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Emergency Ultrasound

Journal Summary

STONE Plus Score to help assess patients with suspected renal colic
Review by Josh Guttman, MD

Daniels B, Gross CP, Molinaro A, et al. STONE PLUS: Evaluation of Emergency Department Patients With Suspected Renal Colic, Using a Clinical Prediction Tool Combined With Point-of-Care Limited Ultrasonography. Ann Emerg Med. 2016;67(4):439-48.

The STONE PLUS study builds on a previously derived and internally validated clinical prediction score for the likelihood of nephrolithiasis found on a subsequent CT. The authors hypothesize that by adding point of care ultrasound of the kidneys, which they termed PLUS (Point of Care Limited Ultrasonography) to the existing STONE score (assigned points based on patient gender, race, duration of pain, presence of nausea/vomiting and presence of hematuria), the diagnostic accuracy of the new STONE PLUS score would be superior to that of the STONE score alone.

The authors prospectively enrolled 835 patients. PLUS exams were performed by physicians at various levels of training, from those doing their ultrasound rotation to ultrasound fellowship-trained emergency physicians. The addition of PLUS made the most impact for low and moderate risk patients, where moderate or severe hydronephrosis increased the specificity from 67% to 98% and 42% to 92% respectively. PLUS did not significantly alter the diagnostic accuracy of high risk patients. Additionally, patients with any degree of hydronephrosis were less likely to have acutely important alternative findings on CT (OR 0.31). The authors also found that patients with moderate or severe hydronephrosis were more likely to need urologic intervention within 90 days.

This study adds to the literature by evaluating the change in post-test probability of symptomatic nephrolithiasis when adding PLUS imaging. The authors suggest that patients with moderate to severe hydronephrosis may need CT imaging due to likelihood of intervention. They propose an algorithm where those with high probability of renal stone have a trial of pain control without imaging, while those with low to moderate risk patients undergo CT scanning. They propose using low dose CT scans for those with a moderate STONE score and hydronephrosis on PLUS.

While likelihood for intervention is important, emergency physicians are more interested in who can be discharged without a CT scan, due to radiation, cost and length of stay, as well as the likelihood of missing an important alternate diagnosis mimicking renal colic. The study did not demonstrate a group of patients who could be discharged without a CT scan, other than the high risk group who often don’t require any imaging in usual practice. The study did demonstrate a lower risk of alternate diagnoses when hydronephrosis was present. This may be a group that could be discharged without a CT scan, if the clinician was only considering a CT scan because of worry about a possible alternate diagnosis. The authors propose the use of low dose CT scan in these patients, which appears useful but is unavailable in many EDs. Overall, this study adds important data to the existing literature but both the STONE score and the STONE PLUS score would benefit from external validation before they can be routinely applied in clinical practice.

The ‘Triple Scan’ improves diagnosis in dyspneic patients
Review by Amit Bahl, MD

Mantuani D, Frazee BW, Fahimi J, et al. Point-of-Care Multi-Organ Ultrasound Improves Diagnostic Accuracy in Adults Presenting to the Emergency Department with Acute Dyspnea. West J Emerg Med. 2016;17(1):46-53.

Investigators evaluated the impact of the triple scan (cardiac, thoracic, and IVC) on diagnostic accuracy of acutely dyspneic emergency department patients. 57 patients were prospectively enrolled and the triple scan was performed immediately after history and physical. Treating physicians compared diagnoses before and after triple scan with final diagnosis based on medical record review by emergency staff. Heart failure was diagnosed in 26%, Copd/asthma in 30%, and pneumonia in 28%. The accuracy of physician interpretation increased from 53% to 77% after completing the triple scan. The triple scan improved immediate diagnostic accuracy in the acutely dyspneic patient.

The acutely dyspneic patient presents a significant diagnostic challenge for the emergency physician. Physical exam is often inaccurate and leads to misdiagnosis. This study reminds me of the dyspneic patient I saw on my last shift – extensive bilateral rales with lower extremity edema. CHF right? Wrong! Fortunately I used my POCUS skills and diagnosed pneumonia on the right and pneumothorax on the left. Clearly not what I was expecting! So how do we use ultrasound to enhance diagnostic accuracy – the triple scan (cardiac, thoracic, IVC) certainly can help improve diagnostic certainty. The investigators inclusion criteria focused on the critically ill patient with significant respiratory distress in which early diagnosis and subsequent treatment is important for a good outcome. The results of this study are similar to other papers that discuss this combined ultrasound protocol adding to the current body of literature supporting its use in undifferentiated dyspnea.

Defining a normal optic nerve sheath diameter
Review by Tomislav Jelic, MD

Goeres P, Zeiler FA, Unger B, et al. Ultrasound assessment of optic nerve sheath diameter in healthy volunteers. J Crit Care. 2016;31(1):168-71.

