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Genitourinary tract imaging - part 3

Chụp động mạch thận là xét nghiệm giải phẫu của Chính xác NHẤT để chẩn đoán của RAS, nó sử dụng các tác nhân tương phản mục tiêu có khả năng độc thận và liều bức xạ liên quan của nó là cao so với các điều khoản khác. CT chụp mạch (CTA), cộng hưởng từ (MRA) và siêu âm Doppler (DS) là phương pháp tiếp cận mới | Nuclear Imaging in the Genitourinary Tract 31 Fig. 2. Renal study with MAG3 in a patient who had suspected obstruction of the right kidney. The upper row of images demonstrates rapid clearance of tracer from a small left kidney but delayed clearance from the normalsized right kidney. The time-activity curves demonstrate a marked acceleration of clearance after furosemide administration in the left kidney. In contrast the drug effect is blunted significantly in the right kidney consistent with partial obstruction. Other imaging modalities Renal angiography is the most accurate test for anatomic diagnosis of RAS but it uses potentially nephrotoxic contrast agents and its associated radiation dose is high compared with other modalities. CT angiography CTA magnetic resonance angiography MRA and Doppler sonography DS are new noninvasive approaches for the diagnosis of renal artery stenosis. DS can be used to monitor recurrent stenosis after corrective therapy and is effective for classifying patients as responders or nonresponders to therapy. Unfortunately US criteria for RAS based on evaluation of renal peak systolic velocity and renal aortic ratio are controversial. CTA and MRA provide anatomic information about renal artery stenosis. CTA has higher spatial resolution than MRA and can be used to evaluate the calcium content of atherosclerotic lesions before treatment however the associated radiation dose is high and potentially nephrotoxic contrast agents are required. In contrast MRA does not expose patients to ionizing radiation or directly nephrotoxic contrast agents. Recently Eklof and colleagues 92 compared DS MRA CTA DS and captopril renography for assessing renal artery disease and concluded that MRA and CTA were significantly better than duplex US and captopril renography for detecting hemodynamically significant RAS. A metaanalysis performed by Vasbinder and colleagues 93 supports these findings. Future prospects Although captopril renography can play an .