Objective To report a case of missed diagnosis of small renal carcinoma by ultrasonography, and to explore the diagnosis methods and the causes of misdiagnosis and missed diagnosis of small renal carcinoma by ultrasonography through literature review.Methods The diagnosis and treatment process of 1 case of small renal carcinoma missed by ultrasonography was reported, the relevant domestic literatures from Jan. 1, 1995 to Aug. 30, 2020 were reviewed, and the ultrasound diagnosis methods and the causes of missed diagnosis and misdiagnosis of small renal carcinoma were summarized.Results The right renal space occupying of the patient was missed in the first ultrasound examination, and only the left renal space occupying was detected. Without any change of the examination equipment, only with improved examination conditions, the ultrasound reexamination still failed to detect the right renal space occupying. After replacing the ultrasound equipment with higher imaging quality ones for 2 consecutive times and with improved examination conditions, the case was diagnosed as bilateral renal space occupying, with a high probability of malignancy. Postoperative pathology confirmed renal clear cell carcinoma in both renal masses. A total of 37 literatures related to ultrasound diagnosis of small renal carcinoma were retrieved, including 1 611 cases. The ultrasound echo types of small renal carcinoma were mainly hyperechoic (39.4%[329/836]) and hypoechoic (39.0%[326/836]). The dendritic blood flow signal in the parenchyma (44.7%[220/492]) was the most visible color Doppler flow signal in small renal carcinoma. Small renal carcinoma had the characteristic of "fast in and fast out" by contrast-enhanced ultrasound, and there were significant differences in contrast-enhanced ultrasound of different pathological types of small renal carcinoma (χ_c²=37.58, P=0.01). The sensitivity of conventional ultrasound in the diagnosis of small renal carcinoma was not significantly different from that of contrast-enhanced ultrasound, plain CT+enhanced CT or plain MRI+enhanced MRI (χ²=0.30, P=0.96). The misdiagnosis rate and missed diagnosis rate of small renal carcinoma by conventional ultrasound were 15.3% (139/908) and 1.8% (17/919), respectively. Renal hamartoma was the most common misdiagnosis disease (47.3%[52/110]). The factors of missed diagnosis mainly included the image quality of ultrasound equipment, the relative position of small renal carcinoma, the factors of the operator and the patients' conditions.Conclusion The echo type, blood flow, filling of contrast agent and regression speed of small renal carcinoma show different characteristics. The quality of ultrasound equipment may affect the screening of small renal carcinoma. Ultrasound physicians who fully understand the performance of the equipment and fully understand the clinical, imaging and pathological characteristics of patients, are helpful to improve the diagnosis accuracy of small renal carcinoma.