Study design
This was a 1-year, single-center, prospective observational study in an emergency unit recording 19,000 visits per year.
Ethic approval statement
The study protocol was approved by ethics Committee of our institution (PV 170216), according to the Jardé law (France). The IRB (Institutional Review Board) considered that the standard of care was not modified. Indeed, in our institution, we did not have access to ultrasound performed by a radiologist. That is why CT scan was the first line examination in case of suspected nephritic colic.
Patients
Any patient aged ≥ 18 years old presenting at the emergency department with a nontraumatic pain suggesting a ureteral colic (i.e., lumbar and/or pelvic pain that suddenly appeared, with or without pollakiuria and hematuria) was considered eligible, by EP. Patients were included if their attending physician was trained in clinical ultrasound.
Physician qualification was based on the completing a 5-day theoretical and practical training session at a certified center, followed by 18 months of e-learning. This course was in accordance with the recommendations of the American College of Emergency Physicians [11].
Pregnant women and patients with the previous imaging examinations were excluded. Patients who did not have an imaging session or without imaging report were also excluded.
Clinical–biological data
After the patient interview and clinical examination, the patients received an analgesia and underwent routine blood and urinary examinations.
Ultrasound data
The EP in charge of the patient performed the ultrasound examination using an Xporte© SonoSite device (SonoSite, Bothell, WA, USA). A convex abdominal probe (3.5–5 MHz) was used, according to a longitudinal grid technique (with the probe parallel to the plane of the bed). The EP followed the two axillary lines, to analyze the epigastric region, and the under-umbilical area. This permitted analyzing both the kidneys and ureters using low longitudinal and transverse intercostal slices, to measure and compare the pyelic and caliceal cavities.
The EP searched for dilatation of the pyelocalyceal cavities,which was graded according to severity, as follow: grade 1, pyelic dilatation alone; grade 2 with confluent calyceal dilatation of > 1 cm; grade 3 same as grade 2, but with a confluent dilatation of 1.5 cm diameter; grade 4 same as grade 3, but with additional cortical thinning. Grade 3 or 4 dilatation was considered severe [12]. An equal focus was given to detect peri-renal effusion, which indicates a rupture of the excretory tract.
The proximal ureter was evaluated to detect lithiasis in the pyelo-ureteral junction. The EP also ultrasonologically examine the area next to the iliac vessels and the supra pubic region, to detect lithiasis in the iliac or pelvic ureter, or in uretero-vesical meatus (Figs. 1 and 2).
The ultrasound examination also included the detection of peritoneal effusion and measurement of the abdominal aortic caliber to exclude an aneurysm.
Once PoCUS was completed, the EP wrote a report of the examination findings, including: the degree of dilatation, presence, or absence of lithiasis including the size and location of stone, if present; and the presence or absence of perinephric fluid. Finally, the EP concluded whether the patient had “ureteral colic or not”.
CT scan data
After PoCUS performed, all patients underwent an abdominopelvic CT without contrast examination with TOSHIBA© Aquilion Prime (Canon Medical System Coroporation, Otowara, Japan), the induced dose was 213 milligray. A radiologist who was blinded to the ultrasound examination result checked for the presence or absence of pyelocaliceal dilatation, perirenal effusion, or ureteral lithiasis, reporting the location and size of the stones, if present. Finally, the radiologist concluded whether or not “the patient had renal colic”.
Ureteral colic diagnosis
The diagnosis of ureteral colic was retained when ureteral lithiasis with or without an upstream dilatation or bladder lithiasis was detected on CT. It was also retained if the expulsion of the stones had been clinically confirmed.
Judgment criteria
The primary end point of the study was the diagnostic agreement rate between PoCUS and CT.
The secondary objective was to evaluate the relationship between the result of the ultrasound examination and the treatment performed.
Statistical analysis
A physician not involved in the study, but collected the results of the examinations (PoCUS and CT scan) for analysis and comparison.
The data were analyzed using Excel © software. Quantitative variables are expressed as mean ± standard deviation. Qualitative variables are expressed as number and percentage. The performance of PoCUS in detecting of pyelocalyceal dilatation, perirenal fluid, and ureteral lithiasis was expressed as sensitivity, specificity, positive predictive value, negative predictive value, and accuracy. Accuracy was defined according to the proportion of confirmed cases, or the ratio of true positives and true negatives to the total population. Further 95% confidence intervals (95% CI) were calculated.
To assess the impact of imaging on treatment, a Fischer’s exact test was performed for severe dilatation of the urinary tract, perinephric fluid, and size and location of stones, with a significance level set at 0.05.