To explore missed diagnosis and misdiagnosis of small renal carcinoma and urothelial carcinoma. Methods The sonography features of 11 cases of small renal carcinoma and 7 cases of urothelial carcinoma were analyzed retrospectively.Results the type of misdiagnosis cases were as follow: there were 2 cases of angiomyolipoma of kidney which were hyper-echoic and 1 case showed internal and peripheral blood signal; 4 cases of renal cyst which were cystic of 3 cases; 5cases missed diagnosis in 11 cases of small renal carcinoma. There were 1 case of blood clot, 1case of parapelvic cyst, 5 cases missed diagnosis in 7cases of urothelial carcinoma. Conclusions Ultrasonography has high diagnostic value in small renal carcinoma, but still has some limitations, and sonographers lack awareness of urothelial carcinoma. we should combine with various imaging technique, to reduce rate of missed diagnosis and misdiagnosis.