Biliary POCUS & Surgical Referral

Biliary

Point-of-care biliary ultrasound in the emergency department (BUSED): implications for surgical referral and emergency department wait times

Trauma Surg Acute Care Open - Pubmed Link


Take Home Points

1. Positive findings on an emergency department biliary POCUS is predictive of eventual cholecystectomy, but the exam has a poor overall sensitivity.

2. ED length of stay is shorter when a POCUS study is performed compared to when a POCUS study and a comprehensive study are performed.


Background

Cave paintings found by archeologists indicate that people have been using point-of-care ultrasound to diagnose biliary pathology for at least 35,000 years. Even if that is not true, many people recognize that looking at the gallbladder is not too hard and can really help when there is a biliary problem. There have been studies showing that point-of-care ultrasound has a sensitivity and specificity in the mid to high 80s for the diagnosis of cholelithiasis and cholecystitis (Jain 2017, Ross 2011, Summers 2010). There are obvious benefits - it is faster to perform and can therefore expedite potential surgical management. However, it’s no small thing to put someone under the knife; and therefore, understandably, many surgeons may be hesitant to take someone to the operating room without a confirmatory radiology-based ultrasound. Therefore, this study wanted to take a look to see just how good POCUS can be and also if it actually helps management in the ED.

Read more about the evidence of biliary ultrasound in the The Evidence Atlas.


Questions

What is the predictive value of biliary POCUS in terms of the need for cholecystectomy?

What is the impact of POCUS on the patient's experience?


Population

Single tertiary care center in Ontario, Canada.


Inclusion:

  • Adults who received point-of-care biliary ultrasound who received ultrasound by certain select providers

Exclusion:

  • <18 years old

  • No biliary images recorded


Study period December 1, 2016 to July 2017 (about 7-8 months)


Design

Retrospective cohort study


They found emergency physicians who regularly use biliary POCUS. They looked up all of the studies these providers performed during the study period.

These images were evaluated by a reviewer (fellowship trained in emergency ultrasound) to record the findings.

Electronic medical record reviewed to find additional imaging, laboratory tests, referrals, disposition, length of stay, surgical procedures, and discharge diagnoses.

Primary outcome was diagnostic performance of biliary POCUS in its ability to predict the need for eventual cholecystectomy.

Secondary outcomes were evaluating which ultrasound parameters were predictive of cholecystectomy, providers’ decision to obtain comprehensive ultrasound, and referrals to specialty services.

Of note: if interpretation of a sonographic finding was not present on review of imaging, it was assumed to be negative

Patient centered outcomes were return to the emergency department (ED) with abdominal pain and length of stay in the ED.


Who did the ultrasounds?

Eight Emergency physicians who “frequently use point-of-care biliary imaging to evaluate abdominal complaints”. Met ACEP guidelines for competency in biliary application. No additional training for this study.


The Scan

Curvilinear Transducer

curvilinear

This study specifically looked for:

  • Presence of gallstones

  • Pericholecystic fluid

  • Gallbladder wall thickness >4 mm (or subjectively called thickened)

  • Sonographic Murphy’s sign


5minsono

5 Min Sono - Gallbladder


thePOCUSAtlas

The Image Atlas - Hepatobiliary


Results

N = 283 patients

  • 29% referred for general surgery evaluation

  • 43% ultimately received cholecystectomy

  • 30% referred for comprehensive imaging in the ED

  • 95% had comprehensive imaging prior to cholecystectomy


Primary Outcome

Performance of POCUS in predicting cholecystectomy

Sensitivity 63% (CI 48-78)

Specificity of 89% (CI 84-93)


Secondary Outcomes

Sensitivity, Specificity, and Odds ratios (from multivariate regression) for findings on POCUS for predicting cholecystectomy

  • Gallstone - 55% sensitive (CI 40-70) , 92% specific (CI 87-95) OR 13

  • Gallbladder wall thickening - 18% sensitive (CI 9-33), 98% specific (CI 95-99), OR 4.8

  • Sonographic Murphy’s sign - 15% sensitive (CI 7-30), 95% specific (CI 92-97), OR 2.68

  • Biliary tree dilation - OR 10.6 but not statistically significant

*Only 1 patient in this cohort had pericholecystic fluid so they did not calculate test characteristics.


Biliary tree dilation (n = 3) was only finding significantly associated with unexpected return to the emergency department, OR 33.67 (CI 1.8-630.7)


ED Length of Stay

POCUS imaging alone: 309 minutes ± 30 minutes (5.15 hrs)

POCUS + Comprehensive imaging: 433 minutes ±50 minutes (7.22 hrs)(p < 0.001)

So basically you save about 2 hours. Unless you were discharged and asked to come back for radiology based imaging, then it took 16 hours.


Other Findings

100% of cholecystectomies had pathologic evidence of cholecystitis

3/283 patients who had cholecystectomy did not have gallstones on pathology


Limitations

Retrospective - risk for bias. As this paper states (written by both surgeons and EM physicians), “providers may have documented their findings in the chart after they received feedback from their surgical colleague.” Providers may have only saved good studies and not saved studies that were inadequate or difficult. Also remember that absent findings were considered negative - this had the potential to change the test characteristics, likely would increase false negatives leading to lower sensitivity. Also, since the return visits and surgeries were tracked by chart review alone, there could have been missed encounters at different hospitals or systems.

