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There's a physician that always takes blood pressures bilaterally for EVERY patient he sees. These patients are assumed to be healthy adults coming in for basic routine medical exams.

I don't see any advantage of doing this....

  1. What is the rationale behind this (if any)?
  2. Assuming there is a difference -- what would that even mean?
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Because that's the way to measure blood pressure

The German guidelines for treating hypertonia are to always measure bilateral. (German Source Only)

As @DoctorWhom pointed out in the comments, atherosclerosis1 and ascending aortic dissection2 can lead to difference in the blood pressure.

Furthermore, as a study fairly recently conducted (2012) found, not measuring bilaterally can have other devastating effects as well: An undetected difference in blood pressure greater than 15 mmHg increases the overall mortality by 60%, and cardiovascular mortality even by 70%. Furthermore, the risk of suffering from an undiagnosed PAD (peripheral artery disease)3 increases by factor 2.5.

The study concludes that

A difference in SBP of 10 mm Hg or more, or of 15 mm Hg or more, between arms might help to identify patients who need further vascular assessment. A difference of 15 mm Hg or more could be a useful indicator of risk of vascular disease and death.
(Link to whole study)

Furthermore, the chances of a wrong reading are significantly lower if verified once.

1: Atherosclerosis is a form of arteriosclerosis where the artery wall thickens, thus leading to an increased blood pressure in this artery (and depending on the location, can lead to a difference between L and R blood pressure).

2: The aortic dissection is a tear in the wall of the aorta. As the tear extends along the wall of the aorta, blood can flow in between the layers of the blood vessel wall (dissection). This can lead to aortic rupture or decreased blood flow (ischemia) to organs. A decreases blood flow will result in lower blood pressure. Thus measuring L and R gives one a quick overview and a faster way of ruling aortic dissection out than sending the patient to the CT.

3: PAD's is a broad term for the narrowing of arteries different from coronary arteries and cerebrovascular arteries. Depending on the location of narrowing, a difference in blood pressure between L and R can occur).

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    Thank you!!! He actually is from Germany -- makes sense! – Mike-DHSc Sep 15 '17 at 5:42
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    I really don't have time to flesh my answer out now, but I might do it later to explain why it's a useful indicator. – Narusan Sep 15 '17 at 5:44
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    No rush -- was just something I could never wrap my head around and never found any rationale to do so.. – Mike-DHSc Sep 15 '17 at 5:45
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    @Mike-DHSc great question! It's not commonly done here in the US but should be, IMHO, since Narusan is correct. But I think for time shortage reasons we often don't. I do it manually now and then to verify a particularly high or low reading before making significant changes in meds etc. – DoctorWhom Sep 15 '17 at 6:14
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    @Narusan-in-coma a couple things to add: among the reasons for difference between R and L are the most common atherosclerosis (or muscular spasms) and less common but serious ascending aortic dissection. If suspecting dissection, that's one test that's easy to do before sending for CT. But it's pretty rare, so don't worry that is the reason your SBP are different - like you said, it's normal to vary. – DoctorWhom Sep 15 '17 at 6:16

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