Study design
This prospective cohort study was carried out in the emergency ward of a general hospital center that has 19,000 admissions per year.
Ethics approval
The protocol for the study was approved by the Ethics Committee of Lourdes hospital (PV N°14244) and follows the World Medical Association’s Declaration of Helsinki. It did not require written consent since the standard treatment procedures were not altered in order to perform the study.
Patients
From January 2011 to July 2013, all patients (children and adults) presented to the emergency department with as main symptom an acute pain of the right iliac fossa were included if a physician trained in use of ultrasound was present.
Clinical and laboratory examination
The history of the patient and the clinical examination strived to characterize the surgical origin of the pain by relying on standard functional and physical symptoms (e.g., signs of occlusion or localized peritonitis, nausea, vomiting, a palpable mass, abdominal pain, rebound tenderness, etc.). Urological and/or gynecological symptoms were also probed for, depending on the symptoms. A point of care urinalysis was also performed at the admission.
Systematic common laboratory testing upon admission was composed of a blood count, a test for C-reactive protein levels, as well as a blood electrolytes test, and a test of kidney function. Depending on the patient history and clinical findings, a Human Chorionic Gonadotropin (β-HCG) test, a liver and pancreatic assessment, a hemostasis assessment, a blood group typing, or any other laboratory test deemed to be of use by the emergency physician were added.
Upon assessment of all these items, the physician had to make a suspected clinical-laboratory diagnosis: surgical pathology (i.e., requiring a surgical treatment) or medical pathology (i.e., requiring a medical treatment).
Ultrasound data
After having undergone basic training in the use of abdominal ultrasound imaging, the emergency physicians who included patients for this study had to have at least 2 years of experience with emergency ultrasound use. This was first broken down into training sessions in a certified center over 7 days and then by e-learning for 1 year. This training was based on the specifications of the American College of Emergency Physicians [22]. This course was completed by supervised training over a 6-month period that involved receiving ultrasound images with validation of the observed anomalies made by a radiologist.
Following the clinical examination and the laboratory testing, the emergency physician performed an ultrasound at the patients’ bedside (using an M Turbo miniaturized ultrasound device from FUJIFILM SONOSITE©, Bothell, WA, USA).
The examination consisted of an initial grid pattern of the abdominal cavity using a convex abdominal probe (3.5 MHz), which permitted to search peritoneal effusion, masses. A scan of the two kidneys, liver, biliary tracts and aorta was equally performed. Because of the lack of a vaginal probe, pelvic analysis was performed by an abdominal probe. The emergency physician used the surface probe (7.5 MHz) to complete the scan, guided by the site of the pain, the analysis then focused on the right iliac fossa. Gradual compression was applied as described by Ooms [23, 24]: the normal digestive structures, which contain air, disappear from the screen upon compression. Furthermore, their wall is thin, with a thickness of less than 3 mm. By contrast, an inflamed digestive tract is not compressible, and it is painful upon application of pressure, while also exhibiting a thickened wall.
Other pathological images can also be seen, such as an intra-peritoneal effusion, an obstruction syndrome, inflammatory adenopathies, and complicated ovarian cyst [25,26,27] (Fig. 1).
In all cases, the emergency physician attempted to adequately discern the appendix. A diagnosis of appendicitis was made in conjunction with more than two of the following images: a double cockade cross-sectional appearance of the appendix of more than 6 mm in diameter, ending as a sleeve in a longitudinal section, a non-compressible nature, and association or not of a peri-appendicular effusion. In case of normal appendix viewed (none of previous images), this diagnosis was excluded (Fig. 2).
Upon completion of the examination, the practitioner provided a full written report regarding the ultrasound that fully detailed all of their findings. In case of a visually diseased appendix, intestinal occlusion, or peritoneal effusion, the ultrasound indicated a surgical pathology. In case of a normal appearing appendix, or other images indicative of pathologies, the ultrasound indicated a medical pathology.
After making the clinical-laboratory diagnosis, and the ultrasound diagnosis, the emergency physician in charge of the patient could ask for an abdominal CT scan and/or the opinion of a surgeon if he deemed it necessary, in particular to decide on the continuation of the patient’s care.
Final diagnosis
The final diagnosis was the etiologic diagnosis of right iliac fossa pain (i.e., surgical or medical pathology). A surgical pathology was defined by a pathology requiring surgical treatment like laparoscopy or laparotomy which was decided and performed by the surgeon. Medical pathology was defined by a pathology requiring medical treatment (non-surgical).
Two emergency physicians who did not participate in the study made the final diagnosis by reviewing the entire medical chart of each patient, taking into account their evolution. They had to classify patients into two groups: surgical or medical pathology. In each group, the etiologic diagnosis was investigated.
For the patients who underwent surgery, the final diagnosis relied on an analysis of the surgical report and of the histological examination in case of surgical exeresis. For the patients who were hospitalized without undergoing surgery, the final diagnosis was based on the final hospitalization report. When patients were not hospitalized, they were contacted 2 months after discharge, and the diagnosis made when they left the emergency ward was then confirmed or not by their medical progress. Indeed, a surgical pathology was excluded if there was no re-hospitalization in our institution or another. In case of discrepancy between the two emergency physicians, the opinion of a surgeon from our institution could be taken into consideration.
Consequently, the performance of abdominal ultrasound was compared to the performance of clinical-laboratory examination for the diagnosis of a surgical pathology.
Statistical analyses
The quantitative variables were expressed as mean ± SD for normally distributed variables and otherwise as a median with interquartile range. Qualitative variables were expressed as numerical values and as percentages.
The diagnostic performances of the ultrasound and the clinical and laboratory examination were expressed as sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV) with their [confidence intervals at 95%]. A Youden’s index and an accuracy were calculated. The Youden’s index is defined by (sensitivity + specificity − 1), and the performance of the examination was deemed to be better when the Youden’s index is close to 1. Accuracy was defined as the percentage of properly classified cases upon completion of examinations for which the performance was tested.
The relative accuracies of the ultrasound and of the clinical-laboratory diagnosis were compared using a McNemar’s test, with a threshold for significance set at p = 0.05.
No power analysis was performed because of the absence of previous studies comparing abdominal ultrasound by emergency physician and standard examination (clinic + laboratory) in the management of right iliac fossa pain.