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Old 05-20-2011
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Sphygmomanometer NBME form 1 question- determinant of BP

A previously healthy 56 year old has sudden onsets of headache that become worse in the afternoons. His blood pressure is 180/100. Renal arteriography shows 80% occlusion of the right renal artery. The laboratory finding that best predicts whether an operation wil help in the reduction of BP is increased renin activity in
1. left renal artery vs right renal artery
2. left renal vein vs right renal vein
3. right renal artery vs left renal artery
4. right renal vein vs left renal vein
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Old 05-20-2011
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Quote:
Originally Posted by meka View Post
A previously healthy 56 year old has sudden onsets of headache that become worse in the afternoons. His blood pressure is 180/100. Renal arteriography shows 80% occlusion of the right renal artery. The laboratory finding that best predicts whether an operation wil help in the reduction of BP is increased renin activity in
1. left renal artery vs right renal artery
2. left renal vein vs right renal vein
3. right renal artery vs left renal artery
4. right renal vein vs left renal vein
I think Renin definitely acts on the Arteriole base, so its left with 1 or 3. Now it will depend on the site of occlusion, and the origin of the artery.

I think I would select 1. Left Renal Artery vs. Right Renal Artery
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Old 05-20-2011
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Hmm, good question...tricky. I think I would select 4. right renal vein vs left renal vein
So the right renal artery is occluded, meaning decreased pressure in the blood getting to the right afferent arteriole and the JGA, so the JGA secretes more renin leading to hypertension. The left renal artery is fine, and the patient has HTN, so there would be increased pressure getting to the left afferent arteriole, and the left JGA would secrete less renin.
Since these changes are occurring in the afferent arteriole, I guess you would see the changes in the veins leaving the glomeruli. By the time the blood circulates through the heart and back to the arteries, the renin would be equal in both left and right renal arteries.
Not sure, stuck between 3 and 4.

Last edited by heights; 05-20-2011 at 10:09 PM. Reason: Changed answer from 3 to 4
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4. right renal vein vs left renal vein
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Old 05-20-2011
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I agree 4 - Rt Renal Vein v/s Lt Renal Vein

Increased plasma renin activity is measured usually in the renal veins than the arteries that leaves us with option 2 and 4.

If only right renal artery is involved as in x-ray then right renal vein should have higher renin activity than Left renal vein. Surgery will correct the BP if this is the only pathology

But if Left renal vein has higher plasma renin activity than the right, then there has to be an additional pathology affecting the left kidney (localized pathology) or both (systemic) - therefore surgical correction of only right renal artery wont correct this persons BP

I could infer this from the question, correct me...
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Old 05-21-2011
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Originally Posted by nevillenic View Post
Increased plasma renin activity is measured usually in the renal veins than the arteries that leaves us with option 2 and 4.

If only right renal artery is involved as in x-ray then right renal vein should have higher renin activity than Left renal vein. Surgery will correct the BP if this is the only pathology

But if Left renal vein has higher plasma renin activity than the right, then there has to be an additional pathology affecting the left kidney (localized pathology) or both (systemic) - therefore surgical correction of only right renal artery wont correct this persons BP

I could infer this from the question, correct me...
I think you are right:

"Another finding of our study indicated that a renin ratio of <1.5:1 was also predictive for treatment failure. In addition, the combination of the RI (Resistance Indices) values of more than 0.55 on the stenotic side with a renin ratio of <1.5:1 indicated the highest risk (OR = 44) for no improvement of hypertension. This close correlation of renin values and RI in the stenotic kidney as predictors for improvement of hypertension might indicate that the probability of detecting truly renovascular hypertension is mainly dependent on the hemodynamic significance of the stenosis and that other factors such as parenchymal changes are of secondary importance."


Duplex Ultrasound and Renin Ratio Predict Treatment Failure After Revascularization for Renal Artery Stenosis.
Am J Hypertens (2006) 19, 756763
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