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?
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