A renal ultrasound (RUS) is mandatory in suspected renal colic (RC), acute pyelonephritis (AP) and acute renal failure (ARF) in search of hydronephrosis because management would be altered. A review on point-of-care ultrasound (PoCUS) found that sensitivity ranged from 72 to 97% and specificity from 73 to 83% for the presence of hydronephrosis . Emergency Medicine Societies promote usage of PoCUS in suspected renal colic [1, 4, 10].
The training of certified Emergency Physicians (EP) with no prior ultrasound (US) experience remains debated. In our institution, such EP participates to a 16-h training program over a 2-day period (USLS-BL1 endorsed by WINFOCUS International). The program includes operation of ultrasound device, interpretation of normal and pathological images to assess hydronephrosis, free peritoneal and pericardial fluid, proximal deep venous thrombosis, pulmonary and first-grade cardiac ultrasound. Approximately half of the time is spent performing imaging under supervision. The aim of this prospective observational survey was to assess the accuracy of renal PoCUS after this course compared with radiologist’s RUS (RRUS) as a gold standard.
Patients and methods
This was a prospective study of a convenience sample of patients with presumed RC, AP or documented ARF. It was undertaken in the ED of a tertiary teaching hospital with an annual census of 75,000 from August 2014 to March 2015. This study was approved by the Ethics Committee of Nantes University Hospital (reference RC15_0443).
The inclusion criteria for patients were a suspected RC, AP or documented ARF in patients older than 18 years of age. Exclusion criteria were pregnancy, RRUS nearly completed, documented end of life precluding further investigation. Patients for whom RRUS was not performed were secondarily excluded.
Participating EP were recruited in our ED. Inclusion criteria were the absence of previous POCUS exposure before participation to our study, in particular, no POCUS course during their medical school nor during their EM residency. They committed themselves to not follow another POCUS training until conclusion of the study.
After inclusion, information and consent to participate, a PoCUS was performed. A RRUS was then realized, the radiologist being blind to PoCUS result. Only the RRUS result was used for the management of the patients.
Using a Philips CX50 (Philips, Netherlands) with a 3.5–5 MHz curved array probe, EP obtained images of both kidneys. They completed a reporting form including demographic data, the presence or absence of hydronephrosis for each kidney. It was defined as a dilatation of the collective system. Finally, the difficulty for the PoCUS was assessed.
Formal RRUS was performed by radiologist with usual devices in the radiology department. A report was then filled with the same items.
The objective of this study was to assess the accuracy of renal PoCUS after a brief course compared with radiologist’s RUS (RRUS) as a gold standard. As a part of our policy, computed tomography is not performed in this clinical setting. The main objective was sensitivity and negative predictive value (NPV) of PoCUS. Secondary objectives were concordance explored by Kappa coefficient, specificity, positive predictive value (PPV) and likelihood ratios. The required number of subjects for sensitivity 0.9 with alpha risk 0.05 and beta 0.10 was 38.
Values stored in Microsoft Excel™ were analyzed with Graphpad™. 95% confidence intervals were calculated for sensitivity, specificity, NPV, PPV, likelihood ratios and concordance.