The sonographic Murphy sign: does analgesia matter?

Controversy exists regarding analgesia premedication prior to right upper quadrant ultrasound (RUQUS) in the setting of abdominal pain when evaluating for acute cholecystitis (AC). The purpose of this study was to examine the effect of opioid and non-opioid analgesia (OA and NOA, respectively) on the sonographic Murphy sign (maximal tenderness when an ultrasound transducer probe is pressed over the visualized gallbladder) and the radiologic accuracy of diagnosing AC.

A retrospective cohort chart review analyzed 686 adult patients in two groups and the effect on diagnosis of AC in the emergency department: those who received OA versus control and another group comparing NOA versus control.

OA resulted in an increased rate of indeterminate sonographic Murphy sign and diagnoses in the treatment group compared to control (7.9% vs. 3.0%, respectively). This resulted in 24 cases of radiology-missed AC. However, there was no statistically significant difference in false-negative AC diagnosis between the NOA group compared to control (4.6% vs. 3.7%, respectively). Patients receiving OA within 30 minutes of their RUQUS examination were more likely to be given a false-negative diagnosis compared to control (8.5% vs 3.0%, respectively). Even morphine-equivalent doses <4mg were associated with increased false-negatives compared to control (8.0% vs 3.0%, respectively).

Clinicians should consider delaying OA until after the RUQUS or consider delaying the study at least 30 minutes after the administration of OA due to increased risk of false-negative results. Additionally, our results suggest that administration of NOA is a viable alternative analgesic option for many patients without sacrificing diagnostic accuracy.