Integrating Pre-test Probability and Point-of-Care Ultrasound (POCUS) in the Emergency Department (ED) Diagnosis of Small Bowel Obstruction (SBO).

Introduction A computed tomography (CT) scan and point-of-care ultrasound (POCUS) are commonly employed for diagnosing small bowel obstructions (SBOs). Prior studies demonstrated that POCUS has 90-95% sensitivity and specificity compared with CT scanning, which is the gold standard. Unlike other imaging modalities (in which the ordering and performing clinician are not the same), POCUS-performing/interpreting sonologists must recognize the risk of confirmation bias in the POCUS application. Per Bayesian analysis, the likelihood of a diagnosis being true following a diagnostic test is based on the ordering clinician's pre-test probability and the test characteristics (sensitivity and specificity, from which positive and negative likelihood ratios can be calculated). Consequently, establishing pre-test probability is important in informing downstream diagnostic or therapeutic interventions, as pre-test probability influences post-test odds. Little research has been done on the role of POCUS sonologist's pre-test probability and actual POCUS results regarding SBO. This study assessed the role of POCUS, integrating pre-test probability and POCUS results to determine post-test odds. Methods One hundred six patients were recruited on a convenience basis and underwent POCUS and CT between April 2017 and December 2022. All sonographers were credentialed in POCUS. POCUS sonologists' pre-test probabilities and POCUS and CT results were captured, which were compared. Sensitivity, specificity, LR+, and LR- were calculated, and correlations were made between pre-test probability and POCUS and CT results.  Results POCUS exhibited a sensitivity of 92% and specificity of 90%, with a corresponding positive likelihood ratio (LR+) of 9.3 and a negative likelihood ratio (LR-) of 0.09 for diagnosing SBO. Among patients with a high pre-test probability of SBO, a negative ultrasound yielded post-test odds of 0.4%, whereas a positive POCUS yielded post-test odds of 39.6%. Among patients with a low pre-test probability, a negative POCUS resulted in post-test odds of 0%, while a positive POCUS led to post-test odds of 2.1%, yielding a number needed to scan (NNS) of ~50 to identify a patient with an SBO on CT. Conclusion This study confirmed POCUS's sensitivity and specificity of ~90-95% and a corresponding LR+ of 9.2 and LR- of 0.9. Pre-test probability substantially affected post-test odds. Patients with a high pre-test probability and a positive POCUS had post-test odds of 39.6 and should have a confirmatory CT, while those with a negative POCUS have very low post-test odds and very likely will not benefit from CT. Patients with low pre-test probability and a positive POCUS have post-test odds of 2.1%, similar to the Wells Score and HEART score; such patients may not benefit from a CT, though clinicians should use their judgment/discretion. Patients with a low pre-test probability and a negative POCUS have post-test odds of 0% and should not have a CT. Among low pre-test probability patients, the NNS was ~50 to identify patients with an SBO on CT.

Patella Fracture Identified Using Point-of-care Ultrasound.

A 49-year-old female fell from standing. Her right knee extended into the air. She had acute right knee pain preventing weight-bearing. Her knee was most comfortable fully-extended. She could not flex it due to pain, nor extend it against resistance. Tenderness and a horizontal defect were noted over the anterior knee. Bedside ultrasound demonstrated a horizontally-fractured patella (confirmed on X-ray) with intact femoral and patellar tendons. She was put in a knee immobilizer and underwent surgery, with return to full function and activities. Ultrasound can identify patella fractures and help with early evaluation, management, and specialty referral, as well as ordering more-focused imaging. In one study, POCUS (point-of-care ultrasound) for patella fracture had 95% sensitivity, 63% specificity, 86% positive predictive value, and 83% negative predictive value. The dynamic nature of ultrasound allows a ruptured patella (87% sensitivity) or quadriceps tendon (100% sensitivity) to be excluded with high certainty.

Gonococcal Tenosynovitis Diagnosed with the Aid of Emergency Department Bedside Ultrasound.

BACKGROUND: Gonorrhea is the second most common sexually transmitted infection. Disseminated gonococcal infection (DGI) consists of gonococcal infection plus one or more of the triad of arthritis, tenosynovitis, and dermatitis. Diagnosis in the emergency department (ED) must be suspected clinically, as confirmatory tests are often not available. Point-of-care ultrasound (POCUS) can aid in diagnosis and appropriate management by identifying tenosynovitis and excluding arthritis. CASE REPORT: A 26-year-old man with multiple recent sex partners presented to the ED with slowly progressing right wrist pain and swelling over 5 days. His dorsal right wrist was swollen, with slightly decreased range of motion owing to mild pain, and no warmth, tenderness, erythema, or drainage. Multiple hemorrhagic, gray-purple blisters were noted over both hands. Serum white blood cell count was 12 × 103/µL; C-reactive protein was 30.3 mg/L. POCUS of the dorsal right wrist found no joint effusion; the extensor tendon sheath contained a large anechoic space with clear separation of the extensor tendons, suggesting a tendon sheath effusion/tenosynovitis. DGI was suspected, without septic arthritis. The patient was admitted and treated with ceftriaxone and azithromycin. Gonococcus grew from blood cultures and pharyngeal swabs. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: DGI must be suspected clinically, as confirmatory tests are often not available in the ED. Not all patients present with arthritis, tenosynovitis, and dermatitis. It is often difficult to differentiate tenosynovitis from arthritis. POCUS can aid in diagnosis by identifying tenosynovitis (vs. arthritis or simple soft-tissue swelling), allowing timely appropriate DGI diagnosis and management, and, importantly, averting unnecessary arthrocentesis.