Consult Rounds: High renal arterial resistive index

The renal arterial resistive index (RI) is a sonographic index to assess for renal arterial disease.

RI = (peak systolic velocity - end diastolic velocity ) / peak systolic velocity

• The normal value is ≈ 0.60
• With 0.8-0.9 being elevated
• The RI measures the resistance of renal arterial flow to the kidney. In cases that cause elevated RI levels, there is reduced flow through the renal artery during diastole and sometimes even reversal of flow during diastole. 

We classically see this in the transplant kidney when there is concern for rejection

What is the differential diagnosis of this finding in a native kidney?

ATN
Obstruction

Renal artery stenosis
Renal vein thrombosis

Pyelonephritis

Severe hypotension

The MORAL of CORAL

The CORAL trial finally has arrived. Stenting the renal vessels has always been a topic of debate.  This is the largest trial to date that directly compared intervention to medical therapy in atherosclerotic renal stenosis.

1. Investigators randomly assigned over 900 patients to either medical therapy or stenting.
2. Cardiovascular or renal events were the end points. - MI, stroke, need for ESRD and or death
3. 43 months of follow up and no different in primary endpoints. No difference in mortality. Blood pressure slight better in stent group
4. Meds that were used in their protocol:- Atacand with or without HCTZ and a combo of CCB and statin.
5. All renal arteries with stenosis >60% or more were treated( prior studies some severe cases were excluded)
6. Close to 50% in both arms had patients with CKD stage 3 or higher( makes it hard to offer stenting already)
7. Looking closely at the data, it appears that there were more strokes in the medical therapy arm but still not statistically significant. Interestingly, more patients reached ESRD in stent arm than medical therapy arm but not statistically significant.
8. Author's recommendation- no significant benefit to stenting in atherosclerotic renal artery disease.

Is this the end of RAS in atherosclerotic renal disease?-I think so!

In the News: The POWER of HERCULES

Renal artery stenosis has taken a story of the classic pendulum swinging.  Studies that were observational in the 1990s suggested benefit in stenting and angioplasty as a treatment of modality. Recent trials such as STAR and ASTRAL ( largest to date) have shown no significant benefit in interventional interventions for atherosclerotic renal artery stenosis(ARAS).

While CORAL is still underway, here comes HERCULES.  This is a large prospective multi-center single arm study of patients with significant RAS and uncontrolled HTN. This is in contrast to prior trails that had less sicker patients. Most were at least on 2 agents and 75% on ACEI or ARBS. The procedure related complications were only 1.5% compared to prior studies suggesting as high as 17%.  The results suggested drop in SBP significantly at 9 months, low in stent restenosis rate and complication rates.

While this is a positive study in terms of intervention- the fact that it is a single arm trial, makes it a major limitation.  HERCULES has limitations too. CORAL is still awaited.

Regardless- check out the full trial at Catheterization and cardiovascular interventions.