Renal artery revascularization: is there a rationale to perform?

Gray-Scale, Color Doppler, Spectral Doppler, and Contrast-Enhanced Renal Artery Ultrasound: Imaging Techniques and Features

Renal artery stenosis (RAS) is increasingly being detected in elderly patients as life expectancy increases. RAS induces hypertension or reduces renal function. Computed tomography or magnetic resonance angiography are objective in detecting RAS but may cause iodine-induced nephrotoxicity or nephrogenic systemic fibrosis in patients with RAS. Ultrasound (US) is, by contrast, a noninvasive and real-time imaging modality useful in patients with reduced renal function. Renal US is not as sensitive for detecting RAS because this technique indirectly assesses the renal artery by analyzing intrarenal hemodynamic changes. Although, ideally, US would be used to directly evaluate the renal artery, its current utility for RAS detection remains unclear. The purpose of this review is to introduce how to assess renal artery with US, to describe imaging features of renal artery US, to compare renal artery US and renal US, and to show how to perform work-up in patients in whom RAS is suspected.

Decrease of glomerular filtration rate may be attributed to the microcirculation damage in renal artery stenosis

BACKGROUND

The decrease of glomerular filtration rate has been theoretically supposed to be the result of low perfusion in renal artery stenosis (RAS). But the gap between artery stenosis and the glomerular filtration ability is still unclear.

METHODS

Patients with selective renal artery angiogram were divided by the degree of renal artery narrowing, level of estimated glomerular filtration rate (eGFR), respectively. The different levels of eGFR, renal microcirculation markers, and RAS severity were compared with each other, to determine the relationships among them.

RESULTS

A total of 215 consecutive patients were enrolled in the prospective cohort study. Concentrations of microcirculation markers had no significant difference between RAS group (RAS ≥ 50%) and no RAS group (RAS < 50%) or did not change correspondingly to RAS severity. The value of eGFR in RAS group was lower than that in the no RAS group, but it did not decline parallel to the progressive severity of RAS. The microcirculation markers presented integral difference if grouped by different eGFR level with negative tendency, especially that plasma cystatin C (cysC) and urinary microalbumin to creatinine ratio (mACR) increased with the deterioration of eGFR, with strong (r = -0.713, P < 0.001) and moderate (r = -0.580, P < 0.001) correlations. In the subgroup analysis of severe RAS (RAS ≥ 80%), the levels of plasma cysC and urinary mACR demonstrated stronger negative associations with eGFR, (r = -0.827, P < 0.001) and (r = -0.672, P < 0.001) correlations, respectively.

CONCLUSIONS

Severity of RAS could not accurately predict the value of eGFR, whereas microcirculation impairment may substantially contribute to the glomerular filtration loss in patients with RAS.

Renal artery stenosis-when to screen, what to stent?

Renal artery stensosis (RAS) continues to be a problem for clinicians, with no clear consensus on how to investigate and assess the clinical significance of stenotic lesions and manage the findings. RAS caused by fibromuscular dysplasia is probably commoner than previously appreciated, should be actively looked for in younger hypertensive patients and can be managed successfully with angioplasty. Atheromatous RAS is associated with increased incidence of cardiovascular events and increased cardiovascular mortality, and is likely to be seen with increasing frequency. Evidence from large clinical trials has led clinicians away from recommending interventional revascularisation towards aggressive medical management. There is now interest in looking more closely at patient selection for intervention, with focus on intervening only in patients with the highest-risk presentations such as flash pulmonary oedema, rapidly declining renal function and severe resistant hypertension. The potential benefits in terms of improving hard cardiovascular outcomes may outweigh the risks of intervention in this group, and further research is needed.