Only took the ultrasounds of selected “advanced” ultrasound providers. This limits the external validity. Furthermore, and even more concerning, it is unclear whether the original interpretation or the overread of each exam by an expert was used to determine accuracy. Would prefer to see the accuracy based on the initial interpretation. Otherwise, this study is performed is more akin to a radiologist based accuracy, instead of an integrated-with-clinical-care point-of-care ultrasound.

There is a problem with the primary outcome - eventual cholecystectomy. There is no mention in the paper about the timeline for this procedure. The abstract mentions 28 day follow up but that is not mentioned in the manuscript methodology. This is a problem for two reasons: 1) Having cholecystitis now and having cholecystitis in a month will probably result in different emergency department visits 2) The fact that cholelithiasis causes cholecystitis makes it difficult to understand from this study if the POCUS is identifying cholecystitis, or merely identifying those at risk for cholecystitis. It seems almost as though the authors don’t care about these problems. Perhaps their reasoning is, well if the POCUS is a false negative - there will be radiology studies to make sure nothing is missed. If the POCUS is a false positive - well, they were probably going to need their gallbladder out anyways.

There are a few other “leaps” in thinking from the authors in the discussion section. They assume that because many patients who received POCUS were referred to surgery, and many that were referred had cholecystectomy - that POCUS must be useful in increasing the threshold for referral and the accuracy of referral. This is unfounded without the comparison of a control group. There is no way to say whether POCUS helped or if it actually led to more unnecessary consultations. Furthermore, they did not confirm that the general surgery consultation after a POCUS was actually for biliary concerns. What if, after receiving POCUS, the patient was found to have a small bowel obstruction? If surgery was appropriately consulted, this could have theoretically counted as surgical referral which did not result in cholecystectomy. They also assume that having more faith in POCUS would lead to less returns for comprehensive studies. I guess that depends on who is dictating these follow up studies and why they need these studies after their ED visit. These patients are being discharged after all - did the ED physicians think they just had cholelithiasis? Did they think there was cholecystitis but sent them home anyway? It seems there is some behind the scenes protocol in place. It would be useful to know what the standard practice was for when studies and referral were ordered as well as disposition decision. It likely involved clinical status and laboratory results as well as the ultrasound.


Discussion

The authors propose that these results be applied suchly: if you have a patient with a good clinical story for biliary symptoms, without high risk features, without more likely alternative diagnosis + positive POCUS findings → surgeons consider offering cholecystectomy. That doesn’t sound unreasonable at face value, but in order to have a full understanding of the evidence, we really need to know how soon these patients had their surgeries. If it is surgery now when it could have been several months from now - well, maybe that is not the best idea.

Authors state that only half of scans reviewed mentioned the presence or absence of gallstones. They use this as evidence that POCUS exams need better or more standardized documentation. I agree that we need good and clear documentation, but not necessary that you have to document every negative finding in a study. It depends on the question(s) you are trying to answer. On the other hand, these are physicians who were selected for their routine use of POCUS, and the finding of gallstones is likely relevant to most biliary scans. Come on guys.

This paper does a nice job looking at a patient centered outcome - the need for surgery. It would have been really nice if they had reported other patient centered outcomes, such as surgical complications and mortality. Theoretically, POCUS could save some time and lead to better outcomes; however, this outcome was not addressed in this study and would have been difficult to interpret without a control.


Take Home Points

1. Positive findings on an emergency department biliary POCUS is predictive of eventual cholecystectomy, but the exam has a poor overall sensitivity.

2. ED length of stay is shorter when a POCUS study is performed compared to when a POCUS study and a comprehensive study are performed.


Our score

1 Probe


Expert Reviewer for this Post

Au

Arthur Au, MD @arthurkau

Arthur is the Associate Ultrasound Director and Ultrasound Fellowship Director for the Department of Emergency Medicine at Thomas Jefferson University in Philadelphia, PA.


Reviewer's Comments

I approached this paper and their study question with great interest. One of my greatest frustrations in patient care and ED flow is when consulting services ask for confirmatory radiology studies prior to evaluating or intervening on patients with clear cut findings on point of care ultrasound. Lack of clarity and key omissions in the methods make this paper difficult to interpret. It is reaffirming that patients with findings consistent with cholecystitis on ED POCUS will go on the get cholecystectomies. However, this outcome alone is unlikely to convince surgeons that confirmatory studies are unnecessary. A subgroup analysis of patients referred to surgery without additional imaging as well as factors such as morbidity/mortality due to delayed surgery while awaiting additional imaging would have been of particular interest. Unfortunately this is a missed opportunity in a collaborative effort with our surgical colleagues.


Cite this article as

Michael Prats, MD. Biliary POCUS & Surgical Referral. Ultrasound G.E.L. Podcast Blog. Published on February 04, 2019. Accessed on June 17, 2019. Available at http://www.ultrasoundgel.org/62.
Published on 02/04/19 06:00 AM
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