Friday, October 5, 2012

Less is More


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

4 comments:

Ahad Abdalla said...

While I agree that the chances of picking up an obstructed kidney as the cause for an episode of AKI, I would not fully support this approach.
The renal ultrasound as a trainee gives much more than excluding obstruction. The size of the kidneys in a patient where no previous renal function results are available can indicate whether this presentation is likely to be chronic or not. The thickness of the cortex another telling sign. The presence of a solitary kidney (impacting on the decision to biopsy). The echotexture of the kidneys. And of course that one time when they do turn out to have an obstruction!
As such it has more implications than just outruling hydronephrosis and as a nephrology trainee I believe it is essential in evaluating an episode of AKI.

Tomoki Tsukahara said...

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

Ryan Evans said...

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.

Tomoki Tsukahara said...

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