The impact of analgesia on the diagnostic accuracy of the sonographic Murphy's sign

Objectives Administering analgesia to patients with abdominal pain before diagnostic imaging is now accepted as standard practice. However, analgesia before diagnostic right upper quadrant ultrasound continues to be controversial for fear of masking the sonographic Murphy's sign (SMS). This study sought to evaluate the impact of analgesia on the accuracy of the SMS in predicting cholecystitis. We hypothesized that the impact of analgesia on radiologist-performed ultrasound and emergency physician (EP)-performed ultrasound would be equivalent. Methods Thirty patients presenting to the emergency department with abdominal pain were randomized to receive placebo or meperidine for the first two doses of medication. The patients underwent EP performed right upper quadrant ultrasound before and after the administration of medication, in addition to receiving a radiology department ultrasound postmedication. The presence of SMS was then compared with final hospital or pathological diagnosis. Results Eleven of 30 patients (37%) had a final diagnosis of cholecystitis and only one patient had a change in their SMS postmedication. The EP assessment for postmedication SMS had a sensitivity of 0.82 [confidence interval (CI): 0.48-0.97] and specificity of 0.95 (CI: 0.71-0.99) for cholecystitis. The radiology assessment for postmedication SMS had a sensitivity of 0.17 (CI: 0.01-0.63) and specificity of 1 (CI: 0.74-1) for cholecystitis. Conclusion This pilot study shows that analgesia does not significantly change the assessment of SMS when performed by an EP sonographer. It also suggests that EP-performed ultrasound may be more accurate in assessing this predictive sign of cholecystitis. European Journal of Emergency Medicine 17: 80-83 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.