Diagnosis of appendicitis by bedside ultrasound in the ED

Abstract

Background

Computed tomography (CT) has largely become standard of care for diagnosing appendicitis at the expense of increased patient radiation exposure, cost, and time to surgical intervention. To date, there are very limited data on the accuracy of bedside ultrasound (BUS) for the diagnosis of appendicitis in adults.

Objective

The objective of this study is to evaluate test characteristics of BUS for diagnosis of acute appendicitis in the emergency department.

Methods

Data were prospectively collected on 97 cases of suspected appendicitis, which had BUS performed by trained residents with attending supervision between August 2011 and November 2013. All BUS interpretation and additional diagnostic imaging were left to the discretion of the physician or surgical consultants. A blinded ultrasound fellowship-trained physician reviewed all images after clinical treatment. Bedside ultrasound findings and patient outcomes were reported.

Results

A total of 97 adult cases underwent diagnostic ultrasound scans for suspected appendicitis. Of 97 cases, 34 had acute appendicitis by surgery/pathology report. Twenty-four BUS were positive for acute appendicitis and 11 were nondiagnostic. Of 24 positive ultrasounds, 23 had appendicitis on pathology report. There was 1 false-positive result, yielding a sensitivity of 67.65% (95% confidence limits, 49.5%-82.6%) and a specificity of 98.41% (95% confidence limits, 91.4%-99.7%). Of 23 positive BUS, 12 cases went to the Operating Room without an abdominal CT yielding a 12% reduction in CT utilization. If all positive BUS went to the OR without a CT scan, this would yield a 24% reduction in CT utilization.

Conclusions

Bedside ultrasound may be an appropriate initial test to evaluate patients with suspected acute appendicitis in the emergency department.

Introduction

Appendicitis is the most common surgical abdominal emergency worldwide with more than 250 000 people diagnosed annually, and 7% of the population having the disease in their lifetimes [1]. Prompt diagnosis and treatment of acute appendicitis are important, as it is believed to reduce the risk of perforation, which is associated with greater morbidity and cost of care [2], [3]. The clinical diagnosis of acute appendicitis can be complicated by an atypical presentation and a differential that can include gallbladder disease, urinary tract, and gynecologic pathologies [2], [4]. Thus, imaging studies remain an essential part of the diagnostic process in a substantial proportion of cases of undifferentiated abdominal pain, where appendicitis is a concern.

Computed tomography (CT) is considered by many to be the criterion standard in the diagnosis of acute appendicitis with sensitivities and specificities of 72% to 97% and 91% to 99%, respectively, and a positive predictive value (PPV) of 92% to 98% and negative predictive value of 95% to 100% [5], [6]. One of the clear disadvantages of CT is the potential risk of increased malignancy rates associated with ionizing radiation exposure, particularly among children and young adults. [7], [8] Currently, the estimated lifetime associated risk of radiation-induced malignancy from CT is 0.3%, and the cumulative effect of multiple CT examinations multiplies this risk [7], [8]. It is estimated that between 0.7% to 2.0% of all cancers today are caused by CT radiation exposure [7], [8].

Bedside ultrasound (BUS) is an evolving area of clinical imaging in which clinicians perform ultrasound examinations at the patient's bedside and make interpretations in real time. By performing ultrasound examinations at the bedside, imaging can be completed faster and with less cost to the patient [9]. Bedside ultrasound for appendicitis can be typically performed in 5 minutes and has produced results similar to the traditional ultrasound examinations completed by a radiologist with sensitivities of 65% to 96.4%, specificities of 67.6% to 99%, and PPVs of 84% to 98% [10], [11], [12] Because of its high specificity and high PPV, BUS is used by trained providers in many emergency departments (EDs), including the University of Utah, as an initial examination to evaluate for appendicitis. Typically, if the BUS is positive, the surgical service is consulted immediately; whereas, if it is negative, additional imaging is obtained, or surgical evaluation or a period of observation is undertaken. There is a lack of adult literature evaluating the accuracy and effectiveness of such an approach.