Ischemic nephropathy: noninvasive testing

Ischemic nephropathy is defined as hypertension and a defect in renal function and/or loss of renal parenchyma caused by hemodynamic changes secondary to a renal artery stenosis. A work-up should be reserved for those patients considered candidates for intervention with percutaneous transluminal renal angioplasty (PTRA) or reconstructive surgery in whom there is hypertension with clinical features suggestive of ischemic nephropathy and/or a significant size disparity between the kidneys. Therefore, all patients suspected of ischemic nephropathy should undergo a renal ultrasound examination to quantitate renal size and a test of overall renal function (creatinine clearance or DTPA plasma disappearance). The diagnostic accuracy of functional tests for renovascular hypertension can be seriously impaired in the presence of renal insufficiency, and they have not been evaluated systematically in this clinical setting. Therefore, tests are reserved for those patients in whom the clinical clues of ischemic nephropathy are equivocal. Available evidence suggests that angiotensin-converting enzyme inhibitor (ACEI)-induced changes in the Hippuran or Mag3 renogram are predictive of reversible renovascular hypertension in the presence of renal insufficiency. Duplex ultrasound scanning of the renal arteries is an accurate method to identify renal artery stenosis in experienced hands. However, there is no quantitative information to judge the utility of noninvasive tests in predicting which patients with ischemic nephropathy will have an improvement in renal function after intervention.