Differential diagnosis of renal lesions with US-angiography using intra-arterial CO2 microbubbles

To differentiate renal masses, 58 patients with renal masses (39 men and 19 women, aged 23-81 years [mean age 60 years]) underwent US-angiography with intra-arterial infusion of carbon dioxide (CO2) microbubbles during conventional angiography; 32 patients had renal cell carcinomas; nine, transitional cell carcinomas; nine, renal complicated cysts; four, angiomyolipomas; two, acute focal bacterial nephritis and hematomas. Renal masses were classified into six enhancement patterns of US-angiography. Thirty-one (97%) renal cell carcinomas were histologically alveolar type and demonstrated the well-enhancement pattern. All nine renal complicated cysts showed the non-enhancement pattern. Although transitional cell carcinomas did not show definite neovascularity on conventional angiography, they were classified as the well-enhancement pattern in 4/9 (44%) and poor-enhancement pattern in 5/9 (56%) on US-angiography. Four angiomyolipomas were homogeneously enhanced. Complicated cysts were clearly differentiated from renal cell carcinomas by the enhancement pattern on US-angiography. But the differentiation between renal cell carcinomas and angiomyolipomas was difficult. US-angiography is useful for detecting fine neovascularity of renal lesions and also for the differentiation or renal cell carcinomas from complicated cysts or transitional cell carcinomas during conventional angiography.