Methods for Detection of Renal Artery Obstructions
| Method | Strength | Limitation |
|---|---|---|
| Doppler sonography (±captopril enhancement) (58) | Is reasonably expensive and widely available | Is operator dependent (more reliable in centers with dedicated radiologists) |
| Measures renal length | Has high rate of unsuccessful studies (10%–20% due to obesity or bowel gas) | |
| Can monitor recurrent stenosis after corrective therapy | Is less useful than MRI or CT angiography for diagnosing abnormalities in FMD or accessory renal arteries | |
| Is effective in classifying patients as responders or nonresponders to therapy (renal resistance index ≥ 80%) | ||
| MRA (59) | Does not expose patient to ionizing radiation or nephrotoxic contrast agents | Poorly reveals distal segments and small accessory renal arteries |
| Is useful in patients with renal failure | Is affected by respiratory artifacts, intestinal peristalsis, stents, or claustrophobia in the patient | |
| Has high negative predictive value (98%) | Is costly and of limited availability | |
| Seems best diagnostic tool for atherosclerotic RAS | Has low positive predictive value even in selected population | |
| MRI (±captopril enhancement) (60) | Does not expose patient to ionizing radiation | Has same advantages as MRA |
| May allow identification of responders to percutaneous renal angioplasty | ||
| CT angiography (59) | Has higher spatial resolution than that of MRA | Uses nephrotoxic contrast agent and high radiation dose |
| Shows calcium content of atherosclerotic lesions before treatment | Poorly reveals distal segments and small accessory renal arteries | |
| Does not have artifacts caused by stents | ||
| CT (58) | Measures cortical thickness and renal length, which are decreased in unilateral RAS | Uses nephrotoxic contrast agent and high radiation dose |
| Is not yet fully developed | ||
| Captopril-enhanced renography (61) | Is reasonably expensive; safe | Is less accurate in cases of renal function impairment, bilateral stenosis, or unilateral stenosis in a patient with only 1 kidney |
| Identifies patients whose blood pressure will improve after RAS correction | ||
| Excludes RVH if findings are normal | ||
| Renal angiography (62) | Is most accurate test for anatomic RAS (gold standard) | Uses nephrotoxic contrast agent and high radiation dose |
| Allows use of less contrast agent with digital subtraction angiography | Can be affected by interobserver variability |