogenic cysts are a relatively rare group of developmental abnormalities that often occur in the mediastinum and occasionally in other parts of the body, such as skin and subcutaneous tissue, anterior sternal tissue, pericardium, vertebral canal and diaphragm, and only rarely are they located completely in the abdominal cavity, and more rarely in the retroperitoneum. Retroperitoneal bronchogenic cysts can occur at any age and there is no significant difference in the prevalence between men and women. The cysts are benign masses, mostly located in the left adrenal region, and rarely in the kidneys, spleen and around the pancreas. It usually has no obvious clinical symptoms and can be detected incidentally during physical examination. When the cyst enlarges causing local compression or secondary infection, it may cause symptoms such as epigastric discomfort, nausea and vomiting, lumbar pain and fever. Abdominal ultrasound, CT and MRI are better examinations to detect retroperitoneal masses and their sizes, but it is not easy to clarify the nature of the masses, and preoperative attention should be paid to differentiate them from cystic teratoma, adrenal cyst, pancreatic cyst and uroepithelial cyst. Pathological examination is the main method to confirm the diagnosis of bronchogenic cysts, and the cyst wall lined with pseudo-complex ciliated columnar epithelium can be found microscopically. Surgery is the first choice for the management of this disease, and there are reports in the literature that the application of laparoscopy to remove the mass has greater advantages in terms of ease of operation, minimal surgical trauma, rapid postoperative recovery, and significant improvement in symptoms, with satisfactory results. Retroperitoneal bronchogenic cysts have a good prognosis if treated promptly and reasonably, and only a small proportion of cysts have the potential for malignancy. References 1. Chen YD, Liu HR. A case of retroperitoneal bronchogenic cyst. Chinese Journal of Pathology, 1997, 26: 206. 2. Itoh H, Shitamura T, Kataoka H, et al. Retroperitoneal bronchogenic cyst: Report of a case and literature review. Pathol Int, 1999, 49, 152-155. 1999, 49, 152-155. 3. Ishikawa, T, Kawabata G, Okada H, et al. Retroperitoneal bronchogenic cyst managed with retroperitoneoscopic surgery. Ishizuka O, Misawa K, Nakazawa M, et al. 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