Editing Renal Hypertension (section)

== Management of Renovascular Hypertension ==

* May not always be able to reliably assess the significance of a renal arterial lesion before intervention; may need to assume a causal relationship between the lesion and the presence of hypertension
* '''Options for BP control (3):'''
*# '''Medical therapy'''
*# '''Percutaneous transluminal renal angioplasty (PTRA) (with or without stenting)'''
*# '''Surgery'''

* '''Medical Therapy'''
** '''Medical therapy alone may achieve BP control in > 90% of patients with renovascular hypertension'''
** Although all classes of antihypertensives may be used, '''drugs that inhibit angiotensin II production (ACE inhibitors) or block its receptor site (ARBs) have been shown to be particularly efficacious''' because the hypertension is often the result of activation of the renin-angiotensin system
*** ACE inhibitors act on both afferent and efferent arteriole but more on efferent
*** '''ACE inhibitors are contraindicated in bilateral renal artery stenosis'''
** '''Despite BP control with medical therapy, atherosclerotic renal artery lesions may progress with time.'''
** '''Medical therapy may reduce BP below a critical level and induce ongoing renal ischemia;''' '''renal function should be closely monitored whenever such antihypertensive agents are used in patients with renovascular hypertension'''
** '''If blood pressure cannot be well controlled medically or there is very rapid deterioration of renal function, percutaneous angioplasty or surgical intervention may be indicated'''
* '''Percutaneous Transluminal Renal Angioplasty (PTRA) and Stenting for Hypertension'''
** '''Can be successful in treating fibromuscular dysplasia'''; although successful, a restenosis rate of up to 27% may be seen
** '''Unlikely to be successful in treating atherosclerotic RAS'''
*** '''Recent trials have shown in patients with atherosclerotic RAS, no significant difference between medically treated patients and those treated with PTRA'''
**** CORAL trial
***** Showed only a 2 mm Hg difference in BP between groups. This did not translate into a significant decrement in clinical events and it exposed the patients to the potential risks of angiography.
***** Patients with accelerated hypertension flash pulmonary edema and malignant hypertension were not included in this trial. Therefore, conclusions regarding these patients cannot be drawn from this or other studies.
* '''Percutaneous Transluminal Renal angioplasty (PTRA) and Stenting for Preservation of Renal Function'''
** See CW11 Figure 45-8 for management of patients with arteriosclerotic renal artery stenosis algorithm
** '''Non-ostial lesions:'''
*** '''PTRA shows a success rate similar to that of surgical revascularization and poses a lower risk of morbidity and mortality'''
** '''Ostial lesions'''
*** '''Comprise the vast majority (80-85%) of atherosclerotic RAS'''
*** '''PTRA without stenting is far less successful and effective; thus, most''' '''PTRA for atherosclerotic RAS are performed with endovascular stent placement'''
* '''Surgical Revascularization for Renal Artery Stenosis'''
** See CW11 Figure 45-9 for management of patients with fibromuscular dysplasia algorithm
** '''Indications for surgical treatment of RAS (5):'''
**# '''Concomitant aortic aneurysmal or occlusive disease; however; renal artery correction and aortic aneurysm correction need not be done simultaneously'''
**# '''Macroaneurysms of the renal artery associated with stenosis'''
**# '''Malignant or accelerated hypertension (with or without acute renal failure) that did not respond or cannot tolerate medical therapy'''
**# '''>75% occlusion occurs either bilaterally or in a solitary kidney'''
**# '''Those in whom PTRA is technically impossible'''
** '''The traditional criteria that will ensure the best outcome of surgical revascularization of a renal artery are (5):'''
**# '''Kidney > 8 cm in length'''; < 8 cm cannot be successfully revascularized because it has reached end-stage
**# '''Retrograde filling of the distal renal artery by collateral vessels''' on radiographic or scintigraphic imaging studies
**# '''Patency of the distal renal artery'''
**# '''Viability of the involved kidney on isotopic renography'''
**#* With severe renal loss (serum creatinine > 4 mg/dL), the likelihood of renal recovery is substantially reduced and revascularization is not recommended.
**# '''Minimal glomerular sclerosis and well-preserved tubules on renal biopsy'''; widespread glomerular hyalinization indicates irreversible ischemic renal injury and suggests 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
* '''Renal denervation for resistant hypertension'''
** Endovascular radiofrequency ablation (RFA) of the renal artery results in destruction of the renal sympathetics and is being increasingly utilized for management of pharmacologically resistant hypertension.
*** Sympathetic innervation to the kidneys run in the adventitial wall of the renal arteries. Stimulation of the renal sympathetics results in a decrease in renal blood flow, an increase in renin secretion, retention of sodium and water, and hypertension.
*** '''Ablation of the renal sympathetics results in dilation of the renal efferent arteries, decreased plasma renin activity, and increased renal blood flow'''
*** '''Renal artery RFA has no effect on parasympathetic nerve activity'''
*** It has been associated with rare intimal dissections of the renal artery and renal artery aneurysms that may require emergent nephrectomy
** '''Recently shown to be unsuccessful''' (SIMPLICITY trial)