Ultrasound Of The Hepatobiliary System
Ultrasound Of The Hepatobiliary System
Focused BUS of the hepatobiliary system is well-suited for ED investigations of suspected biliary disease. Gallbladder disease is endemic in our population; approximately 10% of adults have gallstones, although the prevalence varies with age, sex, and ethnicity. After age 60, 10% to 15% of men and 20% to 40% of women have gallstones.110 Acute cholecystitis accounts for 3% to 9% of hospital admissions for acute abdominal pain, and the current practice standard is early cholecystectomy, making it an important diagnosis.
Nonetheless, the diagnosis of cholecystitis cannot be based on clinical examination and laboratory findings alone. One meta-analysis reported that no clinical or laboratory finding (including leukocytosis, fever, or Murphy’s sign) had a sufficiently high-positive or low-negative likelihood ratio to rule in or rule out acute cholecystitis.111
The most commonly used imaging modality in suspected cholecystitis is right upper quadrant (RUQ) ultrasound. (See Figures 14 and 15) Radiology-performed ultrasound has good sensitivity (88% to 94%) and specificity (78% to 80%) and is more convenient than radionuclide scanning, without the radiation exposure of CT.110 In comparison with comprehensive radiology-performed ultrasound, emergency clinician–performed focused RUQ ultrasound describes a focused ultrasound performed at the patient’s bedside and designed to answer targeted questions. It has excellent comparative sensitivity and specificity, can be performed and interpreted at the bedside, and has been shown to decrease ED length of stay.
Focused Ultrasound Of The Right Upper Quadrant
Although there are many sonographic criteria for acute cholecystitis (including gallstones, sonographic Murphy’s sign, gallbladder wall thickening greater than 4 mm, pericholecystic fluid, and common bile duct dilation), gallstones are present in over 90% of cases of acute cholecystitis.112 A radiology-performed study of 497 patients found the combination of gallstones with a positive sonographic Murphy’s sign had a positive predictive value of 92%, and the combination of gallstones with a thickened gallbladder wall had a positive predictive value of 95% in diagnosing acute cholecystitis.113 Hence, many studies of ED ultrasound of the gallbladder have focused on the presence of gallstones. This finding, along with a sonographic Murphy’s sign or thickened gallbladder wall, can then be considered in conjunction with the clinical presentation and laboratory findings.
Emergency clinicians are adept at finding gallstones on BUS. In a study of 109 patients with suspected biliary disease in the ED, emergency physicians (minimally trained attending physicians and residents) demonstrated a sensitivity of 96% and specificity of 88% in diagnosing cholelithiasis on ultrasound compared with the radiology-performed ultrasound.114 These emergency physicians were more accurate than radiologists in assessing for sonographic Murphy’s sign (as compared with pathologic specimens of acute cholecystitis), and the average length of the emergency physician– performed study was less than 10 minutes. In a similar study of 116 ED patients suspected of biliary disease, ultrasound performed by 15 emergency medicine attending physicians with various amounts of prior training had a sensitivity of 92% and specificity of 78% for cholelithiasis compared with radiology-performed ultrasound.115 They also noted a sensitivity of 91% and specificity of 66% for diagnosing acute cholecystitis (using stones and positive Murphy’s sign) compared with clinical follow-up. Although ED clinicians demonstrate excellent ability to find gallstones, the presence of gallstones and sonographic Murphy’s sign on emergency clinician–performed BUS should be considered within the larger clinical context of each individual patient (including physical examination and laboratory findings).
Learning Curve For Bedside Ultrasound
As in all cases of BUS, the performance and interpretation of the findings are operator-dependent. Currently, ACEP recommends 25 to 50 documented and reviewed cases to become clinically competent.1 There is some literature to support these recommendations. Gaspari et al reviewed 352 RUQ ultrasound studies by emergency medicine residents and attendings in an academic ED for both technical and interpretive errors.116 They found that the number of poor-quality ultrasound scans decreased after the operator had performed 7 examinations and that sonographers who had performed over 25 ultrasound examinations had an excellent level of agreement with the expert over-reads for detecting cholelithiasis (kappa = 0.92). Jang et al evaluated the learning curve for resident-performed RUQ ultrasound based on a gold standard of radiology-performed RUQ ultrasound/CT or pathology results and found the sensitivity and specificity for cholelithiasis or cholecystitis increased from 83% to 96% and from 88% to 100%, respectively, after residents performed 20 scans.117
Length Of Stay In The Emergency Department
One of the benefits of emergency clinician–performed BUS is the potential for expedited patient flow. A retrospective review of 1252 cases of suspected cholecystitis demonstrated that a bedside RUQ ultrasound performed by emergency physicians versus radiologyperformed ultrasound decreased length of stay by 7% (22 min) overall and 15% (52 min) during evening or nighttime hours.118
Focused ED biliary ultrasound can answer key clinical questions, such as whether gallstones or the sonographic Murphy’s sign are present, and that information can then be incorporated into the clinical context of the patient’s presentation. Studies demonstrate that emergency clinicians can achieve ultrasound results with reasonable sensitivity and specificity after a brief learning curve. Bedside biliary ultrasound has the potential to improve patient flow and decrease ED length of stay.
James Q. Hwang; Heidi Harbison Kimberly; Andrew S. Liteplo; Dana Sajed
March 2, 2011