April 2018

Paper 10 - Nephrolithiasis

Sign in or subscribe to listen

No me gusta!

The flash player was unable to start. If you have a flash blocker then try unblocking the flash content - it should be visible below.

Sarah A. -

I realize it doesn't matter for LLSA, but am still confused about the conclusions of this discussion and study. It showed that there was no significant difference in outcomes when using ultrasound, but I'm not clear that it showed us that getting the ultrasound contributed anything to patient care either. If my clinical suspicion for nephrolithiasis is reliable regardless of the type of imaging, and the sensitivity of US for confirming evidence of nephrolithiasis is only 54%, and the ultrasound is not capable of identifying other complications or mimics, then why do it? What does it add except time to the patient visit? Why not just treat the patient and send them home, if we have decided that the risk of complications or missed alternative diagnosis is already acceptably low?

For patients who do need imaging, I'm not sure this showed really a clear benefit to US over CT: The average cost savings was only $25. The radiation difference was statistically different between the two groups, but I'm not sure how clinically significant it is, since the average radiation exposure reported in both the US and CT groups over 6 months (10 and 17 mSv) was relatively high, suggesting that the average patient in both groups ultimately got more than 1 CT scan. A high percentage of POCUS patients ended up getting a CT scan anyway on the first visit, which is probably partly why there was no real difference in the time the patient spent in the ER (6.3 vs 6.4 hours). Logically it makes sense to me that the CT scan would be better at detecting dangerous mimics like aortic dissection and appendicitis - if you look at the details of the high risk diagnosis that were missed in the supplementary appendix, the 2 reported in the CT scan group were both UTIs, while the 9 in the US groups included much more frightening missed diagnosis, including bowel ischemia and ovarian torsion. Even scarier is the fact that those misdiagnoses weren't caught for several days afterwards. Even if it is a stone, a CT scan might also be more likely to give us prognostic information, such as the size and location of the stone, or the presence of stranding or thickening concerning for pyelonephritis or abscess, which might be useful for informing follow up care with the urologist or the risk of complications. Altogether, those benefits might be worth the extra $25.

We all love the satisfaction of diagnosing nephrolithiasis at the bedside on US and discharging the patient without delay, but at least according to this study, that practice doesn't really seem to translate into an overall improvement in patient care in terms of cost, time, or clinical outcomes for most patients, especially in a large hospital such as an academic center where CT scan and urology might be readily available. I see this study to be useful for rural community facilities that have neither, in which the question is really: "Can I send this patient home without a CT scan?" or "Does the US give me enough information to make a transfer decision?". The other tempting clinical question would be, "Can US help me distinguish between an obstructive stone and malingering in a frequent flyer?"

To join the conversation, you need to subscribe.

Sign up today for full access to all episodes and to join the conversation.