Diagnostic Imaging

 

Topic 1 - Summary
1. Citation:
  1. Becker, Brent. A., Emergency Biliary Sonography: Utility of Common Bile Duct Measurement in the Diagnosis of Cholecystitits and Choledocholithiasis, The Journal of Emergency Medicine, 2014, Vol. 46, pp. 54-60
2. Summary/Bottom Lines:
  1. The main objective of the study was to determine the prevalence of isolated sonographic CBD dilation in ED patients with cholecystitis or choledocholithiasis without any lab abnormalities or other pathologic findings on biliary ultrasound. 
  2. What they found was that less than one percent of ED patients with cholecystitis requiring cholecystitis or choledocholithiasis presented with isolated sonographic CBD dilation. 
  3. In the setting of a normal ultrasound and normal lab testing, the results suggest CBD measurement has limited use in diagnosing either disease.  
  4. In practice the findings assist clinicians in scenarios which the CBD is unable to be reliably identified sonographically.  Even in the presence of cholelithiasis, a set of normal labs and otherwise unremarkable gallbladder ultrasound should provide reassurance that acute cholecystitis and choledocholithiasis are unlikely to be present. 
3. Methods:
  • This was a retrospective chart review at a single academic tertiary care hospital that included two separate ED patient cohorts between 2000 and 2010. 
  • The first patient cohort consisted of patients undergoing a biliary ultrasound and subsequent cholecystectomy for presumed cholecystitis. 
    • The first cohort consisted of 666 total patients and a total of 2 patients presented with a dilated CBD with both normal labs and an otherwise normal ultrasound. 
  • The second cohort consisted of all ED patients receiving a biliary ultrasound who were ultimately diagnosed withcholedocholithiasis. 
    • The second cohort consisted of 151 patients and was found to have only one patient whose only positive finding was a dilated CBD seen on ultrasound. 
4. Limits:
  1. Some limitations of the study include the fact that it was only performed at a single hospital and other radiologic modalities such as CT were not included.
  2. Also the fact that the ultrasound studies included in the analysis were conducted by the radiology department and not by EM physicians at bedside may limit applicability of the study to ED POC biliary ultrasounds.  
  3. Only acute chole and choledocholithiasis were included in the study and other causes of RUQ pain such as acute pancreatitis and cholangitis were not studied.
5. Additional Info:
  1. It was brought up in discussion that this paper does not tell anything about the specificity of an isolated CBD in these patients
    1. For instance how would this paper guide our clinical judgment if a patient did only present with a dilated CBD with normal labs and normal ultrasound.  Would you still admit the patient or send them home?
  2. It is probably best to take into factor the patient’s clinical presentation such as has their pain improved, are they PO tolerant, etc. 
6. Author: Dr. Matthew McKerley

 

Topic 2 - Summary
1. Citation:

Smith-Bindman R, Aubin C, et al. “Ultrasonography versus Computed Tomography for Suspected Nephrolithiasis.” N Engl J Med. 2014 Sep 18;371(12):1100-10

2. Summary/Bottom Lines:
  • The current gold standard for diagnosing nephrolithiasis is CT, but patients are exposed to radiation and the use of CT over other imaging modalities has not been shown to improve patient outcomes. However, use of ultrasound (U.S.) as an alternative has been problematic due to low sensitivity.
  • This study used an intention-to-treat analysis aimed at identifying differences in patient outcomes when comparing US and CT as the initial imaging test for suspected nephrolithiasis in the emergency department (ED), with additional imaging being used as needed.
  • Patients initially receiving ultrasound (ED point-of-care U.S. or radiology department U.S.) were exposed to less radiation, with no differences in patient outcomes (missed/delayed serious diagnoses, pain, return ED visits, hospital admission after ED discharge), when compared to patients initially receiving CT.
  • Other potential benefits of U.S. included a minor financial benefit ($25 cheaper in patients randomized to radiology US vs. CT) and shorter length of stay (ED US and CT vs. radiology US).
  • The authors don’t suggest using US as the sole imaging test, but they advocate for US as the initial test and supplementing with additional imaging, if indicated.
  • Changes to practice are unlikely to occur on the basis of this article alone, given some outstanding questions about the study’s protocol and methods. Some of the ideas and data expressed in the study are encouraging and might instigate changes in practice after additional studies.
    • Results:
      • U.S. groups were exposed to less radiation (about half) during the initial ED visit, and less cumulative radiation over 6 months.
      • No significant difference in patient outcomes (missed/delayed serious diagnoses, pain, return ED visits, hospital admission after ED discharge)
      • Other benefits: minor financial benefit ($25 cheaper if received radiology US vs CT), shorter ED length of stay (with ED US and CT vs. radiology ultrasound)
    • Results:
      • [Reported by group (ED US, radiology U.S., and CT, respectively)]
      • No difference in diagnostic accuracy (calculated based on ED discharge diagnosis): Sensitivity 85%, 84%, 86%, Specificity 50%, 53%, 53%
      • Significant difference in diagnostic accuracy (calculated from the results of the initial imaging method only): Sensitivity 54%, 57%, 88%, Sensitivity 71%, 73%, 58%
      • Crossover rates (patients receiving additional imaging tests) 40.7%, 27.0%, 5.1%
3. Methods:
  • Multicenter, prospective, randomized trial analyzing 2758 patients with a suspected primary diagnosis of nephrolithiasis
  • Randomized to 1 of 3 arms (point-of-care U.S. in ED, radiology department U.S., or non-contrast CT)
  • Patients received the initial imaging test to which they were assigned, but could receive additional imaging as indicated (determined by the treating physician)
  • Data collected from medical records and patient surveys at 3, 7, 30, 90, and 180 days after randomization
  • Gold standard: patients reporting the passing of a stone, or stone was surgically removed
4. Limits:
  • The choice of gold standard was questionable. Only ~33% of the patients in the study had a confirmed diagnosis according to the gold standard, causing the diagnostic accuracy results to be inaccurate and unreliable.
  • Patients, physicians, and investigators were not blinded to study arm assignment.
  • The generalizability limits applicability to large academic EDs, in non-pregnant, non-obese adults ages 18-76, who have a suspected primary diagnosis of nephrolithiasis. (Other study exclusion criteria: single kidney, post-kidney transplant, or undergoing dialysis).
  • Emergency Physicians involved in the study were trained and certified in point-of-care U.S.; results may vary based on level of ultrasound training.
  • The study protocol did not include specific U.S. criteria used for diagnosis of nephrolithiasis or reasons cited for ordering additional imaging. (Was more imaging ordered because there were no definitive findings of nephrolithiasis on U.S. despite high suspicion for a stone, extra characterization of a stone found on U.S. was needed, or the physicians were trying to assess for an alternate diagnosis?)
5. Additional Info:
  • Dr. Nelson, in addition to identifying issues with the methods of the study (namely the poor choice of gold standard), still advocates for diagnosis by CT

  • He does not believe the results showed any relevant difference between the groups (patient outcomes, cumulative radiation over 6 months, length of stay, and costs were either the same or there was no practical difference). He stated that even though the US patients were spared radiation at the initial visit, there was still significant crossover, and these patients likely received a CT within 6 months after discharge. Additionally, he pointed out that urologists/surgeons would likely want to see CT results when seeing patients for follow-up after ED discharge. So why not just get the CT?

6. Author: Dr. Kara Samsel