Renal Physiology and Pathophysiology
Renovascular Hypertension and Ischemic Nephropathy
Frederick A. Gulmi; Ira W. Reiser; Samuel Spitalewitz
- A 67-year-old male with stable renal function and a creatinine of approximately 3 mg/dL presents with peripheral vascular disease and a blood pressure of 160/70 mm Hg. He was a long-standing smoker but has recently stopped. He is referred for evaluation for treatment of "ischemic nephropathy." He has hyperlipidemia and had a myocardial infarction 3 years before presentation. His current medications are a calcium channel blocker, an adequate-dose diuretic, and a statin. Which of the following is the most appropriate next step?
- Refer the patient for magnetic resonance angiography (MRA) with gadolinium.
- Add an angiotensin-converting enzyme (ACE) inhibitor.
- Refer for an angiogram.
- Increase the diuretic.
- Observe for deterioration in renal function and then refer for an angiogram.
- Which of the following is most similar to human renal vascular hypertension and is felt to be angiotensin dependent rather than volume dependent?
- The two-kidney, one-clip Goldblatt model
- The one-kidney, one-clip Goldblatt model
- The two-kidney, two-clip Goldblatt model
- Since the results of the Coral trial have been published, which statement is true regarding progression to end-stage renal disease?
- Surgical intervention and/or percutaneous angioplasty with intervention is no longer ever indicated.
- Medical intervention is superior to surgical intervention
- Medical intervention is superior to percutaneous angioplasty with stenting.
- Medical intervention is equal to percutaneous angioplasty with stenting.
- Percutaneous angioplasty with stenting is superior to medical intervention.
- Which of the following statements is TRUE regarding surgical revascularization of a renal artery?
- A kidney less than 8 cm in length can be successfully revascularized.
- Retrograde filling of the distal renal artery by collateral circulation on radiographic or scintigraphic imaging studies is more likely to result in a successful surgical outcome.
- Patients who require renal vascular surgery do not have significant vascular disease elsewhere.
- Correction of a renal artery lesion and an aortic aneurysm need to be done simultaneously.
- A renal ostial lesion always requires surgical revascularization rather than percutaneous angioplasty and stenting.
- Ischemic nephropathy results from:
- a reduction in renal blood flow and perfusion.
- proinflammatory cytokines and/or angiotensin II.
- an irreversible change in perfusion pressure.
- a failure of autoregulation alone.
- failure of development of collateral circulation.
- b. Add an angiotensin-converting enzyme (ACE) inhibitor.According to the Coral trial, medical therapy consisted of an ACE inhibitor, a statin, and a diuretic. A calcium channel blocker was not necessarily part of the therapy unless blood pressure could not be controlled on an ACE inhibitor and a diuretic alone. With this combination, medical therapy proved to be as beneficial as more aggressive therapy with angiography and with stenting. The patient has significant renal failure, and gadolinium is relatively contraindicated because this may predispose to nephrogenic systemic fibrosis. In fact, further investigation at this point is not indicated because the patient's renal function is stable. Similarly, an angiogram is not indicated. Increasing the diuretic is not indicated because the diuretic is already on board and the presumption is that the dose is adequate. The final choice is not indicated unless there is rapid deterioration of renal function, and even then, there are no data to support that intervening with angiography and percutaneous angioplasty is helpful.
- a. The two-kidney, one-clip Goldblatt model.The other choices do not allow for natriuresis/diuresis from the opposite unclipped kidney. Thus, those two models are volume-dependent causes of hypertension rather than angiotensin dependent.
- d. Medical intervention is equal to percutaneous angioplasty with stenting. Surgical intervention and or percutaneous angioplasty under certain circumstances may be indicated—specifically, if blood pressure cannot be well controlled medically or there is very rapid deterioration of renal function.The results of the trial are clearly outlined in the text and require no specific explanation.
- b. Retrograde filling of the distal renal artery by collateral circulation on radiographic or scintigraphic imaging studies is more likely to result in a successful surgical outcome. As stated in the text, a kidney less than 8 cm in length cannot be successfully revascularized because it has reached end-stage.Most patients with renal vascular disease have significant vascular disease elsewhere. Renal artery correction and aortic aneurysm correction need not be done simultaneously. A renal ostial lesion may be corrected by percutaneous angioplasty and stenting depending on its radiologic appearance.
- b. Proinflammatory cytokines and/or angiotensin II.Renal blood flow and perfusion may sometimes be maintained at baseline in patients with ischemic nephropathy. Ischemic nephropathy can reverse, and it is is not secondary to a failure of autoregulation alone, as explained in the text. Many patients with progressive ischemic nephropathy have collateral circulation.
- There is an extremely high morbidity and mortality rate in patients who require dialysis due to end-stage renal disease resulting from atherosclerotic renal artery occlusion.
- There are two major pathologic causes of renal artery disease: (1) atherosclerosis and (2) fibrous dysplasia.
- In unilateral renal artery stenosis with a normal contralateral kidney, hypertension is due to angiotensin-induced vasoconstriction.
- In bilateral renal artery stenosis or in renal artery stenosis in a solitary kidney, hypertension is due to volume overload.
- Computed tomographic (CT) angiography and magnetic resonance angiography do not visualize the distal renal arterial tree well.
- Except in rare circumstances, functional testing for renal vascular hypertension has been largely replaced by anatomic imaging of the renal artery lesions.
- Causes of renal vascular hypertension in children include fibromuscular dysplasia, vasculitis, neurofibromatosis, and neuroblastoma.
- Widespread glomerular hyalinization indicates irreversible ischemic renal injury and suggests that there would be little benefit from relief of renal artery obstruction.
- Extensive atherosclerotic disease precludes renal revascularization.
- When the aorta is severely diseased, renal revascularization on the left may be accomplished with a splenorenal bypass, and on the right with a hepatorenal bypass or a supraceliac lower thoracic aorta renal bypass.
- A transient deterioration of renal function is not infrequently seen following a contrast load in patients with significant renal artery stenosis and limited renal function.
- Atherosclerotic renal artery disease generally involves the ostium of the proximal renal artery. Fibromuscular disease usually occurs in white females, often is bilateral, and involves the distal portion of the renal artery.
- At least 70% to 80% renal artery occlusion is necessary to produce clinical effects.
- The decrease in renal function occurring with renal ischemia is primarily due to proinflammatory mediators that result in fibrosis.
- Perimedial and intimal fibroplasia, if left untreated, progress and result in loss of renal function.
- In patients with atherosclerotic renal artery stenosis, there is no significant difference between patients treated medically and those treated with angioplasty.
- If blood pressure cannot be well controlled medically or there is very rapid deterioration of renal function, surgical intervention and or percutaneous angioplasty may be indicated.
- A kidney less than 8 cm in length cannot be successfully revascularized because it has reached end-stage.