A POCUS Protocol for Renal Colic

By Michael Prats

Renal Colic Graphic

Usefulness of Protocolized Point-of-Care Ultrasonography for Patients With Acute Renal Colic Who Visited Emergency Department: A Randomized Controlled Study

Medicina Oct 2019 - Pubmed Link


Take Home Points

1. An ultrasound protocol, even with subsequent CT, can save time and cost for patients with suspected renal colic depending on your current practice.

2. The time savings in this study stems from decreasing time to non-contrast CT imaging. Time benefit may disappear if CT is ordered prior to labs.

3. More research needs to be done using protocols that use ultrasound to avoid CT imaging when appropriate.


Background

While non-contrast CT has traditionally been the “gold standard” imaging test for suspected renal colic, there has been recent research and guidelines that have started to shift the paradigm towards the responsible utilization of renal ultrasound as an alternate imaging strategy (in appropriately selected patients of course). The landmark NEJM Smith-Bindman study from 2014 was the big game changer in this arena. It was a large, multicenter, randomized trial directly comparing ultrasound against non-contrast CT in the evaluation of ED patients with suspected renal colic. This study revealed no difference in adverse events or diagnostic accuracy between the study arms, though radiation dosage was higher in the CT arm. Finding hydronephrosis can clue us in that there is a significant obstruction from that stone; although, we know from other studies that this finding is not that sensitive or specific. We reviewed a study previously that showed that the finding of hydronephrosis is most impactful when there is a great deal of it in patients with a low pre-test probability. Unfortunately, we also looked at a study showing that emergency physicicians’ interpretation of the ultrasound doesn’t always line up with radiology (and both don’t line up with CT). What remains to be determined is what to do when you find hydronephrosis. Does this mean get a CT to confirm? Does this mean just treat their pain as if they had a stone? There was a fascinating article published recently that attempted to obtain consensus on the appropriate imaging for patients in different specific scenarios but there is still significant variability in practice. The article at hand examines one protocol using point of care ultrasound in suspected renal colic to see if maybe it can save some time and cost for the patient.


Check out The Evidence Atlas - Renal for a review of prior evidence on point of care renal ultrasound.


Questions

In patients with suspected renal colic, does a point-of-care ultrasound protocol reduce diagnostic time or medical expense (without increased complications) compared to routine clinical practice?


Population

Study took place in Seoul, South Korea

Single academic tertiary hospital - Samsung Medical Center (also they used Samsung ultrasound machines)


Inclusion:

  • Patient with suspected acute renal colic (not further described)


Exclusion:

  • <18 years old

  • Pregnancy

  • Intraabdominal malignancy or metastatic cancer

  • Urinary stones within past 30 days

  • Urogenital abnormality

  • Fever (>37.2 degrees C)

  • Trauma

  • Suspected herpes zoster

  • Refused consent

  • Language barrier

  • Patient who underwent procedures for symptoms or diagnosis while in the ED


Design

Prospective "randomized" controlled trial

Patients presented with possible renal colic

If on odd day of the month → conventional treatment consisting of history, physical exam, serum testing (complete blood count, electrolytes, chemistry), urinalysis. Physicians could then decide if imaging was indicated. Unclear if they could choose to get an ultrasound in this group.

If on even day of the month → ultrasonography group. First received bedside ultrasonography to look for hydronephrosis, during history and physical exam. If hydronephrosis was found → non-contrast abdominal CT was performed. They only obtained UA and creatinine. If no hydronephrosis → they received the additional labs like in the conventional group.

All patients diagnosed with ureteral stone were followed up 30 days after diagnosis. This was done by outpatient urology follow up, outpatient visit, or phone call. Checked for acute kidney injury or complicated UTI. Also looked for missed diagnoses based on review of electronic medical record.


Primary Outcome was ED length of stay

Secondary outcomes were ED medical cost, incidence of acutely missed or delayed high-risk diagnosis, complications within 30 days.


Power calculation → need 152 patients total


Who did the ultrasounds?

12 attending emergency physicians and 14 residents of the emergency department

Underwent 4 hour education (1.5 hrs didactic, 2.5 hrs hands on) and 10 cases of practice training


The Scan

Curvilinear Array transducer

Curvi


Obtained 2D image and color doppler (to distinguish collecting system from renal vessels)

Both kidneys examined

Short and long axis views obtained


Learn how to do Ultrasound for Hydronephrosis from 5 Minute Sono!

5minsono


Check out GU Pathology on the POCUS Atlas!

thePOCUSAtlas


Results

218 patients with suspected renal colic.

  • Largest exclusion was failure to get consent (n= 16), then history of urinary stone within 30 days (n = 12), and “erroneous group match” (n=12), then a handful of the other things. 152 were randomized but then 5 were excluded due to procedures.

N = 147

  • 74 in standard conventional group, 73 in ultrasound

  • 87.1% of population had ureter stone

  • No significant difference in characteristics of groups

  • Mean age late 40s to mid 50s

  • Majority male patients


Primary Outcome - ED Length of Stay

Conventional Group - 234 minutes (CI 216-252)

Ultrasound Group - 172 minutes (CI 151-194)

Difference 62 minutes (26.5% reduction). Basically 4 hrs vs 3 hrs.


Subgroup of those with ureter stones saved slightly more time, 74 minutes difference (32% reduction).


Secondary Outcomes

Medical Cost

Conventional Group - $319 USD (CI 319)

Ultrasound Group - $259 USD (CI 240-278)

Difference $60 USD


Time from CT to ED discharge was not different between group.

