Results of ultrasonography depend on the amount of stroma and the size of the loculi (see the images below).
The appearance of multilocular cystic renal tumor includes multiple anechoic spaces separated by hyperechoic septa. This pattern is similar to that of multilocular cystic nephroma; however, if the loculi are small, the tumor mimics an echogenic solid mass.
In most patients, the renal origin of the mass can be confirmed by identifying a beak or claw of normal renal parenchyma around the periphery of a well-defined mass, by the splaying or displacement of the renal collecting system, and by synchronous motion of the mass and kidney with respiratory excursion.
Color Doppler US can also be used to evaluate tumors and can provide a noninvasive assessment of lesion vascularity. This is possible because of the Doppler-shifted signals of abnormally high velocity emitted by low-resistance neovascularity in some neoplasms.
Degree of confidence
US can be used with a high degree of confidence. A diagnosis can be made with high precision because sonograms clearly depict the structure of the lesions. False-positive and false-negative rates are low because of the accuracy of the method.
Limitations of techniques
The precision and accuracy of US depends on, and therefore is limited by, the operator's skill. CT may not be chosen if the patient has a severe allergy to the contrast medium. Compared with US and fast CT, MRI is limited by the need for sedation in some patients.
Objective: To explore the value of ultrasound in diagnosis of cystic renal cell carcinomas. Methods: Ultrasonic features in 27 cases including 29 focus with surgically and pathologically proved cystic renal cell carcinoma were analyzed. Results: According to the number of their capsular spaces, cystic renal carcinomas were classified into two patterns:single-cystic renal cell carcinoma and multi-cystic renal cell carcinoma. In our cases, compared with single-cystic renal cell carcinoma, the long diameter of multi-cystic renal cell carcinoma were enlarged (P=0.03, <0.05). Among ultrasonic findings of cystic renal cell carcinomas, 14 cases with 15 focus had irregular thickening cystic wall and/or septum, among which 1 case with diffuse calcification on thickening cystic wall and septum. The cystic wall were regular in 2 cases which were misdiagnosed as cyst of kidney, and the septum was regular in 1 case which was misdiagnosed as multilocular cyst of kidney. 10 cases with 11 focus had nodules on the cystic wall and/or septum and only one case had cystic change in nodule on the cystic wall. There were 14 cases with limous capsular space which showed meticulous and punctiform weak echo or inhomogeneous and hyperechoic sludged blood. The signal of arterial blood flow could be found in thickening cystic wall and septum and solid nodules by color Doppler ultrasonography. Maximum velocity (Vmax) and resistence index (RI) were without significant in feeding artery of single-cystic renal cell carcinoma and multi-cystic renal cell carcinoma (P=0.39, 0.36, >0.05). Pulse Doppler showed there were no significantly different in Vmax and RI between feeding artery of focus and normal interlobar artery of kidney (P=0.25, 0.27, > 0.05). Conclusions: Ultrasonography plays an important role in the diagnosis, differential diagnosis and early therapy of cystic renal cell carcinoma.