While less than 5 millimeters has been accepted as a cutoff for a normal optic nerve sheath diameter (ONSD), no study has actually confirmed this in a healthy population. This study aimed to define a “normal” value range for ONSD. 120 healthy adults over the age of 18 were enrolled in this study. All measurements of the ONSD were measured by a single operator, based on a well-accepted method of measuring the ONSD in two planes. The overall mean ONSD was 3.68mm. There was no difference between age, weight or height. However, a statistically significant difference was found between gender. Mean ONSD in males 3.78, compared to 3.60 of females.

So is time to ditch the 5 mm cutoff and adopt a new lower cutoff value and gender difference? Not quite yet. While this was a well done study, there are a few lingering questions. A single operator did all the scans, which questions generalizability. Secondly, no difference was observed between the transverse and longitudinal measurements and only a single measurement was taken in each plane. This is evident by the intraclass correlations between the measurements of only 0.765. It would have also been interesting to look at ethnicity as other papers looking at ONSD have noted a possible difference as well.

Consider lung ultrasound for your first (or only) diagnostic imaging in presumed pediatric pneumonia
Review by Michael Boniface, MD

Jones BP, Tay ET, Elikashvili I, et al. Feasibility and Safety of Substituting Lung Ultrasound for Chest X-ray When Diagnosing Pneumonia in Children: A Randomized Controlled Trial. Chest. 2016Feb 25. pii: S0012-3692(16)01263-0. doi: 10.1016/j.chest.2016.02.643. [Epub ahead of print]

This is an extremely well designed and executed study evaluating the accuracy and safety of clinician performed lung ultrasound (LUS) on pediatric patients presenting to the ED with signs or symptoms of pneumonia. This single-center prospective randomized controlled trial enrolled 191 children from birth to 21 years old to either an investigational group receiving LUS or a control group receiving CXR first followed by LUS. Children in the investigational group still had the option of a subsequent CXR if requested by the parents, admitting team, or if there was diagnostic uncertainty. Baseline characteristic between the two groups were the same and the primary outcome of reduction in CXR utilization was 38.8%, with a NNT of 2.5 children to avoid one CXR. The authors extrapolate that if subsequent CXR following initial LUS was not requested by admitting service, PCP, or parents, there was a potential for even greater reduction: up to 67% or a NNT of 1.5. The average time to perform the study was only 7 minutes. Secondary outcome measures showed no difference in unscheduled healthcare visits, cases of missed pneumonia (zero in both groups), or hospital admission although did show a non-significant increased use of antibiotics in the investigation group. There was a reduction of the median ED length of stay from 180 minutes to 153 minutes. What is most impressive about this study (besides the results) is the care the authors took designing it. With successful randomization, a planned interim analysis for safety, and quality assurance of all images by expert sonographers with consideration of interobserver agreement, this is just good stuff. Oh, and many of the sonologists only had a one-hour training session prior to study start.

Clinician performed duplex ultrasound for acute mesenteric ischemia: not yet ready for primetime
Review by Michael Boniface, MD

Sartini S, Calosi G, Granai C, et al. Duplex ultrasound in the early diagnosis of acute mesenteric ischemia: a longitudinal cohort multicentric study. Eur J Emerg Med. 2016 Feb 17. [Epub ahead of print] PubMed PMID: 26891086.

We’ve all been there: an elderly patient presents to the ED with pain out of proportion to examination and their workup is essentially negative. Wouldn’t it be great if we could just evaluate the superior mesenteric artery flow on bedside ultrasound and reliably rule in or out mesenteric ischemia? Well… we can’t, at least not yet. This two-center prospective observational cohort study performed in Italy tested this strategy on 45 patients over an 18-month period. All enrolled patients also had multi-detector CT with contrast for angiography as gold standard unless contraindicated by renal impairment. Abnormal clinical performed duplex ultrasound was defined as peak systolic velocity (PSV) of the celiac truck and superior mesenteric artery falling outside of their reference ranges of 90-190cm/s and 80-200cm/s, respectively. Of the 45 patients enrolled, 15 had evidence of AMI on CT, 6 of which being occlusive and 9 being nonocclusive. The authors found abnormal PSV of the celiac artery in 23/44 cases and SMA in 22/45 cases. Test characteristics were calculated for each artery individually and a combination of the two. The highest performing test result was that of an abnormal PSV in either artery, which had a sensitivity of 80% and NPV of 88.33%, missing 1 in every 8 cases. The specificity was in the range of 50-66% with a PPV of only 44.4%. For occlusive mesenteric ischemia alone, the sensitivity was actually 100%, but the clinical significance of that is uncertain. This study is limited by small sample size, DUS being performed as long as 24 hours after initial ED presentation, a single sonographer acquiring images, and lack of clinical outcome data such as surgical intervention or mortality. That being said, don’t be too critical of negative studies, they are just as important as positive ones. This is a reasonably well designed pilot study and definitely worth further investigation.

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