Objective To analyze the characteristics of conventional ultrasound and contrast-enhanced ultrasound(CEUS)in hypovascular renal tumors,and to explore the application value of combining the 2 methods in diagnosing benign and malignant hypovascular renal tumors.Methods The conventional ultrasound and CEUS data of 104 hypovascular renal tumors(76 benign lesions[benign group]and 28 malignant lesions[malignant group])from 99 patients,who were confirmed by postoperative pathology,biopsy pathology or computed tomography(CT)/magnetic resonance imaging(MRI)enhancement combined with long-term follow-up in Ruijin Hospital,Shanghai Jiao Tong University School of Medicine and its Wuxi Branch from Oct.13,2009 to Oct.26,2022,were retrospectively analyzed.The location,size,internal echo,morphology,internal and peripheral blood supply of the lesions were observed by conventional ultrasound,and the perfusion mode,regression pattern,perfusion uniformity and ring enhancement signs were observed by CEUS.Taking the pathological results or confirmed results of CT/MRI enhancement combined with long-term follow-up as the gold standard,the value of conventional ultrasound combined with CEUS in the differential diagnosis of benign and malignant hypovascular renal tumors was analyzed.Results There were significant differences in gender,age of patients and internal echo,contrast agent regression and ring enhancement signs of lesions between the 2 groups(all P＜0.05).The malignant tumors were mostly found in males(78.6％,22/28)with an average age of(58.29±11.76)years old;the masses were mostly hypoechoic(64.3％,18/28),and rapid washout was predominant with CEUS(60.7％,17/28).In the benign group,most of the patients were female(55.3％,42/76),with an average age of(50.64±14.88)years old;the majority of the masses were hyperechoic(64.5％,49/76),and CEUS showed simultaneous washout as the main lesion(56.6％,43/76).Three patients(10.7％,3/28)with ring enhancement signs were all malignant.The diagnostic accuracy(82.7％)and specificity(88.2％)for benign and malignant hypovascular renal tumors were relatively high when combining the diagnostic indicators of ring enhancement signs and hypoechoic.The diagnostic sensitivity(85.7％)and negative predictive value(92.3％)were relatively high when combining the 3 diagnostic indicators of ring enhancement,hypoechoic,and rapid washout.Conclusion Conventional ultrasound combined with CEUS has significant clinical practical value in the differential diagnosis of benign and malignant hypovascular renal tumors.The ring enhancement sign is highly specific in the diagnosis of malignant hypovascular renal tumors.However,if this sign is not significant and conventional ultrasound shows hypoechoic or CEUS exhibits rapid washout,there is a strong suggestion that the mass may be a malignant lesion.