Abstract: Objective:To investigate the causes and value of ultrasonography for perirenal effusion． Methods: The causes and ultrasound features of 43 cases with perirenal effusion were retrospectively analyzed． Results:Among the 43 cases，acute urinary tract obstruction in 19 cases，acute pancreatitis in 8 cases，renal trauma in 6 cases，acute pyelonephritis in 5 cases，retroperitoneal hematoma in 4 cases and liver trauma in 1 case were found． The ultrasound feature of renal subcapsular effusion was crescent liquid dark area between renal capsule and renal parenchyma． The thickening adipose capsule was the manifestation of renal subcapsular effusion，and the liquid dark area in perirenal space was various multichip form． Conclusions:The ultrasound detection rate of perirenal effusion is high． Ultrasound can effectively find the primary lesions，dynamically observe the patient's condition and perirenal effusion absorption， which has high application value．