By Joshua Guttman, MD, FACEP, FRCPC
Measurement of the common bile duct (CBD) internal diameter is considered to be part of the standard evaluation for biliary pathology on point of care ultrasound (POCUS). However, finding the CBD can be difficult and time consuming on some patients. Previous retrospective studies have challenged the dogma of requiring CBD evaluation on all biliary point of care ultrasounds, showing that emergent biliary pathology is rarely associated with isolated CBD dilation and normal lab values. These studies suggest that in the absence of other findings on biliary POCUS and normal lab values, CBD measurement can be omitted. However, this has never been evaluated prospectively.
Lahham et al. performed a prospective observational study on a convenience sample of patients who were getting a biliary POCUS and labs for assessment of biliary pathology. Sonographers included residents, fellows and attendings. Though no specific number of scans were required in order to enroll, all had received at least a basic ultrasound training session. They recorded final diagnosis from the ED if discharged, or from hospital discharge if admitted. Patients were contacted two weeks after discharge to assess for any change in final diagnosis. The primary outcome was the diagnosis of complicated biliary pathology (requiring acute intervention) in the absence of lab abnormalities and the absence of POCUS findings other than dilated CBD. After exclusions, 158 patients were enrolled. Approximately half the patients had biliary pathology. Of those patients, only 2 were found to have an isolated dilated CBD in the absence of lab abnormalities and other POCUS findings (wall thickening, pericholecystic fluid, sonographic murphy’s sign). One case had a gallstone found on POCUS and had a radiology ultrasound indicated uncomplicated cholelithiasis. The other case was pancreatitis diagnosed based on a lipase level. There were 2 additional cases of complicated biliary pathology, found in the absence of lab abnormalities and POCUS findings. These were 2 cases of choledocholithiasis and in both these cases the CBD was normal. The authors conclude that in the absence of POCUS findings and laboratory values concerning for complicated biliary pathology, less than 2% of patients have complicated biliary pathology and therefore CBD measurement can be omitted from the standard biliary POCUS in these cases.
While this study had limitations, namely having a convenience sample of patients and including all levels of sonographers, it prospectively assessed a more “real world” context, where various levels of POCUS expertise are scanning. It is consistent with previous research in this area. While the CBD can be found and measured most of the time, it is occasionally difficult and cannot be found. Based on this study and previous research, it would be reasonable not to order a follow up study (CT or radiology ultrasound) in the ED in the absence of other POCUS findings and normal lab values when the CBD cannot be found.
By Zachary Grambos, MD
Chang ST, Jeffrey RB, Olcott EW. Three-Step Sequential Positioning Algorithm During Sonographic Evaluation for Appendicitis Increases Appendiceal Visualization Rate and Reduces CT Use. Am J Roentgenol. 2014; 203(5)1006-1012.
Appendicitis is a fairly common surgical urgency and ultrasound has continued to grow over the last several years as the first choice for imaging modality. While it has strength at ruling in this disease process, the sensitivity to rule out disease has commonly been a topic of discussion. The authors of this paper discuss a strategy to increase the sensitivity of ultrasound and to potentially decrease CT utilization.
The use of the Left Posterior Oblique (LPO) position (rotated to left approximately 45 degrees so that the left posterior side of the patient is still touching the bed) may assist in identification of a retrocecal appendix. The appendix lies in the retrocecal position in 25-65% of patients. In North America, routine sonography of the appendix is done almost solely in the supine position. This paper highlights the utility of LPO scanning when performed to identify an inflamed appendix.
This was a retrospective study that was performed over a 12 month period before and after implementation and training of sonographers to use the LPO position. Both children and adults were included in both periods to a total of almost 900 patients. Most were children. Genders were well matched. Patients were excluded if BMI was greater than 30, if there was clinical evidence of peritonitis. During period one, all patients were scanned in the supine position. During the 3 month training period, all sonographers received real time instruction and had a minimum of 25 supervised triple position studies. There were 184 scans performed during this time period. During period two, each exam began in the supine position. If the appendix was not visualized, the patient was placed into the LPO position. If the appendix was still not able to be visualized, the patient was moved back and rescanned in the supine position. Criteria for appendicitis were standard for ultrasound with diameter greater than 6mm, noncompressibility, mural hyperemia, and echogenic periappendiceal fat.
During both study periods, the incidence of appendicitis did not statistically differ. However, the proportion of ultrasound based diagnosis of appendicitis did increase significantly in the pediatric population in period 2. Adults had an increased but non-significant rate of diagnosis of CT by sonography. The rate of CT usage within 7 days after sonography also decreased from 31% in period one to 17.7% in period two (p< 0.001)
This study, while being retrospective, did raise the point of the use of the LPO position which is a free method which may increase the diagnostic accuracy of sonography both performed at the bedside and by registered sonographers. This seems like an easy way to increase the accuracy of sonography for your trainees and seems worthwhile to the radiology department if the technicians are not already scanning in this method.