No significant difference in 30 day complications and missed diagnosis between groups. Both groups had 0 missed diagnoses. Most complications were requiring extracorporeal shock wave lithotripsy or presenting to another hospital prior to follow up.


Other Findings

They report test characteristics of their POCUS for hydronephrosis compared to CT:

  • Sensitivity 72%

  • Specificity 83%


Limitations

Randomization by date without blinding to physicians. Pain control time not recorded - could have influenced length of stay and would have been nice to compare between groups. No serum testing for those with only telephone follow up.

Author’s note that the time from CT scan to ED discharge was not significantly different between groups. We also know that all (or at least most) of their patients received a CT scan (no number is actually reported but we know that most roads led to CT in their algorithm and they list all patients as having a “time from CT to discharge”. Therefore, the time savings appears to be in getting the patient to CT scan. Since there is no mention of a “time to provider”, there is potential for confounding in that one group could have received faster care on the front end. In comparing the two protocols - both received history and physical exam but conventional group received more labs and a urinalysis whereas the ultrasound group received the POCUS prior to obtaining CT. The conclusion is therefore that performing an ultrasound takes about 1 hour less than waiting for labs. That is less than stunning information. I am not sure the best way (for patients) to save time and money is to just lower threshold for imaging.

Regarding the population, there are a few strange exclusion criteria. Fever - it seems unnecessary to exclude this. A fever (especially with their unusually lax definition of >37.2 C or 98.9 F) is unlikely to cause hydronephrosis and all they are doing it seems is to remove possible pyelonephritis from the differential. Unfortunately, an infected stone is often a possibility and it would have been nice to apply this data to that population. It is too bad that patients who received treatment for obstructing nephrolithiasis (such as lithotripsy) were excluded, but this makes sense given their outcome of length of stay. Overall, there may be some bias in this population, and they tuned it into a fairly high pre-test probability group (as evidenced by their 87.1% prevalence of disease). They also reported 0 missed diagnoses. This is not consistent with other literature and makes their protocol suspect - it could be either that their exclusion criteria were too stringent or because they CT’ed everyone.

Per the authors, it is normal to perform CT scan in patients with suspected renal colic. Therefore, this protocol was helpful in that it got patients to CT scan more quickly. Whether or not this is going to be helpful for you and your patients depends highly on your current imaging practices.

There is no mention of how the cost numbers are calculated. This took place in Korea but the calculations are in US dollars. It is odd to not describe how these calculations took place. The cost reduction applicability is low unless you are working in the the same environment of this study.


Discussion

In this study, anybody with diagnostic testing supported ureterolithiasis (hydronephrosis or hematuria) received a CT exam. Therefore, the idea of this study is that POCUS can get the patients to CT faster. I think that this is not the best approach. I think the main benefit of POCUS in these patients is that it allow you to AVOID a CT in many patients - such as those in whom you have made the diagnosis of renal colic and do not have significant hydronephrosis. It would have been great if this study’s protocol included an option to not get CT, likely would have saved radiation and even more time. See this landmark article on the issue.

The real question is who can you safely avoid CT on? The other aforementioned article on a multi-specialty imaging consensus sheds some light on this issue . In this articles, there is perfect agreement that a fairly young patient with a history of nephrolithiasis, a history and exam consistent with renal colic who has hydronephrosis or has no hydronephrosis on the symptomatic side does not need any additional imaging if his pain is relieved.

Although this study is far from conclusive in demonstrating a cost benefit, the potential is still there. It is feasible that a point-of-care ultrasound will be cheaper than a CT and in addition to avoiding unnecessary radiation, you might save your patient some money.


Take Home Points

1. An ultrasound protocol, even with subsequent CT, can save time and cost for patients with suspected renal colic depending on your current practice.

2. The time savings in this study stems from decreasing time to non-contrast CT imaging. Time benefit may disappear if CT is ordered prior to labs.

3. More research needs to be done using protocols that use ultrasound to avoid CT imaging when appropriate.


More Great FOAMed on this Topic

ALIEM - Author Insight: Ultrasonography versus CT for Suspected Nephrolithiasis

Core EM - Ultrasonography vs CT in Renal Colic


Our score

2 Probes


Expert Reviewer for this Post

Thom

Christopher D Thom, MD RDMS @ThomCt9k

Assistant Professor of Emergency Medicine and the Assistant Director of Emergency Ultrasound at the University of Virginia


Reviewer's Comments

This one is a bit tough. It’s great to see ultrasound for renal colic do well, but this study misses the key point regarding why we do ultrasound in evaluation of renal colic (i.e. - to avoid doing CT”s on everyone). It’s true that POC ultrasound could be quicker, and it could be cheaper, but this is probably because the utilization of ultrasound can supplant the need for CT in many cases of renal colic. In this study, pretty much everyone in both arms got CT’d (though exact numbers not provided), so the main thrust of why we do POC ultrasound for renal colic eval is completely missed. If they hadn’t felt the need to CT everyone with hydronephrosis, then the data could be pretty interesting, as the time savings could be important if the safety outcomes still held up.


Cite this post as

Michael Prats. A POCUS Protocol for Renal Colic. Ultrasound G.E.L. Podcast Blog. Published on March 02, 2020. Accessed on September 21, 2020. Available at https://www.ultrasoundgel.org/87.
Published on 03/02/20 05:00 AM
comments (0)