Less is More

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Despite the fact that the
kidney ultrasound is generally obtained as one of multiple recommendations when
evaluating AKI, the benefit of kidney ultrasound is not clear. The post-renal
causes of AKI are not very common. It
adds to the cost and can subject patients to unnecessary work-ups by revealing
incidentalomas. How often, then, is the ultrasound useful? 
In order to assess the
prevalence of the post-renal AKI and determine a cost-effective use of the
ultrasound, a single-center case-control study was conducted.
Their conclusion is that the
prevalence of hydronephrosis requiring stenting or nephrostomy placement was
only 0.4% in the low-risk group. The number to screen to find a case of urinary
obstruction was 223. At what cost? In our institution the kidney ultrasound
without Doppler costs $600. It costs $133,800 to find one case.
Who is the low-risk group
patient? Based on the multivariate analysis, a patient was considered low-risk
if he or she did not have a history of hydronephrosis and had no more than one
of the following:
1. Recurrent UTI
2. Diagnosis to suspected
obstruction (BPH, abdominal or pelvic cancer, one functional kidney,
neurogenic bladder, pelvic surgery)
3. Non-African American
4. Absence of:  exposure to the following medications (ASA,
diuretics, ACEI or IV vancomycin), congestive heart failure, or pre-renal AKI.
The study has limitations. Not
all AKI patients were studied. The cases requiring non-surgical interventions were
not counted. If we would have to implement this strategy, we don’t know what
the cost of missing some cases of obstruction would be.
However, the implication is
that we should not routinely order kidney ultrasound on every patient with AKI,
particularly those in the low-risk group. In this era of cost constraint on medicine,
less is usually more…
Or, here is what you can do.
If your place has an ultrasound on the floor, with a little training you can
have a quick look at the kidneys just to rule out obstruction in low risk
patients. You acquire one more diagnostic skill, your students have one more
fun on round, and your hospital saves significant amount of money!
Posted by Tomoki Tsukahara


  1. Thanks for your comment, I was surprized too. Yes, this is a hospital charge in the hospital setting (including interpretation fee by radiologist), so as you wrote it may be different from office setting or in other institutions. Interesting comparison. T

  2. I'm surprised at the cost for a renal ultrasound that you quote. $600.00. Is this in a hospital setting? We perform our renal ultrasounds in the office and the payment is a little less than $100.00. Maybe they are reimbursed higher in the hospital.Interesting comparision.

  3. Thanks for your comment and I agree, like you mentioned, in many cases US is not just to rule out obstruction – size, echodensity, cortical thickness, evidence of renal artery stenosis (with Doppler), etc., are all important information. What I learned from this article is that I realized at times I was ordering US like a reflex and was not conscious of its cost. I still order US, but now I think more about indication(s) before ordering it. T

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